module ChunkyPNG::Canvas::StreamImporting

def from_abgr_stream(width, height, stream)
  string = stream.respond_to?(:read) ? stream.read(4 * width * height) : stream.to_s[0, 4 * width * height]
  new(width, height, string.unpack("V*"))
end

def from_bgr_stream(width, height, stream)
  string = ChunkyPNG::EXTRA_BYTE.dup # Add a first byte to the first BGR triple.
  string << (stream.respond_to?(:read) ? stream.read(3 * width * height) : stream.to_s[0, 3 * width * height])
  pixels = string.unpack("@1#{"XV" * (width * height)}").map { |color| color | 0x000000ff }
  new(width, height, pixels)
end

def from_rgb_stream(width, height, stream)
  string = stream.respond_to?(:read) ? stream.read(3 * width * height) : stream.to_s[0, 3 * width * height]
  string << ChunkyPNG::EXTRA_BYTE # Add a fourth byte to the last RGB triple.
  unpacker = "NX" * (width * height)
  pixels = string.unpack(unpacker).map { |color| color | 0x000000ff }
  new(width, height, pixels)
end

def from_rgba_stream(width, height, stream)
  string = stream.respond_to?(:read) ? stream.read(4 * width * height) : stream.to_s[0, 4 * width * height]
  new(width, height, string.unpack("N*"))
end