/usr/lib/ruby/vendor_ruby/chunky_png/image.rb is in ruby-chunky-png 1.2.8-1.
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# ChunkyPNG::Image is an extension of the {ChunkyPNG::Canvas} class, that
# also includes support for metadata.
#
# @see ChunkyPNG::Canvas
class Image < Canvas
# The minimum size of bytes the value of a metadata field should be before compression
# is enabled for the chunk.
METADATA_COMPRESSION_TRESHOLD = 300
# @return [Hash] The hash of metadata fields for this PNG image.
attr_accessor :metadata
# Initializes a new ChunkyPNG::Image instance.
# @param [Integer] width The width of the new image.
# @param [Integer] height The height of the new image.
# @param [Integer] bg_color The background color of the new image.
# @param [Hash] metadata A hash of metadata fields and values for this image.
# @see ChunkyPNG::Canvas#initialize
def initialize(width, height, bg_color = ChunkyPNG::Color::TRANSPARENT, metadata = {})
super(width, height, bg_color)
@metadata = metadata
end
# Initializes a copy of another ChunkyPNG::Image instance.
#
# @param [ChunkyPNG::Image] other The other image to copy.
def initialize_copy(other)
super(other)
@metadata = other.metadata
end
# Returns the metadata for this image as PNG chunks.
#
# Chunks will either be of the {ChunkyPNG::Chunk::Text} type for small
# values (in bytes), or of the {ChunkyPNG::Chunk::CompressedText} type
# for values that are larger in size.
#
# @return [Array<ChunkyPNG::Chunk>] An array of metadata chunks.
# @see ChunkyPNG::Image::METADATA_COMPRESSION_TRESHOLD
def metadata_chunks
metadata.map do |key, value|
if value.length >= METADATA_COMPRESSION_TRESHOLD
ChunkyPNG::Chunk::CompressedText.new(key, value)
else
ChunkyPNG::Chunk::Text.new(key, value)
end
end
end
# Encodes the image to a PNG datastream for saving to disk or writing to an IO stream.
#
# Besides encoding the canvas, it will also encode the metadata fields to text chunks.
#
# @param [Hash] constraints The constraints to use when encoding the canvas.
# @return [ChunkyPNG::Datastream] The datastream that contains this image.
# @see ChunkyPNG::Canvas::PNGEncoding#to_datastream
# @see #metadata_chunks
def to_datastream(constraints = {})
ds = super(constraints)
ds.other_chunks += metadata_chunks
return ds
end
# Reads a ChunkyPNG::Image instance from a data stream.
#
# Besides decoding the canvas, this will also read the metadata fields
# from the datastream.
#
# @param [ChunkyPNG::Datastream] The datastream to read from.
def self.from_datastream(ds)
image = super(ds)
image.metadata = ds.metadata
return image
end
end
end
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