contrast function

Image? contrast(Image? src, num contrast)

Set the contrast level for the image src.

contrast values below 100 will decrees the contrast of the image, and values above 100 will increase the contrast. A contrast of of 100 will have no affect.

Implementation

Image? contrast(Image? src, num contrast) {
  if (src == null || contrast == 100.0) {
    return src;
  }

  if (contrast != _lastContrast) {
    _lastContrast = contrast;

    contrast = contrast / 100.0;
    contrast = contrast * contrast;
    _contrast = Uint8List(256);
    for (var i = 0; i < 256; ++i) {
      _contrast[i] =
          clamp255((((((i / 255.0) - 0.5) * contrast) + 0.5) * 255.0).toInt());
    }
  }

  final p = src.getBytes();
  for (var i = 0, len = p.length; i < len; i += 4) {
    p[i] = _contrast[p[i]];
    p[i + 1] = _contrast[p[i + 1]];
    p[i + 2] = _contrast[p[i + 2]];
  }

  return src;
}