module ChunkyPNG::Canvas::StreamImporting

Methods to quickly load a canvas from a stream, encoded in RGB, RGBA, BGR or ABGR format.

Public Instance Methods

from_abgr_stream(width, height, stream) click to toggle source

Creates a canvas by reading pixels from an ARGB formatted stream with a provided with and height.

Every pixel should be represented by 4 bytes in the stream, in the correct ARGB order. This format is almost like the internal representation of a canvas object, so this kind of stream can be read extremely quickly.

@param [Integer] width The width of the new canvas. @param [Integer] height The height of the new canvas. @param [#read, String] stream The stream to read the pixel data from. @return [ChunkyPNG::Canvas] The newly constructed canvas instance.

# File lib/chunky_png/canvas/stream_importing.rb, line 71
def from_abgr_stream(width, height, stream)
  string = stream.respond_to?(:read) ? stream.read(4 * width * height) : stream.to_s[0, 4 * width * height]
  self.new(width, height, string.unpack("V*"))
end
from_bgr_stream(width, height, stream) click to toggle source

Creates a canvas by reading pixels from an BGR formatted stream with a provided with and height.

Every pixel should be represented by 3 bytes in the stream, in the correct BGR order. This format closely resembles the internal representation of a canvas object, so this kind of stream can be read extremely quickly.

@param [Integer] width The width of the new canvas. @param [Integer] height The height of the new canvas. @param [#read, String] stream The stream to read the pixel data from. @return [ChunkyPNG::Canvas] The newly constructed canvas instance.

# File lib/chunky_png/canvas/stream_importing.rb, line 53
def from_bgr_stream(width, height, stream)
  string = ChunkyPNG::EXTRA_BYTE # 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 }
  self.new(width, height, pixels)
end
from_rgb_stream(width, height, stream) click to toggle source

Creates a canvas by reading pixels from an RGB formatted stream with a provided with and height.

Every pixel should be represented by 3 bytes in the stream, in the correct RGB order. This format closely resembles the internal representation of a canvas object, so this kind of stream can be read extremely quickly.

@param [Integer] width The width of the new canvas. @param [Integer] height The height of the new canvas. @param [#read, String] stream The stream to read the pixel data from. @return [ChunkyPNG::Canvas] The newly constructed canvas instance.

# File lib/chunky_png/canvas/stream_importing.rb, line 18
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 }
  self.new(width, height, pixels)
end
from_rgba_stream(width, height, stream) click to toggle source

Creates a canvas by reading pixels from an RGBA formatted stream with a provided with and height.

Every pixel should be represented by 4 bytes in the stream, in the correct RGBA order. This format is exactly like the internal representation of a canvas object, so this kind of stream can be read extremely quickly.

@param [Integer] width The width of the new canvas. @param [Integer] height The height of the new canvas. @param [#read, String] stream The stream to read the pixel data from. @return [ChunkyPNG::Canvas] The newly constructed canvas instance.

# File lib/chunky_png/canvas/stream_importing.rb, line 37
def from_rgba_stream(width, height, stream)
  string = stream.respond_to?(:read) ? stream.read(4 * width * height) : stream.to_s[0, 4 * width * height]
  self.new(width, height, string.unpack("N*"))
end