Class | ChunkyPNG::Image |
In: |
lib/chunky_png/image.rb
|
Parent: | Canvas |
ChunkyPNG::Image is an extension of the {ChunkyPNG::Canvas} class, that also includes support for metadata.
@see ChunkyPNG::Canvas
METADATA_COMPRESSION_TRESHOLD | = | 300 | The minimum size of bytes the value of a metadata field should be before compression is enabled for the chunk. |
metadata | [RW] | @return [Hash] The hash of metadata fields for this PNG image. |
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 73: def self.from_datastream(ds) 74: image = super(ds) 75: image.metadata = ds.metadata 76: return image 77: end
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 22: def initialize(width, height, bg_color = ChunkyPNG::Color::TRANSPARENT, metadata = {}) 23: super(width, height, bg_color) 24: @metadata = metadata 25: end
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 30: def initialize_copy(other) 31: super(other) 32: @metadata = other.metadata 33: 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
# File lib/chunky_png/image.rb, line 43 43: def metadata_chunks 44: metadata.map do |key, value| 45: if value.length >= METADATA_COMPRESSION_TRESHOLD 46: ChunkyPNG::Chunk::CompressedText.new(key, value) 47: else 48: ChunkyPNG::Chunk::Text.new(key, value) 49: end 50: end 51: 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
# File lib/chunky_png/image.rb, line 61 61: def to_datastream(constraints = {}) 62: ds = super(constraints) 63: ds.other_chunks += metadata_chunks 64: return ds 65: end