pngquant is a batch conversion utility to quantize and dither truecolor PNG images, especially those with a full alpha channel, down to "RGBA-palette" PNGs (i.e., PLTE + tRNS in PNG parlance). Such images are usually two to four times smaller than the full 32-bit versions, and partial transparency is preserved quite nicely. This makes pngquant especially useful both for Web sites and for PlayStation 2 development, where one of the texture formats is RGBA-palette-based (though not PNG-compressed).
Twibright Registrator removes noise and can quadruple the resolution of a camera in software by matching several pictures together. It can be applied to remove noise, JPEG artifacts, rain, CRT stripes, and passersby. It can enhance night photos and provide the effect of long exposure in daylight. Pictures are matched by removing shift, rotation, zoom, and brightness changes. It features high performance bilinear interpolation, automatic adaptive corrective deconvolution, 32-bit float depth, photometrically linear space, and 16-bit depth PNG output.