Module: PngStitcher

Extended by:
Ext
Defined in:
lib/png_stitcher.rb,
lib/png_stitcher/version.rb,
ext/png_stitcher/png_stitcher.c

Defined Under Namespace

Modules: Ext

Constant Summary collapse

VERSION = 
"0.1.0"

Class Method Summary collapse

Methods included from Ext

_stitch

Class Method Details

.stitch(blobs) ⇒ Object 



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# File 'lib/png_stitcher.rb', line 9

def stitch(blobs)
  streams = []
  height = 0
  width = nil
  palette = nil

  blobs.each do |blob|
    stream = ChunkyPNG::Datastream.from_blob(blob)
    palette ||= ChunkyPNG::Palette.from_chunks(stream.palette_chunk, stream.transparency_chunk)
    header = stream.header_chunk
    width ||= header.width
    height += header.height

    raise ArgumentError, "Color Mode must be Indexed" unless header.color == ChunkyPNG::COLOR_INDEXED
    raise ArgumentError, "Pixel Depth must be 1 bit per pixel" unless header.depth == 1
    raise ArgumentError, "Interlacing must be disabled" unless header.interlace == ChunkyPNG::INTERLACING_NONE
    raise ArgumentError, "All of the images must be the same width" unless header.width == width
    raise ArgumentError, "All of the images must have the same palette" unless palette == ChunkyPNG::Palette.from_chunks(stream.palette_chunk, stream.transparency_chunk)

    streams << stream
  end

  data = _stitch(streams, width, height)

  stream = ChunkyPNG::Datastream.new
  stream.header_chunk = ChunkyPNG::Chunk::Header.new(
    width: width,
    height: height,
    color: ChunkyPNG::COLOR_INDEXED,
    depth: 1,
    interlace: 0)
  stream.palette_chunk      = palette.to_plte_chunk
  stream.transparency_chunk = palette.to_trns_chunk unless palette.opaque?

  stream.data_chunks = ChunkyPNG::Chunk::ImageData.split_in_chunks(data)
  stream.end_chunk = ChunkyPNG::Chunk::End.new
  stream.to_blob
end