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Imagemagick is not compressing images like GIMP

Aug 23, 2014, 04:37
Post: #1
Imagemagick is not compressing images like GIMP
How would I replicate GIMPS's default PNG export options with Imagemagick?
I'm using mogrify:
mogrify -define "png:compression-level=9" -format png *.GIF

When I compare the images converted with GIMP to the one converted with Imagemagick the GIMP converted ones are always smaller in file size
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Aug 23, 2014, 08:23 (This post was last modified: Aug 23, 2014 08:38 by rich2005.)
Post: #2
RE: Imagemagick is not compressing images like GIMP
(Aug 23, 2014 04:37)rublacava Wrote:  When I compare the images converted with GIMP to the one converted with Imagemagick the GIMP converted ones are always smaller in file size
Strange, it is usually the other way round.

For a small number of colours, IM will create an indexed png unless the colors level is set higher.

Something like this is closer to a Gimp png with my test image, but not what you want
mogrify -format png -define png:color-type=2 -depth 24 *.gif
where: type 2 = RGB : type 3 = indexed : type 6 = RGBA


for smaller, try simple, as a starting point.
Code:
mogrify -format png -define png:color-type=3 *.gif

mogrify is a very dangerous command, so I hope you have backup files.
The syntax for IM has changed a bit for compression and my notes are out of date.
Best ask the question on th IM users forum.

edit: If you have lots of files to process and want to use Gimp, try the BIMP batch plugin.

** https://www.gimp-forum.net/ now answering questions**
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