Legacy ImageMagick Discussions Archive

IM 6.6.2-4 Q16 Mac OSX Tiger

I have written a new script that appears to be having problems disabling dithering. Rather than repeat the script, I have simplified an example to show this.

If I start with JPG or PNG with lots of colors and end with a gif, then I get dithering even with +dither in command line. This does not happen if I start with 256 color or less GIF.

Here are the test input images:

JPG

PNG
http://www.fmwconcepts.com/misc_tests/d ... radise.png
GIF
http://www.fmwconcepts.com/misc_tests/d ... radise.gif

Processing:

JPG:
convert birdofparadise.jpg -sample 5% -scale 2000% +dither birdofparadise_pixelize_jpg.gif


Notice above that several squares on the left side show a speckling that I presume is due to dither. Other squares show similar speckling if the image is made brighter


PNG:
convert birdofparadise.png -sample 5% -scale 2000% +dither birdofparadise_pixelize_png.gif
http://www.fmwconcepts.com/misc_tests/d ... ze_jpg.gif

GIF:
convert birdofparadise.gif -sample 5% -scale 2000% +dither birdofparadise_pixelize_gif.gif
http://www.fmwconcepts.com/misc_tests/d ... ze_gif.gif

Look for a patch to the problem you reported in ImageMagick 6.6.2-5 Beta in about an hour. Thanks.

Thanks. The beta seems to have fixed the bug. My test case has no speckle and my script does not produce any speckle either.

Fred