Legacy ImageMagick Discussions Archive

Convert is adding some green pixels to the grey sphere gif file.
Any ideas how to correct this?

This is the command I ran:
C:\Program Files\ImageMagick-6.3.4-Q16\convert
-trim
-density 1200
-profile E:\graphics\bin\USWebCoatedSWOP.icc
C:\bi111222p_f12.eps
-profile E:\graphics\bin\AdobeRGB1998.icc
-resize "950x525>"
-filter Lanczos
-quality 90%
C:\bi111222p_f12.gif

These are the input and output files:
http://www.myfamilyregister.com/photos/ ... 2p_f12.eps
http://www.myfamilyregister.com/photos/ ... 2p_f12.gif

Thanks,
Jim

That would probably be cause by the limitation of the GIF color table.
It is colorful image, and GIF only allows 256 colors at the most. To achieve more colors it dithers the color it has decided to use to produce what looks to use as extra colors. The green pixels is where the algorithm breaks down, due to the use of the Error Correction Dither.

See Error Correction Dithers
http://www.imagemagick.org/Usage/quantize/#dither_error

If you wait a day or two you can also look at E-Dither Speckling which I have re-added to IM Examples.
http://www.imagemagick.org/Usage/quanti ... er_speckle

The best solution -- DO NOT USE GIF use PNG or JPEG instead.

The next best soltuion is to try to use an ordered dither, or use a color map designed to work well with this image. Neither of these are particularly easy to apply to a general image at this time. I myself have been researching into improved generalized ordered dithering for a better overall solution, but could use some help.

See http://www.imagemagick.org/Usage/quantize/#od_posterize which highlights my last O-Dither improvements, and http://www.imagemagick.org/Usage/video/#gif for a example of using it to improve and optimize a Video to GIF conversion.