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Old 10-16-2013, 11:30 AM   #27
Jellby
frumious Bandersnatch
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Join Date: Jan 2008
Location: Spaniard in Sweden
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Quote:
Originally Posted by SBT View Post
I use imagemagick (convert in.jpg -colorspace gray -colors 16 out.png), and then use pngcrush, but without specifying bit depth.
Depends on what imagemagick is actually doing. I'd say that "-colors 16" just reduces the number of colors, but does not constrain each of these colors to be 4-bit representable. If that is the case, pngcrush will not reduce the bit depth either.

In short: 4 bits implies 16 gray levels, but 16 gray levels does not imply 4 bits.
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