[jschwartzi]

you might get better results with a run-length encoding on a dithered image. I’m not aware of any modern image formats that use RLE though.

[vanderZwan]

I've experimented with that. It only works if you pick you pick a form of ordered dithering, like a Bayer index or Interleaved Gradient Noise[0][1]. Which looks pretty terrible compared to error diffusion dithering approaches like Sierra3. And even if you use ordered dithering it only somewhat helps with compression.

[0]https://bartwronski.com/2016/10/30/dithering-part-three-real...

[1] https://www.iryoku.com/next-generation-post-processing-in-ca...

[janekm]

A dithered image tends to produce very short runs of pixels so is likely to get poor compression with RLE.

Ordered dithering with a compression algorithm that can compress "words" (repeated patterns) (like the LZW in GIF) will perform better if the image has large areas of flat colour (not photos).

[klodolph]

PNG uses deflate, which can encode runs of repeating values very efficiently. A run of repeating XYZXYZX… will get encoded as

Literal X, literal Y, literal Z, copy distance=3 length=N

[StillBored]

Was going to say, this but tiny correction, its the LZ variant that does this, as will most of them. Deflate is just two pass compression of LZSS followed by Huffman. The LZ variant will pick out repeat patterns, while the second will compress the byte representation of the resulting stream if a particular set of values is over represented. AKA its all variations of X, Y, Z in different orders those might get assigned 2 bit values rather than the 8 they normally might take up.

(so this a bit of a rant I have about people calling deflate a compression algorithm, its an algorithm composed of two other fundamental ones).

[asxd]

Maybe just encode it as a bitmap, and then use other types of compression like RLE. Dithering reduces the color palette, so in combination with a bitmap it would reduce the memory footprint of each pixel.

[ska]

The opposite is likely. RLE works best with long "runs" of the same value. Dithering will tend to break up these regions if it improves quantization error.

[coding123]

PCX was RLE. I remember playing with PCX files in C++ back in the day.