Is it possible to improve the pngquant output in this case?

Question

Here is part of the original image

Here is the output from pnqguant with quality set to 50.

You can see the artefacts in the shadow area of the compressed image is very prominent.

Is there any pngquant parameters I can tweak to improve the visual quality

Answer 1

Here are tips that helped me resolve the same exact issue:

1. Make sure you use version 2 of pngquant, on their website they have good comparisons of version 2 vs photoshop 'Save for web' feature. Shadows are perfect there.
2. Make sure you use --speed parameter (I've found that setting it to slowest value 1 gave me the most perfect shadow), and by default they don't use the slowest option.
3. Make sure you play with all possible values --quality, finding the most optimal tradeoff between shadow quality and image size.