Parent

ChunkyPNG::Image

ChunkyPNG::Image is an extension of the {ChunkyPNG::Canvas} class, that also includes support for metadata.

@see ChunkyPNG::Canvas

Constants

METADATA_COMPRESSION_TRESHOLD

The minimum size of bytes the value of a metadata field should be before compression is enabled for the chunk.

Attributes

metadata[RW]

@return [Hash] The hash of metadata fields for this PNG image.

Public Class Methods

from_datastream(ds) click to toggle source

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.

# File lib/chunky_png/image.rb, line 73
def self.from_datastream(ds)
  image = super(ds)
  image.metadata = ds.metadata
  return image
end
new(width, height, bg_color = ChunkyPNG::Color::TRANSPARENT, metadata = {}) click to toggle source

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

# File lib/chunky_png/image.rb, line 22
def initialize(width, height, bg_color = ChunkyPNG::Color::TRANSPARENT, metadata = {})
  super(width, height, bg_color)
  @metadata = metadata
end

Public Instance Methods

initialize_copy(other) click to toggle source

Initializes a copy of another ChunkyPNG::Image instance.

@param [ChunkyPNG::Image] other The other image to copy.

# File lib/chunky_png/image.rb, line 30
def initialize_copy(other)
  super(other)
  @metadata = other.metadata
end
metadata_chunks() click to toggle source

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

# File lib/chunky_png/image.rb, line 43
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
to_datastream(constraints = {}) click to toggle source

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

# File lib/chunky_png/image.rb, line 61
def to_datastream(constraints = {})
  ds = super(constraints)
  ds.other_chunks += metadata_chunks
  return ds
end

[Validate]

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