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Old 03-22-2011, 08:53 AM   #33
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glennrp began at the beginning.
Posts: 3
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Join Date: Mar 2011
Device: kindle
Originally Posted by Honf View Post
Setting the color pallet to 16 make the images look very bad (they open just fine in windows image viewer). Seems like the Kindle has a slight problem with its png decompresser.
Yeah, if you simply used
pngcrush -plte_len 16 ...
it could generate an invalid PNG. That dangerous option is only for truncating a palette with unused entries at the top. To actually quantize your image down to 16 colors with pngcrush you also need to set the bit-depth to 4, i.e.,
pngcrush -bit_depth 4 -plte_len 16 ..
which simply drops the low 4 bits of each color sample, or you could use another application like ImageMagick or pngquant to get a better-looking quantization. I'll look into making pngcrush give a better error return if valid palette entries are being truncated with the -plte_len option. ../glennrp
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