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

Methods

from_datastream   initialize_copy   metadata_chunks   new   to_datastream  

Constants

METADATA_COMPRESSION_TRESHOLD = 300   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)

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.

[Source]

    # 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
new(width, height, bg_color = ChunkyPNG::Color::TRANSPARENT, 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

[Source]

    # 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

Public Instance methods

initialize_copy(other)

Initializes a copy of another ChunkyPNG::Image instance.

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

[Source]

    # File lib/chunky_png/image.rb, line 30
30:     def initialize_copy(other)
31:       super(other)
32:       @metadata = other.metadata
33:     end
metadata_chunks()

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

[Source]

    # 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
to_datastream(constraints = {})

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

[Source]

    # 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

[Validate]