Closed annulen closed 10 years ago
For ARGB444 use --posterize=4
. For RGB565 --posterize=3
will work, but leave one bit of green unused.
Cool! Looks like this option is undocumented.
However, it would be great if pngquant could generate non-indexed images for sake of improved quality. I have an image [1] with color gradients and I'm wondering how much quality can I get from it in ARGB4444. [2] is what I get with Gimp-based solution, and I'm sure that's not the best possible conversion.
[1] http://higgs.rghost.ru/57363540/image.png [2] http://higgs.rghost.ru/57363557/image.png
The option is in the readme and the manpage. I've updated the built-in help. 554add4dbf1568ac768edcf60a6e4fe6bcdbc989
In this particular case I'm afraid you won't see improvement with pngquant, because after posterization that image has only 145 colors anyway, so there's nothing to improve in the quantization step.
Use cases:
Right now I use Gimp script based on [1], adapted to batch processing of images, to quantize them into ARGB444 color space, than I use pngquant if I need to make them indexed (or simply reduce size further). However, [1] uses Floyd-Steinberg and you claim it is not the best dithering algorithm. It's also hard to set up on server (requires whole Gimp + custom script + custom palettes).
[1] http://registry.gimp.org/node/25275