Original http://gridth.s3.amazonaws.com/test-firefox.png
Quantized http://gridth.s3.amazonaws.com/test-firefox-nq8.png
The result file size is impressive, but the image quality is noticeably worse. I'm not sure if I want to use color quantization with PNG though. After all, if I want a lossy compression, I'd use JPEG.
This is exactly what I don't understand about the existence of this program. I don't know much about compression algorithms, but this is definitely lossy compression. I don't know why somebody would want to use it on their lossless PNGs when JPG already exists.
PNG8 allows you to use alpha in palettized form. Images you want to use in a "composite" context(icons, buttons, sprites, etc.) really need alpha to look great, but you don't usually need the full color gamut for them either.
You want to use it when you don’t want any ugly JPG compression artifacts to show up. PNG and JPG produce different compression artifacts, depending on what you are compressing either one could look better.
Only place it's noticeable is the header of the page. I wonder if it's the only place where it save bits, or if it saves some in the rest too. If it does, that seems like the kind of graphic you'd want to use it with.
I think it's a fantastic result. Very useful for including screenshots in blog posts without sacrificing too much quality, but clearly decreasing size.
This is a great tool, I used it to palettize spritesheets for my last game. Caveat: it sometimes palettized the 0-alpha values to 1, resulting in a very faint box around affected images.
Tested with:
Results: Samples: The result file size is impressive, but the image quality is noticeably worse. I'm not sure if I want to use color quantization with PNG though. After all, if I want a lossy compression, I'd use JPEG.