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Title made we wonder if there was such a think as lossy PNG - apparently yes: http://membled.com/work/apps/lossy_png/ http://membled.com/work/apps/lossy_png/
by ramchip 17y ago
Title made we wonder if there was such a think as lossy PNG - apparently yes: http://membled.com/work/apps/lossy_png/ http://membled.com/work/apps/lossy_png/
- DarkShikari 17y agoAny lossless format can be made lossy by simply performing a lossy pre-pass prior to the lossless compression. The real challenge is finding a good way to perform the pre-pass; it's easy to pick a simple naive method, but optimality is likely exponential-time, or if one is lucky, polynomial with an intractable constant (using trellis). The fact that PNG uses a dictionary-based compressor instead of a PPMD-like system likely makes the problem much harder.