The ditherImage function has no effect

[Luke-Tang]

import 'package:image/image.dart' as img;

void main() async {
  final cmd = img.Command()
    ..decodePngFile('test_origin.png')
    ..ditherImage()
    ..writeToFile('test_image_dithered.png');
  await cmd.executeThread();
}

origin image

converted image

The two pictures look similar, but the converted image is smaller.
The expected picture should look something like this:

[brendan-duncan]

I'll look into it.

[brendan-duncan]

Wow, I don't know how that function ever worked. What was I thinking?
I'll have to re-work that function.

[brendan-duncan]

I pushed some fixes to git. It's nowhere near as extreme as your final example.

[Luke-Tang]

I appreciate your quick response.

The ditherImage function uses the floydSteinberg algorithm by default.
I tried to use this image to test the new code：

But the resulting picture looks like this：

The example picture in Floyd-Steinberg_dithering's Wikipedia looks like this:

Wikipedia for the Floyd-Steinberg dithering algorithm

[brendan-duncan]

That's not a 1:1 comparison. They converted the image to 2-bit black-and-white. I tested doing that and you see the dither pattern.

[brendan-duncan]

I'll still be working on improving the quantization and dithering results, by the way. Might take a bit, working on lots of projects.

[zhponng]

I have the same situation. The dithered image is not much different from the original image, and the algorithm takes a long time. I look forward to updating it.