class HexaPDF::Content::Canvas

This class provides the basic drawing operations supported by PDF.

General Information

A canvas object is used for modifying content streams on a level higher than text. It would be possible to write a content stream by hand since PDF uses a simplified reversed polish notation for specifying operators: First come the operands, then comes the operator and no operator returns any result. However, it is easy to make mistakes this way and one has to know all operators and their operands.

This is rather tedious and therefore this class exists. It allows one to modify a content stream by invoking methods that should be familiar to anyone that has ever used a graphic API. There are methods for moving the current point, drawing lines and curves, setting the color, line width and so on.

The PDF operators themselves are implemented as classes, see Operator. The canvas class uses the Operator::BaseOperator#invoke and Operator::BaseOperator#serialize methods for applying changes and serialization, with one exception: color setters don't invoke the corresponding operator implementation but directly work on the graphics state.

PDF Graphics

Graphics Operators and Objects

There are about 60 PDF content stream operators. Some are used for changing the graphics state, some for drawing paths and others for showing text. This is all abstracted through the Canvas class.

PDF knows about five different graphics objects: path objects, text objects, external objects, inline image objects and shading objects. If none of the five graphics objects is current, the content stream is at the so called page description level (in between graphics objects).

Additionally the PDF operators are divided into several groups, like path painting or text showing operators, and such groups of operators are allowed to be used only in certain graphics objects or the page description level.

Have a look at the PDF specification (PDF1.7 s8.2) for more details.

HexaPDF tries to ensure the proper use of the operators and graphics objects and if it cannot do it, an error is raised. So if you don't modify a content stream directly but via the Canvas methods, you generally don't have to worry about the low-level inner workings.

Graphics State

Some operators modify the so called graphics state (see Content::GraphicsState). The graphics state is a collection of settings that is used during processing or creating a content stream. For example, the path painting operators don't have operands to specify the line width or the stroke color but take this information from the graphics state.

One important thing about the graphics state is that it is only possible to restore a prior state using the save and restore methods. It is not possible to reset the graphics state while creating the content stream!

Paths

A PDF path object consists of one or more subpaths. Each subpath can be a rectangle or can consist of lines and cubic bezier curves. No other types of subpaths are known to PDF. However, the Canvas class contains additional methods that use the basic path construction methods for drawing other paths like circles.

When a subpath is started, the current graphics object is changed to :path. After all path constructions are finished, a path painting method needs to be invoked to change back to the page description level. Optionally, the path painting method may be preceeded by a clipping path method to change the current clipping path (see clip_path).

There are four kinds of path painting methods:

In addition filling may be done using either the nonzero winding number rule or the even-odd rule.

Special Graphics State Methods

These methods are only allowed when the current graphics object is :none, i.e. operations are done on the page description level.

See: PDF1.7 s8, s9

Attributes

contents[R]

The serialized contents produced by the various canvas operations up to this point.

Note that the returned string may not be a completely valid PDF content stream since a graphic object may be open or the graphics state not completely restored.

See: stream_data

context[R]

The context for which the canvas was created (a HexaPDF::Type::Page or HexaPDF::Type::Form object).

current_point[R]

The current point [x, y] of the path.

This attribute holds the current point which is only valid if the current graphics objects is :path.

When the current point changes, the array is modified in place instead of creating a new array!

graphics_object[RW]

The current graphics object.

The graphics object should not be changed directly. It is automatically updated according to the invoked methods.

This attribute can have the following values:

:none

No current graphics object, i.e. the page description level.

:path

The current graphics object is a path.

:clipping_path

The current graphics object is a clipping path.

:text

The current graphics object is a text object.

See: PDF1.7 s8.2

graphics_state[R]

The Content::GraphicsState object containing the current graphics state.

The graphics state must not be changed directly, only by using the provided methods. If it is changed directly, the output will not be correct.

operators[R]

The operator name/implementation map used when invoking or serializing an operator.

stream_data[R]

A StreamData object representing the serialized contents produced by the various canvas operations.

In contrast to contents, it is ensured that an open graphics object is closed and all saved graphics states are restored when the contents of the stream data object is read. Note that this means that reading the stream data object may change the state of the canvas.

Public Class Methods

new(context) click to toggle source

Creates a new Canvas object for the given context object (either a Page or a Form).

# File lib/hexapdf/content/canvas.rb, line 194
def initialize(context)
  @context = context
  @operators = Operator::DEFAULT_OPERATORS.dup
  @graphics_state = GraphicsState.new
  @graphics_object = :none
  @font = nil
  @font_stack = []
  @serializer = HexaPDF::Serializer.new
  @current_point = [0, 0]
  @start_point = [0, 0]
  @contents = ''.b
  @stream_data = HexaPDF::StreamData.new do
    case graphics_object
    when :path, :clipping_path then end_path
    when :text then end_text
    end
    restore_graphics_state while graphics_state.saved_states?
    @contents
  end
end

Public Instance Methods

arc(cx, cy, a:, b: a, start_angle: 0, end_angle: 360, clockwise: false, inclination: 0) → canvas click to toggle source

Appends an elliptical arc to the path. The endpoint of the arc becomes the new current point.

cx

x-coordinate of the center point of the arc

cy

y-coordinate of the center point of the arc

a

Length of semi-major axis

b

Length of semi-minor axis (default: a)

start_angle

Angle in degrees at which to start the arc (default: 0)

end_angle

Angle in degrees at which to end the arc (default: 360)

clockwise

If true the arc is drawn in clockwise direction, otherwise in counterclockwise direction.

inclination

Angle in degrees between the x-axis and the semi-major axis (default: 0)

If a and b are equal, a circular arc is drawn. If the difference of the start angle and end angle is equal to 360, a full ellipse (or circle) is drawn.

If there is no current path when the method is invoked, a new path is automatically begun.

Since PDF doesn't have operators for drawing elliptical or circular arcs, they have to be approximated using Bezier curves (see curve_to). The accuracy of the approximation can be controlled using the configuration option 'graphic_object.arc.max_curves'.

Examples:

canvas.arc(0, 0, a: 10)                         # Circle at (0, 0) with radius 10
canvas.arc(0, 0, a: 10, b: 5)                   # Ellipse at (0, 0) with radii 10 and 5
canvas.arc(0, 0, a: 10, b: 5, inclination: 45)  # The above ellipse inclined 45 degrees

# Circular and elliptical arcs from 45 degrees to 135 degrees
canvas.arc(0, 0, a: 10, start_angle: 45, end_angle: 135)
canvas.arc(0, 0, a: 10, b: 5, start_angle: 45, end_angle: 135)

# Arcs from 135 degrees to 15 degrees, the first in counterclockwise direction (i.e. the
# big arc), the other in clockwise direction (i.e. the small arc)
canvas.arc(0, 0, a: 10, start_angle: 135, end_angle: 15)
canvas.arc(0, 0, a: 10, start_angle: 135, end_angle: 15, clockwise: true)

See: Content::GraphicObject::Arc

# File lib/hexapdf/content/canvas.rb, line 1064
def arc(cx, cy, a:, b: a, start_angle: 0, end_angle: 360, clockwise: false, inclination: 0)
  arc = GraphicObject::Arc.configure(cx: cx, cy: cy, a: a, b: b,
                                     start_angle: start_angle, end_angle: end_angle,
                                     clockwise: clockwise, inclination: inclination)
  arc.draw(self)
  self
end
begin_text(force_new: false) → canvas click to toggle source

Begins a new text object.

If force is true and the current graphics object is already a text object, it is ended and a new text object is begun.

See: PDF1.7 s9.4.1

# File lib/hexapdf/content/canvas.rb, line 1494
def begin_text(force_new: false)
  raise_unless_at_page_description_level_or_in_text
  end_text if force_new
  invoke0(:BT) if graphics_object == :none
  self
end
character_spacing → current_character_spacing click to toggle source
character_spacing(amount) → canvas
character_spacing(amount) { block } → canvas

The character spacing determines how much additional space is added between two consecutive characters. For horizontal writing positive values increase the distance between two characters, whereas for vertical writing negative values increase the distance.

Returns the current character spacing value (see Content::GraphicsState#character_spacing) when no argument is given. Otherwise sets the character spacing using the amount argument and returns self. The setter version can also be called in the character_spacing= form.

If the amount and a block are provided, the changed character spacing is only active during the block by saving and restoring the graphics state.

Examples:

canvas.character_spacing(0.25)
canvas.character_spacing                      # => 0.25
canvas.character_spacing = 0.5                # => 0.5

canvas.character_spacing(0.10) do
  canvas.character_spacing                    # => 0.10
end
canvas.character_spacing                      # => 0.5

See: PDF1.7 s9.3.2

# File lib/hexapdf/content/canvas.rb, line 1310
def character_spacing(amount = nil, &bk)
  gs_getter_setter(:character_spacing, :Tc, amount, &bk)
end
Also aliased as: character_spacing=
Alias for: character_spacing
circle(cx, cy, radius) → canvas click to toggle source

Appends a circle with center (cx, cy) and the given radius (in degrees) to the path as a complete subpath (drawn in counterclockwise direction). The point (center_x + radius, center_y) becomes the new current point.

If there is no current path when the method is invoked, a new path is automatically begun.

Examples:

canvas.circle(100, 100, 10)

See: arc (for approximation accuracy)

# File lib/hexapdf/content/canvas.rb, line 980
def circle(cx, cy, radius)
  arc(cx, cy, a: radius)
  close_subpath
end
clip_path(rule = :nonzero) → canvas click to toggle source

Modifies the clipping path by intersecting it with the current path.

The argument rule may either be :nonzero to use the nonzero winding number rule or :even_odd to use the even-odd rule for determining which regions lie inside the clipping path.

Note that the current path cannot be modified after invoking this method! This means that one of the path painting methods or end_path must be called immediately afterwards.

See: PDF1.7 s8.5.4

# File lib/hexapdf/content/canvas.rb, line 1209
def clip_path(rule = :nonzero)
  raise_unless_in_path
  invoke0(rule == :nonzero ? :W : :'W*')
  self
end
close_fill_stroke(rule = :nonzero) → canvas click to toggle source

Closes the last subpath and then fills and strokes the path using the given rule.

The argument rule may either be :nonzero to use the nonzero winding number rule or :even_odd to use the even-odd rule for determining which regions to fill in.

See: PDF1.7 s8.5.3

# File lib/hexapdf/content/canvas.rb, line 1175
def close_fill_stroke(rule = :nonzero)
  raise_unless_in_path_or_clipping_path
  invoke0(rule == :nonzero ? :b : :'b*')
  self
end
close_stroke → canvas click to toggle source

Closes the last subpath and then strokes the path.

See: PDF1.7 s8.5.3.1, s8.5.3.2

# File lib/hexapdf/content/canvas.rb, line 1128
def close_stroke
  raise_unless_in_path_or_clipping_path
  invoke0(:s)
  self
end
close_subpath → canvas click to toggle source

Closes the current subpath by appending a straight line from the current point to the start point of the subpath which also becomes the new current point.

# File lib/hexapdf/content/canvas.rb, line 897
def close_subpath
  raise_unless_in_path
  invoke0(:h)
  @current_point = @start_point
  self
end
color_from_specification(spec) click to toggle source

Creates a color object from the given color specification. See stroke_color for details on the possible color specifications.

# File lib/hexapdf/content/canvas.rb, line 1852
def color_from_specification(spec)
  if spec.length == 1 && spec[0].kind_of?(String)
    resources.color_space(:DeviceRGB).color(*spec[0].scan(/../).map!(&:hex))
  elsif spec.length == 1 && spec[0].respond_to?(:color_space)
    spec[0]
  else
    resources.color_space(ColorSpace.for_components(spec)).color(*spec)
  end
end
curve_to(x, y, p1:, p2:) → canvas click to toggle source
curve_to(x, y, p1:) → canvas
curve_to(x, y, p2:) → canvas

Appends a cubic Bezier curve to the current subpath starting from the current point. The end point becomes the new current point.

A Bezier curve consists of the start point, the end point and the two control points p1 and p2. The start point is always the current point and the end point is specified as x and y arguments.

Additionally, either the first control point p1 or the second control p2 or both control points have to be specified (as arrays containing two numbers). If the first control point is not specified, the current point is used as first control point. If the second control point is not specified, the end point is used as the second control point.

Examples:

canvas.curve_to(100, 100, p1: [100, 50], p2: [50, 100])
canvas.curve_to(100, 100, p1: [100, 50])
canvas.curve_to(100, 100, p2: [50, 100])
# File lib/hexapdf/content/canvas.rb, line 846
def curve_to(x, y, p1: nil, p2: nil)
  raise_unless_in_path
  if p1 && p2
    invoke(:c, *p1, *p2, x, y)
  elsif p1
    invoke(:y, *p1, x, y)
  elsif p2
    invoke(:v, *p2, x, y)
  else
    raise ArgumentError, "At least one control point must be specified for Bézier curves"
  end
  @current_point[0] = x
  @current_point[1] = y
  self
end
draw(obj, **options) → canvas click to toggle source
draw(name, **options) → canvas

Draws the given graphic object on the canvas.

See graphic_object for information on the arguments.

Examples:

canvas.draw(:arc, cx: 10, cy: 10)
# File lib/hexapdf/content/canvas.rb, line 1105
def draw(name, **options)
  graphic_object(name, **options).draw(self)
  self
end
ellipse(cx, cy, a:, b:, inclination: 0) → canvas click to toggle source

Appends an ellipse with center (cx, cy), semi-major axis a, semi-minor axis b and an inclination from the x-axis of inclination degrees to the path as a complete subpath. The outer-most point on the semi-major axis becomes the new current point.

If there is no current path when the method is invoked, a new path is automatically begun.

Examples:

# Ellipse aligned to x-axis and y-axis
canvas.ellipse(100, 100, a: 10, b: 5)

# Inclined ellipse
canvas.ellipse(100, 100, a: 10, b: 5, inclination: 45)

See: arc (for approximation accuracy)

# File lib/hexapdf/content/canvas.rb, line 1003
def ellipse(cx, cy, a:, b:, inclination: 0)
  arc(cx, cy, a: a, b: b, inclination: inclination)
  close_subpath
end
end_marked_content_sequence → canvas click to toggle source

Ends a marked-content sequence.

See marked_content_sequence for details.

See: PDF1.7 s14.6, marked_content_sequence

# File lib/hexapdf/content/canvas.rb, line 1844
def end_marked_content_sequence
  raise_unless_at_page_description_level
  invoke0(:EMC)
  self
end
end_path → canvas click to toggle source

Ends the path without stroking or filling it.

This method is normally used in conjunction with the clipping path methods to define the clipping.

See: PDF1.7 s8.5.3.1 clip

# File lib/hexapdf/content/canvas.rb, line 1190
def end_path
  raise_unless_in_path_or_clipping_path
  invoke0(:n)
  self
end
end_text → canvas click to toggle source

Ends the current text object.

See: PDF1.7 s9.4.1

# File lib/hexapdf/content/canvas.rb, line 1507
def end_text
  raise_unless_at_page_description_level_or_in_text
  invoke0(:ET) if graphics_object == :text
  self
end
fill(rule = :nonzero) → canvas click to toggle source

Fills the path using the given rule.

The argument rule may either be :nonzero to use the nonzero winding number rule or :even_odd to use the even-odd rule for determining which regions to fill in.

Any open subpaths are implicitly closed before being filled.

See: PDF1.7 s8.5.3.1, s8.5.3.3

# File lib/hexapdf/content/canvas.rb, line 1145
def fill(rule = :nonzero)
  raise_unless_in_path_or_clipping_path
  invoke0(rule == :nonzero ? :f : :'f*')
  self
end
fill_color(*color, &block) click to toggle source

The fill color defines the color used for non-stroking operations, i.e. for filling paths.

Works exactly the same stroke_color but for the fill color. See stroke_color for details on invocation and use.

# File lib/hexapdf/content/canvas.rb, line 729
def fill_color(*color, &block)
  color_getter_setter(:fill_color, color, :rg, :g, :k, :cs, :scn, &block)
end
Also aliased as: fill_color=
fill_color=(*color, &block)
Alias for: fill_color
fill_stroke(rule = :nonzero) → canvas click to toggle source

Fills and then strokes the path using the given rule.

The argument rule may either be :nonzero to use the nonzero winding number rule or :even_odd to use the even-odd rule for determining which regions to fill in.

See: PDF1.7 s8.5.3

# File lib/hexapdf/content/canvas.rb, line 1160
def fill_stroke(rule = :nonzero)
  raise_unless_in_path_or_clipping_path
  invoke0(rule == :nonzero ? :B : :'B*')
  self
end
font → current_font click to toggle source
font(name, size: nil, **options) → canvas

Specifies the font that should be used when showing text.

A valid font size need to be provided on the first invocation, otherwise an error is raised.

Note that this method returns the font object itself, not the PDF dictionary representing the font!

If size is specified, the font_size method is invoked with it as argument. All other options are passed on to the font loaders (see HexaPDF::FontLoader) that are used for loading the specified font.

Returns the current font object when no argument is given.

Examples:

canvas.font("Times", variant: :bold, size: 12)
canvas.font                                          # => font object
canvas.font = "Times"

See: PDF1.7 s9.2.2

# File lib/hexapdf/content/canvas.rb, line 1608
def font(name = nil, size: nil, **options)
  if name
    @font = (name.respond_to?(:pdf_object) ? name : context.document.fonts.add(name, **options))
    if size
      font_size(size)
    else
      size = font_size
      raise HexaPDF::Error, "No valid font size set" if size <= 0
      invoke_font_operator(@font.pdf_object, size)
    end
    self
  else
    @font
  end
end
Also aliased as: font=
Alias for: font
font_size → font_size click to toggle source
font_size(size → canvas

Specifies the font size.

Note that an error is raised if no font has been set before!

Returns the current font size when no argument is given.

Examples:

canvas.font_size(12)
canvas.font_size                       # => 12
canvas.font_size = 12

See: PDF1.7 s9.2.2

# File lib/hexapdf/content/canvas.rb, line 1642
def font_size(size = nil)
  if size
    unless @font
      raise HexaPDF::Error, "A font needs to be set before the font size can be set"
    end
    invoke_font_operator(@font.pdf_object, size)
    self
  else
    graphics_state.font_size
  end
end
Also aliased as: font_size=
Alias for: font_size
graphic_object(obj, **options) → obj click to toggle source
graphic_object(name, **options) → graphic_object

Returns the named graphic object, configured with the given options.

If an object responding to :configure is given, it is used. Otherwise the graphic object is looked up via the given name in the configuration option 'graphic_object.map'. Then the graphic object is configured with the given options if at least one is given.

Examples:

obj = canvas.graphic_object(:arc, cx: 10, cy: 10)
canvas.draw(obj)
# File lib/hexapdf/content/canvas.rb, line 1086
def graphic_object(obj, **options)
  unless obj.respond_to?(:configure)
    obj = context.document.config.constantize('graphic_object.map', obj)
  end
  obj = obj.configure(**options) unless options.empty? && obj.respond_to?(:draw)
  obj
end
horizontal_scaling → current_horizontal_scaling click to toggle source
horizontal_scaling(percent) → canvas
horizontal_scaling(percent) { block } → canvas

The horizontal scaling adjusts the width of text character glyphs by stretching or compressing them in the horizontal direction. The value is specified as percent of the normal width.

Returns the current horizontal scaling value (see Content::GraphicsState#horizontal_scaling) when no argument is given. Otherwise sets the horizontal scaling using the percent argument and returns self. The setter version can also be called in the horizontal_scaling= form.

If the percent and a block are provided, the changed horizontal scaling is only active during the block by saving and restoring the graphics state.

Examples:

canvas.horizontal_scaling(50)                  # each glyph has only 50% width
canvas.horizontal_scaling                      # => 50
canvas.horizontal_scaling = 125                # => 125

canvas.horizontal_scaling(75) do
  canvas.horizontal_scaling                    # => 75
end
canvas.horizontal_scaling                      # => 125

See: PDF1.7 s9.3.4

# File lib/hexapdf/content/canvas.rb, line 1381
def horizontal_scaling(amount = nil, &bk)
  gs_getter_setter(:horizontal_scaling, :Tz, amount, &bk)
end
Also aliased as: horizontal_scaling=
Alias for: horizontal_scaling
Alias for: xobject
leading → current_leading click to toggle source
leading(amount) → canvas
leading(amount) { block } → canvas

The leading specifies the vertical distance between the baselines of adjacent text lines.

Returns the current leading value (see Content::GraphicsState#leading) when no argument is given. Otherwise sets the leading using the amount argument and returns self. The setter version can also be called in the leading= form.

If the amount and a block are provided, the changed leading is only active during the block by saving and restoring the graphics state.

Examples:

canvas.leading(14.5)
canvas.leading                      # => 14.5
canvas.leading = 10                 # => 10

canvas.leading(25) do
  canvas.leading                    # => 25
end
canvas.leading                      # => 10

See: PDF1.7 s9.3.5

# File lib/hexapdf/content/canvas.rb, line 1412
def leading(amount = nil, &bk)
  gs_getter_setter(:leading, :TL, amount, &bk)
end
Also aliased as: leading=
Alias for: leading
line(x0, y0, x1, y1) → canvas click to toggle source

Moves the current point to (x0, y0) and appends a line to (x1, y1) to the current path.

This method is equal to “canvas.move_to(x0, y0).line_to(x1, y1)”.

Examples:

canvas.line(10, 10, 100, 100)
# File lib/hexapdf/content/canvas.rb, line 914
def line(x0, y0, x1, y1)
  move_to(x0, y0)
  line_to(x1, y1)
end
line_cap_style → current_line_cap_style click to toggle source
line_cap_style(style) → canvas
line_cap_style(style) { block } → canvas

The line cap style specifies how the ends of stroked open paths should look like. The style parameter can either be a valid integer or one of the symbols :butt, :round or :projecting_square (see Content::LineCapStyle.normalize for details). Note that the return value is always a normalized line cap style.

Returns the current line cap style (see Content::GraphicsState#line_cap_style) when no argument is given. Otherwise sets the line cap style to the given style and returns self. The setter version can also be called in the line_cap_style= form.

If the style and a block are provided, the changed line cap style is only active during the block by saving and restoring the graphics state.

Examples:

canvas.line_cap_style(:butt)
canvas.line_cap_style               # => #<NamedValue @name=:butt, @value=0>
canvas.line_cap_style = :round      # => #<NamedValue @name=:round, @value=1>

canvas.line_cap_style(:butt) do
  canvas.line_cap_style             # => #<NamedValue @name=:butt, @value=0>
end
canvas.line_cap_style               # => #<NamedValue @name=:round, @value=1>

See: PDF1.7 s8.4.3.3

# File lib/hexapdf/content/canvas.rb, line 499
def line_cap_style(style = nil, &block)
  gs_getter_setter(:line_cap_style, :J, style && LineCapStyle.normalize(style), &block)
end
Also aliased as: line_cap_style=
Alias for: line_cap_style
line_dash_pattern → current_line_dash_pattern click to toggle source
line_dash_pattern(line_dash_pattern) → canvas
line_dash_pattern(length, phase = 0) → canvas
line_dash_pattern(array, phase = 0) → canvas
line_dash_pattern(value, phase = 0) { block } → canvas

The line dash pattern defines the appearance of a stroked path (line or curve), ie. if it is solid or if it contains dashes and gaps.

There are multiple ways to set the line dash pattern:

  • By providing a Content::LineDashPattern object

  • By providing a single Integer/Float that is used for both dashes and gaps

  • By providing an array of Integers/Floats that specify the alternating dashes and gaps

The phase (i.e. the distance into the dashes/gaps at which to start) can additionally be set in the last two cases.

A solid line can be achieved by using 0 for the length or by using an empty array.

Returns the current line dash pattern (see Content::GraphicsState#line_dash_pattern) when no argument is given. Otherwise sets the line dash pattern using the given arguments and returns self. The setter version can also be called in the line_dash_pattern= form (but only without the second argument!).

If arguments and a block are provided, the changed line dash pattern is only active during the block by saving and restoring the graphics state.

Examples:

canvas.line_dash_pattern(10)
canvas.line_dash_pattern                # => LineDashPattern.new([10], 0)
canvas.line_dash_pattern(10, 2)
canvas.line_dash_pattern([5, 3, 1], 2)
canvas.line_dash_pattern = LineDashPattern.new([5, 3, 1], 1)

canvas.line_dash_pattern(10) do
  canvas.line_dash_pattern              # => LineDashPattern.new([10], 0)
end
canvas.line_dash_pattern                # => LineDashPattern.new([5, 3, 1], 1)

See: PDF1.7 s8.4.3.5, LineDashPattern

# File lib/hexapdf/content/canvas.rb, line 614
def line_dash_pattern(value = nil, phase = 0, &block)
  gs_getter_setter(:line_dash_pattern, :d, value && LineDashPattern.normalize(value, phase),
                   &block)
end
Also aliased as: line_dash_pattern=
Alias for: line_dash_pattern
line_join_style → current_line_join_style click to toggle source
line_join_style(style) → canvas
line_join_style(style) { block } → canvas

The line join style specifies the shape that is used at the corners of stroked paths. The style parameter can either be a valid integer or one of the symbols :miter, :round or :bevel (see Content::LineJoinStyle.normalize for details). Note that the return value is always a normalized line join style.

Returns the current line join style (see Content::GraphicsState#line_join_style) when no argument is given. Otherwise sets the line join style to the given style and returns self. The setter version can also be called in the line_join_style= form.

If the style and a block are provided, the changed line join style is only active during the block by saving and restoring the graphics state.

Examples:

canvas.line_join_style(:miter)
canvas.line_join_style               # => #<NamedValue @name=:miter, @value=0>
canvas.line_join_style = :round      # => #<NamedValue @name=:round, @value=1>

canvas.line_join_style(:bevel) do
  canvas.line_join_style             # => #<NamedValue @name=:bevel, @value=2>
end
canvas.line_join_style               # => #<NamedValue @name=:round, @value=1>

See: PDF1.7 s8.4.3.4

# File lib/hexapdf/content/canvas.rb, line 533
def line_join_style(style = nil, &block)
  gs_getter_setter(:line_join_style, :j, style && LineJoinStyle.normalize(style), &block)
end
Also aliased as: line_join_style=
Alias for: line_join_style
line_to(x, y) → canvas click to toggle source

Appends a straight line segment from the current point to the given point (which becomes the new current point) to the current subpath.

Examples:

canvas.line_to(100, 100)
# File lib/hexapdf/content/canvas.rb, line 816
def line_to(x, y)
  raise_unless_in_path
  invoke2(:l, x, y)
  @current_point[0] = x
  @current_point[1] = y
  self
end
line_width → current_line_width click to toggle source
line_width(width) → canvas
line_width(width) { block } → canvas

The line width determines the thickness of a stroked path.

Returns the current line width (see Content::GraphicsState#line_width) when no argument is given. Otherwise sets the line width to the given width and returns self. The setter version can also be called in the line_width= form.

If the width and a block are provided, the changed line width is only active during the block by saving and restoring the graphics state.

Examples:

canvas.line_width(10)
canvas.line_width          # => 10
canvas.line_width = 5      # => 5

canvas.line_width(10) do
  canvas.line_width        # => 10
end
canvas.line_width          # => 5

See: PDF1.7 s8.4.3.2

# File lib/hexapdf/content/canvas.rb, line 465
def line_width(width = nil, &block)
  gs_getter_setter(:line_width, :w, width, &block)
end
Also aliased as: line_width=
Alias for: line_width
marked_content_point(tag, property_list: nil) → canvas click to toggle source

Inserts a marked-content point, optionally associated with a property list.

A marked-content point is used to identify a position in the content stream for later use by other applications. The symbol tag is used to uniquely identify the role of the marked-content point and should be registered with ISO to avoid conflicts.

The optional property_list argument can either be a valid PDF dictionary or a symbol referencing an already used property list in the resource dictionary's /Properties dictionary.

Examples:

canvas.marked_content_point(:Divider)
canvas.marked_content_point(:Divider, property_list: {Key: 'value'})

See: PDF1.7 s14.6

# File lib/hexapdf/content/canvas.rb, line 1778
def marked_content_point(tag, property_list: nil)
  raise_unless_at_page_description_level_or_in_text
  if property_list
    property_list = resources.property_list(property_list) if property_list.kind_of?(Symbol)
    invoke2(:DP, tag, resources.add_property_list(property_list))
  else
    invoke1(:MP, tag)
  end
  self
end
marked_content_sequence(tag, property_list: nil) → canvas click to toggle source
marked_content_sequence(tag, property_list: nil) { block } → canvas

Inserts a marked-content sequence, optionally associated with a property list.

A marked-content sequence is used to identify a sequence of complete graphics objects in the content stream for later use by other applications. The symbol tag is used to uniquely identify the role of the marked-content sequence and should be registered with ISO to avoid conflicts.

The optional property_list argument can either be a valid PDF dictionary or a symbol referencing an already used property list in the resource dictionary's /Properties dictionary.

If invoked without a block, a corresponding call to end_marked_content_sequence must be done. Otherwise the marked-content sequence automatically ends when the block is finished.

Although the PDF specification would allow using marked-content sequences inside text objects, this is prohibited.

Examples:

canvas.marked_content_sequence(:Divider)
# Other instructions
canvas.end_marked_content_sequence

canvas.marked_content_sequence(:Divider, property_list: {Key: 'value'}) do
  # Other instructions
end

See: PDF1.7 s14.6, end_marked_content_sequence

# File lib/hexapdf/content/canvas.rb, line 1821
def marked_content_sequence(tag, property_list: nil)
  raise_unless_at_page_description_level
  if property_list
    property_list = resources.property_list(property_list) if property_list.kind_of?(Symbol)
    invoke2(:BDC, tag, resources.add_property_list(property_list))
  else
    invoke1(:BMC, tag)
  end
  if block_given?
    yield
    end_marked_content_sequence
  end
  self
end
miter_limit → current_miter_limit click to toggle source
miter_limit(limit) → canvas
miter_limit(limit) { block } → canvas

The miter limit specifies the maximum ratio of the miter length to the line width for mitered line joins (see line_join_style). When the limit is exceeded, a bevel join is used instead of a miter join.

Returns the current miter limit (see Content::GraphicsState#miter_limit) when no argument is given. Otherwise sets the miter limit to the given limit and returns self. The setter version can also be called in the miter_limit= form.

If the limit and a block are provided, the changed miter limit is only active during the block by saving and restoring the graphics state.

Examples:

canvas.miter_limit(10)
canvas.miter_limit          # => 10
canvas.miter_limit = 5      # => 5

canvas.miter_limit(10) do
  canvas.miter_limit        # => 10
end
canvas.miter_limit          # => 5

See: PDF1.7 s8.4.3.5

# File lib/hexapdf/content/canvas.rb, line 566
def miter_limit(limit = nil, &block)
  gs_getter_setter(:miter_limit, :M, limit, &block)
end
Also aliased as: miter_limit=
Alias for: miter_limit
move_text_cursor(offset: nil, absolute: true) → canvas click to toggle source

Moves the text cursor by modifying the text and text line matrices.

If offset is not specified, the text cursor is moved to the start of the next text line using leading as vertical offset.

Otherwise, the arguments offset, which has to be an array of the form [x, y], and absolute work together:

  • If absolute is true, then the text and text line matrices are set to [1, 0, 0, 1, x, y], placing the origin of text space, and therefore the text cursor, at [x, y].

    Note that absolute has to be understood in terms of the text matrix since for the actual rendering the current transformation matrix is multiplied with the text matrix.

  • If absolute is false, then the text cursor is moved to the start of the next line, offset from the start of the current line (the origin of the text line matrix) by offset.

See: show_glyphs

# File lib/hexapdf/content/canvas.rb, line 1558
def move_text_cursor(offset: nil, absolute: true)
  begin_text
  if offset
    if absolute
      text_matrix(1, 0, 0, 1, offset[0], offset[1])
    else
      invoke2(:Td, offset[0], offset[1])
    end
  else
    invoke0(:"T*")
  end
  self
end
move_to(x, y) → canvas click to toggle source

Begins a new subpath (and possibly a new path) by moving the current point to the given point.

Examples:

canvas.move_to(100, 50)
# File lib/hexapdf/content/canvas.rb, line 799
def move_to(x, y)
  raise_unless_at_page_description_level_or_in_path
  invoke2(:m, x, y)
  @current_point[0] = @start_point[0] = x
  @current_point[1] = @start_point[1] = y
  self
end
opacity → current_values click to toggle source
opacity(fill_alpha:) → canvas
opacity(stroke_alpha:) → canvas
opacity(fill_alpha:, stroke_alpha:) → canvas
opacity(fill_alpha:, stroke_alpha:) { block } → canvas

The fill and stroke alpha values determine how opaque drawn elements will be. Note that the fill alpha value applies not just to fill values but to all non-stroking operations (e.g. images, …).

Returns the current fill alpha (see Content::GraphicsState#fill_alpha) and stroke alpha (see Content::GraphicsState#stroke_alpha) values using a hash with the keys :fill_alpha and :stroke_alpha when no argument is given. Otherwise sets the fill and stroke alpha values and returns self. The setter version can also be called in the opacity= form.

If the values are set and a block is provided, the changed alpha values are only active during the block by saving and restoring the graphics state.

Examples:

canvas.opacity(fill_alpha: 0.5)
canvas.opacity                               # => {fill_alpha: 0.5, stroke_alpha: 1.0}
canvas.opacity(fill_alpha: 0.4, stroke_alpha: 0.9)
canvas.opacity                               # => {fill_alpha: 0.4, stroke_alpha: 0.9}

canvas.opacity(stroke_alpha: 0.7) do
  canvas.opacity                             # => {fill_alpha: 0.4, stroke_alpha: 0.7}
end
canvas.opacity                               # => {fill_alpha: 0.4, stroke_alpha: 0.9}

See: PDF1.7 s11.6.4.4

# File lib/hexapdf/content/canvas.rb, line 766
def opacity(fill_alpha: nil, stroke_alpha: nil)
  if !fill_alpha.nil? || !stroke_alpha.nil?
    raise_unless_at_page_description_level_or_in_text
    save_graphics_state if block_given?
    if (!fill_alpha.nil? && graphics_state.fill_alpha != fill_alpha) ||
        (!stroke_alpha.nil? && graphics_state.stroke_alpha != stroke_alpha)
      dict = {Type: :ExtGState}
      dict[:CA] = stroke_alpha unless stroke_alpha.nil?
      dict[:ca] = fill_alpha unless fill_alpha.nil?
      dict[:AIS] = false if graphics_state.alpha_source
      invoke1(:gs, resources.add_ext_gstate(dict))
    end
    if block_given?
      yield
      restore_graphics_state
    end
    self
  elsif block_given?
    raise ArgumentError, "Block only allowed with an argument"
  else
    {fill_alpha: graphics_state.fill_alpha, stroke_alpha: graphics_state.stroke_alpha}
  end
end
polygon(x0, y0, x1, y1, x2, y2, ..., radius: 0) → canvas click to toggle source

Appends a polygon consisting of the given points to the path as a complete subpath. The point (x0, y0 + radius) becomes the new current point.

If radius is greater than 0, the corners are rounded with the given radius.

If there is no current path when the method is invoked, a new path is automatically begun.

Examples:

canvas.polygon(0, 0, 100, 0, 100, 100, 0, 100)
canvas.polygon(0, 0, 100, 0, 100, 100, 0, 100, radius: 10)
# File lib/hexapdf/content/canvas.rb, line 954
def polygon(*points, radius: 0)
  if radius == 0
    polyline(*points)
  else
    check_poly_points(points)
    move_to(*point_on_line(points[0], points[1], points[2], points[3], distance: radius))
    points.concat(points[0, 4])
    0.step(points.length - 6, 2) {|i| line_with_rounded_corner(*points[i, 6], radius) }
  end
  close_subpath
end
polyline(x0, y0, x1, y1, x2, y2, ...) → canvas click to toggle source

Moves the current point to (x0, y0) and appends line segments between all given consecutive points, i.e. between (x0, y0) and (x1, y1), between (x1, y1) and (x2, y2) and so on. The last point becomes the new current point.

Examples:

canvas.polyline(0, 0, 100, 0, 100, 100, 0, 100, 0, 0)
# File lib/hexapdf/content/canvas.rb, line 929
def polyline(*points)
  check_poly_points(points)
  move_to(points[0], points[1])
  i = 2
  while i < points.length
    line_to(points[i], points[i + 1])
    i += 2
  end
  self
end
rectangle(x, y, width, height, radius: 0) → canvas click to toggle source

Appends a rectangle to the current path as a complete subpath (drawn in counterclockwise direction), with the bottom left corner specified by x and y and the given width and height.

If radius is greater than 0, the corners are rounded with the given radius.

If there is no current path when the method is invoked, a new path is automatically begun.

The current point is set to the bottom left corner if radius is zero, otherwise it is set to (x, y + radius).

Examples:

canvas.rectangle(100, 100, 100, 50)
canvas.rectangle(100, 100, 100, 50, radius: 10)
# File lib/hexapdf/content/canvas.rb, line 880
def rectangle(x, y, width, height, radius: 0)
  raise_unless_at_page_description_level_or_in_path
  if radius == 0
    invoke(:re, x, y, width, height)
    @current_point[0] = @start_point[0] = x
    @current_point[1] = @start_point[1] = y
    self
  else
    polygon(x, y, x + width, y, x + width, y + height, x, y + height, radius: radius)
  end
end
rendering_intent → current_rendering_intent click to toggle source
rendering_intent(intent) → canvas
rendering_intent(intent) { block } → canvas

The rendering intent is used to specify the intent on how colors should be rendered since sometimes compromises have to be made when the capabilities of an output device are not sufficient. The intent parameter can be one of the following symbols:

  • :AbsoluteColorimetric

  • :RelativeColorimetric

  • :Saturation

  • :Perceptual

Returns the current rendering intent (see Content::GraphicsState#rendering_intent) when no argument is given. Otherwise sets the rendering intent using the intent argument and returns self. The setter version can also be called in the rendering_intent= form.

If the intent and a block are provided, the changed rendering intent is only active during the block by saving and restoring the graphics state.

Examples:

canvas.rendering_intent(:Perceptual)
canvas.rendering_intent                      # => :Perceptual
canvas.rendering_intent = :Saturation        # => :Saturation

canvas.rendering_intent(:Perceptual) do
  canvas.rendering_intent                    # => :Perceptual
end
canvas.rendering_intent                      # => :Saturation

See: PDF1.7 s8.6.5.8, RenderingIntent

# File lib/hexapdf/content/canvas.rb, line 653
def rendering_intent(intent = nil, &bk)
  gs_getter_setter(:rendering_intent, :ri, intent && RenderingIntent.normalize(intent), &bk)
end
Also aliased as: rendering_intent=
Alias for: rendering_intent
resources() click to toggle source

Returns the resource dictionary of the context object.

# File lib/hexapdf/content/canvas.rb, line 216
def resources
  @context.resources
end
restore_graphics_state → canvas click to toggle source

Restores the current graphics state and returns self.

Must not be invoked more times than save_graphics_state.

See: PDF1.7 s8.4.2, save_graphics_state

# File lib/hexapdf/content/canvas.rb, line 263
def restore_graphics_state
  raise_unless_at_page_description_level
  invoke0(:Q)
  @font = @font_stack.pop
  self
end
rotate(angle, origin: nil) → canvas click to toggle source
rotate(angle, origin: nil) { block } → canvas

Rotates the user space angle degrees around the coordinate system origin or around the given point and returns self.

If invoked with a block, the rotation of the user space is only active during the block by saving and restoring the graphics state.

Note that the origin of the coordinate system itself doesn't change!

origin

The point around which the user space should be rotated.

Examples:

canvas.rotate(90) do                 # Positive x-axis is now pointing upwards
  canvas.line(0, 0, 100, 0)          # Actually from (0, 0) to (0, 100)
end
canvas.line(0, 0, 100, 0)            # Again from (0, 0) to (100, 0)

canvas.rotate(90, origin: [100, 100]) do
  canvas.line(100, 100, 200, 0)      # Actually from (100, 100) to (100, 200)
end

See: transform

# File lib/hexapdf/content/canvas.rb, line 332
def rotate(angle, origin: nil, &block)
  cos = Math.cos(deg_to_rad(angle))
  sin = Math.sin(deg_to_rad(angle))

  # Rotation is performed around the coordinate system origin but points are translated so
  # that the rotated rotation origin coincides with the unrotated one.
  tx = (origin ? origin[0] - (origin[0] * cos - origin[1] * sin) : 0)
  ty = (origin ? origin[1] - (origin[0] * sin + origin[1] * cos) : 0)
  transform(cos, sin, -sin, cos, tx, ty, &block)
end
save_graphics_state → canvas click to toggle source
save_graphics_state { block } → canvas

Saves the current graphics state and returns self.

If invoked without a block a corresponding call to restore_graphics_state must be done. Otherwise the graphics state is automatically restored when the block is finished.

Examples:

# With a block
canvas.save_graphics_state do
  canvas.line_width(10)
  canvas.line(100, 100, 200, 200)
end

# Same without a block
canvas.save_graphics_state
canvas.line_width(10)
canvas.line(100, 100, 200, 200)
canvas.restore_graphics_state

See: PDF1.7 s8.4.2, restore_graphics_state

# File lib/hexapdf/content/canvas.rb, line 244
def save_graphics_state
  raise_unless_at_page_description_level
  invoke0(:q)
  @font_stack.push(@font)
  if block_given?
    yield
    restore_graphics_state
  end
  self
end
scale(sx, sy = sx, origin: nil) → canvas click to toggle source
scale(sx, sy = sx, origin: nil) { block } → canvas

Scales the user space sx units in the horizontal and sy units in the vertical direction and returns self. If the optional origin is specified, scaling is done from that point.

If invoked with a block, the scaling is only active during the block by saving and restoring the graphics state.

Note that the origin of the coordinate system itself doesn't change!

origin

The point from which the user space should be scaled.

Examples:

canvas.scale(2, 3) do                # Point (1, 1) is now actually (2, 3)
  canvas.line(50, 50, 100, 100)      # Actually from (100, 150) to (200, 300)
end
canvas.line(0, 0, 100, 0)            # Again from (0, 0) to (100, 0)

canvas.scale(2, 3, origin: [50, 50]) do
  canvas.line(50, 50, 100, 100)      # Actually from (50, 50) to (200, 300)
end

See: transform

# File lib/hexapdf/content/canvas.rb, line 371
def scale(sx, sy = sx, origin: nil, &block)
  # As with rotation, scaling is performed around the coordinate system origin but points
  # are translated so that the scaled scaling origin coincides with the unscaled one.
  tx = (origin ? origin[0] - origin[0] * sx : 0)
  ty = (origin ? origin[1] - origin[1] * sy : 0)
  transform(sx, 0, 0, sy, tx, ty, &block)
end
show_glyphs(glyphs) → canvas click to toggle source

Low-level method for actually showing text on the canvas.

The argument glyphs needs to be a an array of glyph objects valid for the current font, optionally interspersed with numbers for kerning.

Text is always shown at the current position of the text cursor, i.e. the origin of the text matrix. To move the text cursor to somewhere else use move_text_cursor before calling this method.

The text matrix is updated to correctly represent the graphics state after the invocation.

This method is usually not invoked directly but by higher level methods like text.

# File lib/hexapdf/content/canvas.rb, line 1702
def show_glyphs(glyphs)
  return if glyphs.empty?
  raise_unless_font_set
  begin_text

  result = [''.b]
  offset = 0
  glyphs.each do |item|
    if item.kind_of?(Numeric)
      result << item << ''.b
      offset -= item * graphics_state.scaled_font_size
    else
      encoded = @font.encode(item)
      result[-1] << encoded

      offset += item.width * graphics_state.scaled_font_size +
        graphics_state.scaled_character_spacing
      offset += graphics_state.scaled_word_spacing if encoded == " "
    end
  end

  invoke1(:TJ, result)
  graphics_state.tm.translate(offset, 0)
  self
end
show_glyphs_only(glyphs) → canvas click to toggle source

Same operation as with show_glyphs but without updating the text matrix.

This method should only be used by advanced text layouting algorithms which perform the necessary calculations themselves!

Warning: Since this method doesn't update the text matrix, all following results from text_cursor and other methods using the current text matrix are invalid until the next call to text_matrix or end_text.

# File lib/hexapdf/content/canvas.rb, line 1739
def show_glyphs_only(glyphs)
  return if glyphs.empty?
  raise_unless_font_set
  begin_text

  simple = true
  result = [last = ''.b]
  glyphs.each do |item|
    if item.kind_of?(Numeric)
      simple = false
      result << item << (last = ''.b)
    else
      last << @font.encode(item)
    end
  end

  simple ? serialize1(:Tj, result[0]) : serialize1(:TJ, result)
  self
end
skew(a, b, origin: nil) → canvas click to toggle source
skew(a, b, origin: nil) { block } → canvas

Skews the the x-axis by a degrees and the y-axis by b degress and returns self. If the optional origin is specified, skewing is done from that point.

If invoked with a block, the skewing is only active during the block by saving and restoring the graphics state.

Note that the origin of the coordinate system itself doesn't change!

origin

The point from which the axes are skewed.

Examples:

canvas.skew(0, 45) do                 # Point (1, 1) is now actually (2, 1)
  canvas.line(50, 50, 100, 100)       # Actually from (100, 50) to (200, 100)
end
canvas.line(0, 0, 100, 0)             # Again from (0, 0) to (100, 0)

canvas.skew(0, origin: [50, 50]) do
  canvas.line(50, 50, 100, 100)       # Actually from (50, 50) to (200, 300)
end

See: transform

# File lib/hexapdf/content/canvas.rb, line 428
def skew(a, b, origin: nil, &block)
  tan_a = Math.tan(deg_to_rad(a))
  tan_b = Math.sin(deg_to_rad(b))

  # As with rotation, skewing is performed around the coordinate system origin but points
  # are translated so that the skewed skewing origin coincides with the unskewed one.
  tx = (origin ? -origin[1] * tan_b : 0)
  ty = (origin ? -origin[0] * tan_a : 0)
  transform(1, tan_a, tan_b, 1, tx, ty, &block)
end
stroke → canvas click to toggle source

Strokes the path.

See: PDF1.7 s8.5.3.1, s8.5.3.2

# File lib/hexapdf/content/canvas.rb, line 1116
def stroke
  raise_unless_in_path_or_clipping_path
  invoke0(:S)
  self
end
stroke_color → current_stroke_color click to toggle source
stroke_color(gray) → canvas
stroke_color(r, g, b) → canvas
stroke_color(c, m, y, k) → canvas
stroke_color(string) → canvas
stroke_color(color_object) → canvas
stroke_color(array) → canvas
stroke_color(color_spec) { block } → canvas

The stroke color defines the color used for stroking operations, i.e. for painting paths.

There are several ways to define the color that should be used:

  • A single numeric argument specifies a gray color (see Content::ColorSpace::DeviceGray::Color).

  • Three numeric arguments specify an RGB color (see Content::ColorSpace::DeviceRGB::Color).

  • A string in the format “RRGGBB” where “RR” is the hexadecimal number for the red, “GG” for the green and “BB” for the blue color value also specifies an RGB color.

  • Four numeric arguments specify a CMYK color (see Content::ColorSpace::DeviceCMYK::Color).

  • A color object is used directly (normally used for color spaces other than DeviceRGB, DeviceCMYK and DeviceGray).

  • An array is treated as if its items were specified separately as arguments.

Returns the current stroke color (see Content::GraphicsState#stroke_color) when no argument is given. Otherwise sets the stroke color using the given arguments and returns self. The setter version can also be called in the stroke_color= form.

If the arguments and a block are provided, the changed stroke color is only active during the block by saving and restoring the graphics state.

Examples:

# With no arguments just returns the current color
canvas.stroke_color                        # => DeviceGray.color(0.0)

# Same gray color because integer values are normalized to the range of 0.0 to 1.0
canvas.stroke_color(102)
canvas.stroke_color(0.4)

# Specifying RGB colors
canvas.stroke_color(255, 255, 0)
canvas.stroke_color("FFFF00")

# Specifying CMYK colors
canvas.stroke_color(255, 255, 0, 128)

# Can use a color object directly
color = HexaPDF::Content::ColorSpace::DeviceRGB.color(255, 255, 0)
canvas.stroke_color(color)

# An array argument is destructured - these calls are all equal
cnavas.stroke_color(255, 255, 0)
canvas.stroke_color([255, 255, 0])
canvas.stroke_color = [255, 255, 0]

# As usual, can be invoked with a block to limit the effects
canvas.stroke_color(102) do
  canvas.stroke_color                      # => ColorSpace::DeviceGray.color(0.4)
end

See: PDF1.7 s8.6, ColorSpace

# File lib/hexapdf/content/canvas.rb, line 720
def stroke_color(*color, &block)
  color_getter_setter(:stroke_color, color, :RG, :G, :K, :CS, :SCN, &block)
end
Also aliased as: stroke_color=
Alias for: stroke_color
text(text) → canvas click to toggle source
text(text, at: [x, y]) → canvas

Shows the given text string.

If no position is provided, the text is positioned at the current position of the text cursor (the origin in case of a new text object or otherwise after the last shown text).

The text string may contain any valid Unicode newline separator and if so, multiple lines are shown, using leading for offsetting the lines.

Note that there are no provisions to make sure that all text is visible! So if the text string is too long, it will just flow off the page and be cut off.

Examples:

canvas.font('Times', size: 12)
canvas.text("This is a \n multiline text", at: [100, 100])

See: www.unicode.org/reports/tr18/#Line_Boundaries

# File lib/hexapdf/content/canvas.rb, line 1676
def text(text, at: nil)
  raise_unless_font_set
  move_text_cursor(offset: at) if at
  lines = text.split(/\u{D A}|(?!\u{D A})[\u{A}-\u{D}\u{85}\u{2028}\u{2029}]/, -1)
  lines.each_with_index do |str, index|
    show_glyphs(@font.decode_utf8(str))
    move_text_cursor unless index == lines.length - 1
  end
  self
end
text_cursor → [x, y] click to toggle source

Returns the position of the text cursor, i.e. the origin of the current text matrix.

Note that this method can only be called while the current graphic object is a text object since the text matrix is otherwise undefined.

# File lib/hexapdf/content/canvas.rb, line 1579
def text_cursor
  raise_unless_in_text
  graphics_state.tm.evaluate(0, 0)
end
text_matrix(a, b, c, d, e, f) → canvas click to toggle source

Sets the text matrix (and the text line matrix) to the given matrix and returns self.

The given values are interpreted as a matrix in the following way:

a b 0
c d 0
e f 1

Examples:

canvas.begin_text
canvas.text_matrix(1, 0, 0, 1, 100, 100)

See: PDF1.7 s9.4.2

# File lib/hexapdf/content/canvas.rb, line 1530
def text_matrix(a, b, c, d, e, f)
  begin_text
  invoke(:Tm, a, b, c, d, e, f)
  self
end
text_rendering_mode → current_text_rendering_mode click to toggle source
text_rendering_mode(mode) → canvas
text_rendering_mode(mode) { block } → canvas

The text rendering mode determines if and how glyphs are rendered. The mode parameter can either be a valid integer or one of the symbols :fill, :stroke, :fill_stroke, :invisible, :fill_clip, :stroke_clip, :fill_stroke_clip or :clip (see TextRenderingMode.normalize for details). Note that the return value is always a normalized text rendering mode value.

Returns the current text rendering mode value (see Content::GraphicsState#text_rendering_mode) when no argument is given. Otherwise sets the text rendering mode using the mode argument and returns self. The setter version can also be called in the text_rendering_mode= form.

If the mode and a block are provided, the changed text rendering mode is only active during the block by saving and restoring the graphics state.

Examples:

canvas.text_rendering_mode(:fill)
canvas.text_rendering_mode               # => #<NamedValue @name=:fill, @value = 0>
canvas.text_rendering_mode = :stroke     # => #<NamedValue @name=:stroke, @value = 1>

canvas.text_rendering_mode(3) do
  canvas.text_rendering_mode             # => #<NamedValue @name=:invisible, @value = 3>
end
canvas.text_rendering_mode               # => #<NamedValue @name=:stroke, @value = 1>

See: PDF1.7 s9.3.6

# File lib/hexapdf/content/canvas.rb, line 1448
def text_rendering_mode(m = nil, &bk)
  gs_getter_setter(:text_rendering_mode, :Tr, m && TextRenderingMode.normalize(m), &bk)
end
Also aliased as: text_rendering_mode=
Alias for: text_rendering_mode
text_rise → current_text_rise click to toggle source
text_rise(amount) → canvas
text_rise(amount) { block } → canvas

The text rise specifies the vertical distance to move the baseline up or down from its default location. Positive values move the baseline up, negative values down.

Returns the current text rise value (see Content::GraphicsState#text_rise) when no argument is given. Otherwise sets the text rise using the amount argument and returns self. The setter version can also be called in the text_rise= form.

If the amount and a block are provided, the changed text rise is only active during the block by saving and restoring the graphics state.

Examples:

canvas.text_rise(5)
canvas.text_rise                      # => 5
canvas.text_rise = 10                 # => 10

canvas.text_rise(15) do
  canvas.text_rise                    # => 15
end
canvas.text_rise                      # => 10

See: PDF1.7 s9.3.7

# File lib/hexapdf/content/canvas.rb, line 1480
def text_rise(amount = nil, &bk)
  gs_getter_setter(:text_rise, :Ts, amount, &bk)
end
Also aliased as: text_rise=
Alias for: text_rise
transform(a, b, c, d, e, f) → canvas click to toggle source
transform(a, b, c, d, e, f) { block } → canvas

Transforms the user space by applying the given matrix to the current transformation matrix and returns self.

If invoked with a block, the transformation is only active during the block by saving and restoring the graphics state.

The given values are interpreted as a matrix in the following way:

a b 0
c d 0
e f 1

Examples:

canvas.transform(1, 0, 0, 1, 100, 100) do  # Translate origin to (100, 100)
  canvas.line(0, 0, 100, 100)              # Actually from (100, 100) to (200, 200)
end
canvas.line(0, 0, 100, 100)                # Again from (0, 0) to (100, 100)

See: PDF1.7 s8.3, s8.4.4

# File lib/hexapdf/content/canvas.rb, line 294
def transform(a, b, c, d, e, f)
  raise_unless_at_page_description_level
  save_graphics_state if block_given?
  invoke(:cm, a, b, c, d, e, f)
  if block_given?
    yield
    restore_graphics_state
  end
  self
end
translate(x, y) → canvas click to toggle source
translate(x, y) { block } → canvas

Translates the user space coordinate system origin to the given x and y coordinates and returns self.

If invoked with a block, the translation of the user space is only active during the block by saving and restoring the graphics state.

Examples:

canvas.translate(100, 100) do        # Origin is now at (100, 100)
  canvas.line(0, 0, 100, 0)          # Actually from (100, 100) to (200, 100)
end
canvas.line(0, 0, 100, 0)            # Again from (0, 0) to (100, 0)

See: transform

# File lib/hexapdf/content/canvas.rb, line 397
def translate(x, y, &block)
  transform(1, 0, 0, 1, x, y, &block)
end
word_spacing → current_word_spacing click to toggle source
word_spacing(amount) → canvas
word_spacing(amount) { block } → canvas

If the font's PDF encoding supports this, the word spacing determines how much additional space is added when the ASCII space character is encountered in a text. For horizontal writing positive values increase the distance between two words, whereas for vertical writing negative values increase the distance.

Note that in HexaPDF only the standard 14 PDF Type1 fonts support this property! When using any other font, for example a TrueType font, this property has no effect.

Returns the current word spacing value (see Content::GraphicsState#word_spacing) when no argument is given. Otherwise sets the word spacing using the amount argument and returns self. The setter version can also be called in the word_spacing= form.

If the amount and a block are provided, the changed word spacing is only active during the block by saving and restoring the graphics state.

Examples:

canvas.word_spacing(0.25)
canvas.word_spacing                      # => 0.25
canvas.word_spacing = 0.5                # => 0.5

canvas.word_spacing(0.10) do
  canvas.word_spacing                    # => 0.10
end
canvas.word_spacing                      # => 0.5

See: PDF1.7 s9.3.3

# File lib/hexapdf/content/canvas.rb, line 1347
def word_spacing(amount = nil, &bk)
  gs_getter_setter(:word_spacing, :Tw, amount, &bk)
end
Also aliased as: word_spacing=
Alias for: word_spacing
xobject(filename, at:, width: nil, height: nil) → xobject click to toggle source
xobject(io, at:, width: nil, height: nil) → xobject
xobject(image_object, at:, width: nil, height: nil) → image_object
xobject(form_object, at:, width: nil, height: nil) → form_object

Draws the given XObject (either an image XObject or a form XObject) at the specified position and returns the XObject.

Any image format for which a HexaPDF::ImageLoader object is available and registered with the configuration option 'image_loader' can be used. PNG and JPEG images are supported out of the box.

If the filename or the IO specifies a PDF file, the first page of this file is used to create a form XObject which is then drawn.

The at argument has to be an array containing two numbers specifying the bottom left corner at which to draw the XObject.

If width and height are specified, the drawn XObject will have exactly these dimensions. If only one of them is specified, the other dimension is automatically calculated so that the aspect ratio is retained. If neither is specified, the width and height of the XObject are used (for images, 1 pixel being represented by 1 PDF point, i.e. 72 DPI).

Note: If a form XObject is drawn, all currently set graphics state parameters influence the rendering of the form XObject. This means, for example, that when the line width is set to 20, all lines of the form XObject are drawn with that line width unless the line width is changed in the form XObject itself.

Examples:

canvas.xobject('test.png', at: [100, 100])
canvas.xobject('test.pdf', at: [100, 100])

File.new('test.jpg', 'rb') do |io|
  canvas.xobject(io, at: [100, 200], width: 300)
end

image = document.object(5)    # Object with oid=5 is an image XObject in this example
canvas.xobject(image, at: [100, 200], width: 200, height: 300)

See: PDF1.7 s8.8, s.8.10.1

# File lib/hexapdf/content/canvas.rb, line 1258
def xobject(obj, at:, width: nil, height: nil)
  unless obj.kind_of?(HexaPDF::Stream)
    obj = context.document.images.add(obj)
  end
  return obj if obj.width == 0 || obj.height == 0

  width, height = calculate_dimensions(obj.width, obj.height,
                                       rwidth: width, rheight: height)
  if obj[:Subtype] != :Image
    width /= obj.box.width.to_f
    height /= obj.box.height.to_f
    at[0] -= obj.box.left
    at[1] -= obj.box.bottom
  end

  transform(width, 0, 0, height, at[0], at[1]) do
    invoke1(:Do, resources.add_xobject(obj))
  end

  obj
end
Also aliased as: image

Private Instance Methods

check_poly_points(points) click to toggle source

Modifies and checks the array points so that polylines and polygons work correctly.

# File lib/hexapdf/content/canvas.rb, line 2034
def check_poly_points(points)
  if points.length < 4
    raise ArgumentError, "At least two points needed to make one line segment"
  elsif points.length.odd?
    raise ArgumentError, "Missing y-coordinate for last point"
  end
end
color_getter_setter(name, color, rg, g, k, cs, scn) { || ... } click to toggle source

Utility method that abstracts the implementation of the stroke and fill color methods.

# File lib/hexapdf/content/canvas.rb, line 1962
def color_getter_setter(name, color, rg, g, k, cs, scn)
  color.flatten!
  if !color.empty?
    raise_unless_at_page_description_level_or_in_text
    color = color_from_specification(color)

    save_graphics_state if block_given?
    unless color == graphics_state.send(name)
      case color.color_space.family
      when :DeviceRGB then serialize(rg, *color.components)
      when :DeviceGray then serialize(g, *color.components)
      when :DeviceCMYK then serialize(k, *color.components)
      else
        if color.color_space != graphics_state.send(name).color_space
          serialize(cs, resources.add_color_space(color.color_space))
        end
        serialize(scn, *color.components)
      end
      graphics_state.send(:"#{name}=", color)
    end

    if block_given?
      yield
      restore_graphics_state
    end

    self
  elsif block_given?
    raise ArgumentError, "Block only allowed with arguments"
  else
    graphics_state.send(name)
  end
end
gs_getter_setter(name, op, value) { || ... } click to toggle source

Utility method that abstracts the implementation of a graphics state parameter getter/setter method with a call sequence of:

canvas.method                        # => cur_value
canvas.method(new_value)             # => canvas
canvas.method(new_value) { block }   # => canvas
name

The name (Symbol) of the graphics state parameter for fetching the value from the GraphicState.

op

The operator (Symbol) which should be invoked if the value is different from the current value of the graphics state parameter.

value

The new value of the graphics state parameter, or nil if the getter functionality is needed.

# File lib/hexapdf/content/canvas.rb, line 2014
def gs_getter_setter(name, op, value)
  if !value.nil?
    raise_unless_at_page_description_level_or_in_text
    save_graphics_state if block_given?
    if graphics_state.send(name) != value
      value.respond_to?(:to_operands) ? invoke(op, *value.to_operands) : invoke1(op, value)
    end
    if block_given?
      yield
      restore_graphics_state
    end
    self
  elsif block_given?
    raise ArgumentError, "Block only allowed with an argument"
  else
    graphics_state.send(name)
  end
end
invoke(operator, *operands) click to toggle source

Invokes the given operator with the operands and serializes it.

# File lib/hexapdf/content/canvas.rb, line 1865
def invoke(operator, *operands)
  @operators[operator].invoke(self, *operands)
  serialize(operator, *operands)
end
invoke0(operator) click to toggle source

Optimized method for zero operands.

# File lib/hexapdf/content/canvas.rb, line 1876
def invoke0(operator)
  @operators[operator].invoke(self)
  @contents << @operators[operator].serialize(@serializer)
end
invoke1(operator, op1) click to toggle source

Optimized method for one operand.

# File lib/hexapdf/content/canvas.rb, line 1882
def invoke1(operator, op1)
  @operators[operator].invoke(self, op1)
  @contents << @operators[operator].serialize(@serializer, op1)
end
invoke2(operator, op1, op2) click to toggle source

Optimized method for two operands.

# File lib/hexapdf/content/canvas.rb, line 1893
def invoke2(operator, op1, op2)
  @operators[operator].invoke(self, op1, op2)
  @contents << @operators[operator].serialize(@serializer, op1, op2)
end
invoke_font_operator(font, font_size) click to toggle source

Invokes the font operator using the given PDF font dictionary.

# File lib/hexapdf/content/canvas.rb, line 1899
def invoke_font_operator(font, font_size)
  unless graphics_state.font == font && graphics_state.font_size == font_size
    invoke(:Tf, resources.add_font(font), font_size)
  end
end
line_with_rounded_corner(x0, y0, x1, y1, x2, y2, radius) click to toggle source

Appends a line with a rounded corner from the current point. The corner is specified by the three points (x0, y0), (x1, y1) and (x2, y2) where (x1, y1) is the corner point.

# File lib/hexapdf/content/canvas.rb, line 2049
def line_with_rounded_corner(x0, y0, x1, y1, x2, y2, radius)
  p0 = point_on_line(x1, y1, x0, y0, distance: radius)
  p3 = point_on_line(x1, y1, x2, y2, distance: radius)
  p1 = point_on_line(p0[0], p0[1], x1, y1, distance: KAPPA * radius)
  p2 = point_on_line(p3[0], p3[1], x1, y1, distance: KAPPA * radius)
  line_to(p0[0], p0[1])
  curve_to(p3[0], p3[1], p1: p1, p2: p2)
end
raise_unless_at_page_description_level() click to toggle source

Raises an error unless the current graphics object is none, i.e. the page description level.

# File lib/hexapdf/content/canvas.rb, line 1922
def raise_unless_at_page_description_level
  end_text if graphics_object == :text
  unless graphics_object == :none
    raise HexaPDF::Error, "Operation only allowed if there is no current graphics object"
  end
end
raise_unless_at_page_description_level_or_in_path() click to toggle source

Raises an error unless the current graphics object is none or a path object.

# File lib/hexapdf/content/canvas.rb, line 1938
def raise_unless_at_page_description_level_or_in_path
  end_text if graphics_object == :text
  unless graphics_object == :none || graphics_object == :path
    raise HexaPDF::Error, "Operation only allowed if current graphics object is a " \
      "path object or if there is no current object"
  end
end
raise_unless_at_page_description_level_or_in_text() click to toggle source

Raises an error unless the current graphics object is none or a text object.

# File lib/hexapdf/content/canvas.rb, line 1930
def raise_unless_at_page_description_level_or_in_text
  unless graphics_object == :none || graphics_object == :text
    raise HexaPDF::Error, "Operation only allowed if current graphics object is a " \
      "text object or if there is no current object"
  end
end
raise_unless_font_set() click to toggle source

Raises an error unless a font has been set.

# File lib/hexapdf/content/canvas.rb, line 1955
def raise_unless_font_set
  unless @font
    raise HexaPDF::Error, "Operation only allowed if a font is set"
  end
end
raise_unless_in_path() click to toggle source

Raises an error unless the current graphics object is a path.

# File lib/hexapdf/content/canvas.rb, line 1906
def raise_unless_in_path
  unless graphics_object == :path
    raise HexaPDF::Error, "Operation only allowed if current graphics object is a path"
  end
end
raise_unless_in_path_or_clipping_path() click to toggle source

Raises an error unless the current graphics object is a path or a clipping path.

# File lib/hexapdf/content/canvas.rb, line 1913
def raise_unless_in_path_or_clipping_path
  unless graphics_object == :path || graphics_object == :clipping_path
    raise HexaPDF::Error, "Operation only allowed if current graphics object is a " \
      "path or clipping path"
  end
end
raise_unless_in_text() click to toggle source

Raises an error unless the current graphics object is a text object.

# File lib/hexapdf/content/canvas.rb, line 1947
def raise_unless_in_text
  unless graphics_object == :text
    raise HexaPDF::Error, "Operation only allowed if current graphics object is a " \
      "text object"
  end
end
serialize(operator, *operands) click to toggle source

Serializes the operator with the operands to the content stream.

# File lib/hexapdf/content/canvas.rb, line 1871
def serialize(operator, *operands)
  @contents << @operators[operator].serialize(@serializer, *operands)
end
serialize1(operator, op1) click to toggle source

Optimized method for one operand.

# File lib/hexapdf/content/canvas.rb, line 1888
def serialize1(operator, op1)
  @contents << @operators[operator].serialize(@serializer, op1)
end