Imagemagick Batch Processing

Imagemagick provides powerful tools for image manipulation. These can be easily automated in small shell scripts or command lines.

Shellscript batch processing

The following examples use basename $file to not overwrite the original file. Replace it by $file to overwrite the original.

Scale a bunch of photos

This scales all .JPG files in the directory ../mypics to 2048x1536 pixels. Note that the file extension (.JPG) is case sensitive and will not match .jpg files. The aspect ratio is preserved.

for file in ../mypics/*.JPG; do echo $file; convert "$file" -scale 2048x1536 -quality 85 `basename "$file"`; done

Crop out a section of PNG files

This cuts out the upper left 6x17 pixels. +0+0 adjusts the offset. Use -depth 8 to get 8bit PNGs instead of 16bit.

for file in ../my_pngs/*.png; do echo $file; convert $file -crop 6x17+0+0! -depth 8 `basename $file`; done

... can of course be combined with -scale, here with different parameters:

for file in ../my_pngs/*.png; do echo $file; convert $file -crop 90x45+0+13 -scale 72x36! -depth 8 `basename $file`; done