Reduce color depth and dither?

[NimaiMalle]

I tried all of the following, but the resulting image has color bands - no dithering.

Code: Select all

convert Sample.png -depth 4 Sample2.png 
convert Sample.png -depth 4 -dither FloydSteinberg Sample2.png 
convert Sample.png -depth 4 +dither Sample2.png 

=>

Any suggestions appreciated!

[snibgo]

convert Sample.png -colors 16 Sample2.png

[NimaiMalle]

convert Sample.png -colors 16 Sample2.png

Thanks for the reply. A 16 color pallet is different than a color depth of 4, 16-bit RGBA.
Still looking for way to get that to dither...

[snibgo]

Ah, sorry. "-remap" can dither, and can use the colours from your Sample2:

Code: Select all

convert Sample.png -depth 4 Sample2.png 
convert Sample.png -remap Sample2.png Sample3.png

Is Sample3.png what you want?

[NimaiMalle]

Fascinating. There are some peculiar artifacts but it did indeed dither.

[anthony]

See IM examples
http://www.imagemagick.org/Usage/quantize/