module ChunkyPNG::Canvas::PNGEncoding

def to_datastream(constraints = {})

Other tags:
    See: ChunkyPNG::Canvas::PNGEncoding#determine_png_encoding -

Returns:
  • (ChunkyPNG::Datastream) - The PNG datastream containing the encoded canvas.

Options Hash: (**constraints)
  • :bit_depth (Fixnum) -- The bit depth to use. This option is only used
  • :compression (Fixnum) -- The compression level for Zlib. This can be a
  • :interlace (true, false) -- Whether to use interlacing.
  • :color_mode (Fixnum) -- The color mode to use. Use one of the

Parameters:
  • constraints (Hash, Symbol) -- The constraints to use when encoding the canvas. 
def to_datastream(constraints = {})
  encoding = determine_png_encoding(constraints)
  ds = Datastream.new
  ds.header_chunk = Chunk::Header.new(:width => width, :height => height,
      :color => encoding[:color_mode], :depth => encoding[:bit_depth], :interlace => encoding[:interlace])
  if encoding[:color_mode] == ChunkyPNG::COLOR_INDEXED
    ds.palette_chunk      = encoding_palette.to_plte_chunk
    ds.transparency_chunk = encoding_palette.to_trns_chunk unless encoding_palette.opaque?
  end
  data           = encode_png_pixelstream(encoding[:color_mode], encoding[:bit_depth], encoding[:interlace], encoding[:filtering])
  ds.data_chunks = Chunk::ImageData.split_in_chunks(data, encoding[:compression])
  ds.end_chunk   = Chunk::End.new
  return ds
end