I see that the GIMP manual states: " his “PNG8” format, like GIF, uses only one bit for transparency only two transparency levels are possible, transparent or opaque. Note also that IrfanView does an awful job of converting 32-bit PNG images to 256, allowing only one transparent color, which looks bad if full color was dithered! Note on IrfanView support: if it handles PNG8 correctly for transparency, it doesn't handle gamma information in PNG files: on the toucan image or the ping-pong image, I had to apply a gamma of 2.4 to get similar (lighter) colors. It might be an interesting complementary tool for this format. Even more, it allows to edit each palette entry, color and alpha level. The dithering algorithms (the two of pngquant, the only one of pngnq) are different, and it might be worth having both tools, converting images with all algorithms and see what looks the best.įor the record, on the Windows side, IrfanView (4.10) displays these images very well (using the transparency level on each palette entry) while XnView (1.85.1) and GIMP (2.4) apply only a full transparency/opaque display, à la GIF: the light bulb given as an example in the linked article has a transparent background around it, but the orange part is fully opaque.Īnd the excellent utility TweakPNG shows we have a PLTE (palette, 222 entries) chunk and a tRNS (alpha values for palette colors, 222 entries) chunk. The latter seems to do a slightly better job on the IceAlpha.png test image (from ), at the cost of a slightly bigger image (it can be post-processed with pngcrush or pngout anyway). Ah, if I remember correctly, when I have read this article some months ago, pngquant hadn't a Windows version.
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