Legacy ImageMagick Discussions Archive

"-depth 8" has no effect in this case
"- type truecolor" is the key to solve the problem

O.k. thank you two guys for your amazingly quick replies to my questions + finding the solution for my problem.

So my conclusion is that ImageMagick currently tries to store output into a rare (but probably valid) format (16bit/total) which causes all the trouble.
I would appreciate if ImageMagick ...

$ exiftool testit-orig.tif | grep "Bits Per Sample"
Bits Per Sample : 8 8 8
$ exiftool testit-new.tif | grep "Bits Per Sample"
Bits Per Sample : 16
$ exiftool testit-new2.tif | grep "Bits Per Sample"
Bits Per Sample : 8

Converting with "-posterize 8" color-depth will be kept at 8bit w/o additional parameters.
Converting with "-posterize 64" color-depth will be kept only at 8bit when additionally issuing "-depth 8" and "-type truecolor".

So IMHO behavior for TIFF-conversion currently is inconsistent, isn't it ...

Cool, indeed this works for me as well - seems this could be a workaround for the problem for now.

But still the question is:
Why is it necessary to add all these options to keep color-depth at 8bits for TIFF-conversion using "-posterize"?
I currently would expect to get same result without the ...

If you are getting 16-bits on Q16 and it would fit into 8-bits per channel pixel, then just add -depth 8 to your command.
As already mentioned above - this currently does _not_ work for TIFF-files for whatever reason!

Note that proper IM syntax reads the input right after convert and not at the ...

Starting point is a sRGB-image with "only" 8bits, which is (2⁸)³=256³=16,7Mio colors.
For my understanding option "-posterize 64" should reduce colors to a maximum of 64³ = 262.1444 defined color levels.

But for some reason I don't understand "convert" does increase color-depth to 16bit.
This means ...

Hi there,

on my computer I'm running Fedora FC27, ImageMagick version is
$ rpm -qa | grep ImageMagick
ImageMagick-6.9.9.27-1.fc27.x86_64
ImageMagick-libs-6.9.9.27-1.fc27.x86_64


I'm using a BASH-script which does the following:
1) scanning into TIFF-file(s) (SANE's scanimage)
2) create multipage ...