Software for creating PNG 8bit transparent images?

Question

I\'m looking for software to create PNG8 format transparent images as per this article.

NOTE: I need a linux solution myself, but please submit answ

Answer 1

It depends on what exactly your original images look like.

If your images already contain 256 or fewer colors (RGBA values), you need only look at pngout (Windows) (Linux/BSD/Mac OS X ports), which you should already be using to optimize your PNGs anyway. It can't quantize images, but can save them as 8-bit, including alpha transparency. Just pass in the /c3 (or -c3 on Linux et al.) color option to force it to save the image as PNG8.

If your images do contain more than 256 colors, you have a few more, but all less than perfect options:

• Adobe Fireworks is probably the best option in terms of resulting image quality. It will do the job if you only need to convert a few images, or if you don't mind relying on Fireworks to do the batch processing. I did find that it sometimes somehow limits the number of colors in the palette, creating a worse quality image than necessary. I don't know if that's perhaps a bug in CS3 that's been fixed in CS4.

  If you're not on Windows or OS X this obviously isn't an option, and buying Fireworks just for this probably isn't worth it either.

• The only alternatives I know of are the already mentioned pngquant and pngnq. I've had better luck with pngnq, but that's probably just going to depend on which quantization strategy works best on the files you're working with.

  Unfortunately, I've noticed that neither of them work very well with small amounts of transparency (say, an opaque image with transparent, rounded corners).