If you use Google to ask this question the first hit is actually the pngnq website, which explicitly states that pngnq is a modification of pngquant, and supposedly an improvement.
> Pngnq is an adaptation by Stuart Coyle of Greg Roelf's pnqquant using Anthony Dekker's neuquant algorithm.
> Why another quantizer?
> Pngnq exists because I needed a lot (several thousand) of png images in RGBA format to be quantized. After some searching, the only tool I could find that worked for RGBA was pngquant. I tried pngquant but found that the median cut algorithm that it uses, with or without dithering, gave inferior looking results to the neuquant algorithm. You can see the difference demonstrated on the neuquant page.
I compared them recently for a project where I needed to make some PNGs smaller, and settled on pngng, which, in my informal testing, seemed to produce better results.
Yes. 1.0 was written in the MS-DOS era, truncates quality to 15-bits, has buggy alpha and uses basic Median Cut algorithm from early 80s.
2.0 is by now a totally different program, with expanded and improved algorithms (with bits of machine learning) and uses 128 bits per pixel precision (SIMD+multicore optimized).
http://pngnq.sourceforge.net
> Pngnq is an adaptation by Stuart Coyle of Greg Roelf's pnqquant using Anthony Dekker's neuquant algorithm.
> Why another quantizer?
> Pngnq exists because I needed a lot (several thousand) of png images in RGBA format to be quantized. After some searching, the only tool I could find that worked for RGBA was pngquant. I tried pngquant but found that the median cut algorithm that it uses, with or without dithering, gave inferior looking results to the neuquant algorithm. You can see the difference demonstrated on the neuquant page.