class ChunkyPNG::Chunk::Physical

The Physical (pHYs) chunk specifies the intended pixel size or aspect ratio for display of the image.

@see www.w3.org/TR/PNG/#11pHYs

Constants

INCHES_PER_METER

Attributes

ppux[RW]
ppuy[RW]
unit[RW]

Public Class Methods

new(ppux, ppuy, unit = :unknown) click to toggle source
Calls superclass method ChunkyPNG::Chunk::Base::new
    # File lib/chunky_png/chunk.rb
365 def initialize(ppux, ppuy, unit = :unknown)
366   raise ArgumentError, "unit must be either :meters or :unknown" unless [:meters, :unknown].member?(unit)
367   super("pHYs")
368   @ppux, @ppuy, @unit = ppux, ppuy, unit
369 end
read(type, content) click to toggle source
    # File lib/chunky_png/chunk.rb
381 def self.read(type, content)
382   ppux, ppuy, unit = content.unpack("NNC")
383   unit = unit == 1 ? :meters : :unknown
384   new(ppux, ppuy, unit)
385 end

Public Instance Methods

content() click to toggle source

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
389 def content
390   [ppux, ppuy, unit == :meters ? 1 : 0].pack("NNC")
391 end
dpix() click to toggle source
    # File lib/chunky_png/chunk.rb
371 def dpix
372   raise ChunkyPNG::UnitsUnknown, "the PNG specifies its physical aspect ratio, but does not specify the units of its pixels' physical dimensions" unless unit == :meters
373   ppux * INCHES_PER_METER
374 end
dpiy() click to toggle source
    # File lib/chunky_png/chunk.rb
376 def dpiy
377   raise ChunkyPNG::UnitsUnknown, "the PNG specifies its physical aspect ratio, but does not specify the units of its pixels' physical dimensions" unless unit == :meters
378   ppuy * INCHES_PER_METER
379 end