View source for Imagemagick Batch Processing

[http://www.imagemagick.org Imagemagick] provides powerful tools for image manipulation. These can be easily automated in small shell scripts or command lines.

=Shellscript batch processing=
Some of 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.
 <nowiki>for file in ../mypics/*.JPG; do echo $file; convert "$file" -scale 2048x1536 -quality 85 `basename "$file"`; done</nowiki>

==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.
 <nowiki>for file in ../my_pngs/*.png; do echo $file; convert $file -crop 6x17+0+0! -depth 8 `basename $file`; done</nowiki>
... can of course be combined with '''-scale''', here with different parameters. '''!''' ignores the aspect ratio and ensures that the output images have the exact resolution given:
 <nowiki>for file in ../my_pngs/*.png; do echo $file; convert $file -crop 90x45+0+13 -scale 72x36! -depth 8 `basename $file`; done</nowiki>

==Fade in/out==
A fade in and out effect for PNG sequences, easily done with '''-modulate''':
 <nowiki># Fade in, 60 frames:
i=0; for file in ../my_pngs/*.png; do echo $file; convert $file -modulate $(( ( $i * 100 ) / 60 )) -depth 8 $file; i=$(($i + 1)); done

#Fade out, 60 frames:
i=60; for file in ../my_pngs/*.png; do echo $file; convert $file -modulate $(( ( $i * 100 ) / 60 )) -depth 8 $file; i=$(($i - 1)); done</nowiki>
'''Attention:''' These two examples overwrite the original files.

==Process multiple directories==
Applying the same procedure to images in all subdirectories of the current path:
 <nowiki>for dir in `find -type d`; do for file in $dir/*.png; do echo $file; convert $file -crop 24x48+12+0! -depth 8 $file; done; done</nowiki>
'''Attention:''' Overwrites the original files.

=What else?=
* '''convert -rotate 90''' Rotates the image 90 degrees (or any multiple of 90 degrees)
* '''composite -compose''' Add multiple images, also with transparency

Imagemagick convert can do much more image conversions. For example blurring, various resize methods and colour filters or even blending images. See the [http://www.imagemagick.org/script/command-line-options.php Command-line options] for details.