class ChunkyPNG::Chunk::Physical
The Physical (pHYs) chunk specifies the intended pixel size or aspect ratio for display of the image.
Constants
- INCHES_PER_METER
Attributes
ppux[RW]
ppuy[RW]
unit[RW]
Public Class Methods
new(ppux, ppuy, unit = :unknown)
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Calls superclass method
ChunkyPNG::Chunk::Base.new
# File lib/chunky_png/chunk.rb, line 364 def initialize(ppux, ppuy, unit = :unknown) raise ArgumentError, "unit must be either :meters or :unknown" unless [:meters, :unknown].member?(unit) super("pHYs") @ppux, @ppuy, @unit = ppux, ppuy, unit end
read(type, content)
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# File lib/chunky_png/chunk.rb, line 380 def self.read(type, content) ppux, ppuy, unit = content.unpack("NNC") unit = unit == 1 ? :meters : :unknown new(ppux, ppuy, unit) end
Public Instance Methods
content()
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Assembles the content to write to the stream for this chunk. @return [String] The binary content that should be written to the datastream.
# File lib/chunky_png/chunk.rb, line 388 def content [ppux, ppuy, unit == :meters ? 1 : 0].pack("NNC") end
dpix()
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# File lib/chunky_png/chunk.rb, line 370 def dpix raise ChunkyPNG::UnitsUnknown, "the PNG specifies its physical aspect ratio, but does not specify the units of its pixels' physical dimensions" unless unit == :meters ppux * INCHES_PER_METER end
dpiy()
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# File lib/chunky_png/chunk.rb, line 375 def dpiy raise ChunkyPNG::UnitsUnknown, "the PNG specifies its physical aspect ratio, but does not specify the units of its pixels' physical dimensions" unless unit == :meters ppuy * INCHES_PER_METER end