I have a lot of images which have white borders around them. I would like to crop those borders all at once, preferably from command line. I believe that it can be done with ImageMagick, but I couldn't find suitable command.
I know that it can be done with Windows program named Irfanview with "Auto crop borders" option, but I am looking for Ubuntu-based and preferably command line based solution.
The command line option trim used together with convert, or mogrify lets you trim borders of the same color as the corners of an image.
Usage:
convert input.png -trim output.png
The additional option -fuzz (which takes a percentage as an argument, e.g. -fuzz 10%) also removes colors near the corner colors.
Note: The -fuzz option must precede -trim because options' order matters for convert command to work as expected.
Use the option +repage to remove a canvas (if applicable).
Above command for ImageMagick Trim can also be used to batch process images combined with the find command:
find ./ -name "pattern" -exec convert {} -trim outputfolder/{} \;
The above command will trim all images that fit the pattern part of the command and save them in a new folder named outputfolder.
Assuming that images are PNGs, then command will look like this:
find ./ -name "*.png" -exec convert {} -trim outputfolder/{} \;
While find allows for much greater control where output files will be placed, it is also possible to do the same with ImageMagick's mogrify:
mogrify -trim *.png
And if you want to crop colors near the corner colors (adjust the percentage based on the results you are observing):
mogrify -trim -fuzz 10% *.png
Please note that unlike convert and batch operation with find and convert, mogrify overwrites all files. To keep the originals use the -path option or do a backup copy of all images in the directory before proceeding with the mogrify command.
Side note: mogrify can be used to execute most (if not all) convert operations in batch, while overwriting original files.
As Trevor noted in the comments, you can use the -path option to output converted files to a new directory without overwriting the original files:
mogrify -trim -path trimmed_folder/ *.png
IrfanView runs quite nicely with Wine. Be sure to check the output of Irfanview carefully, as it sometimes breaks images when used with Wine.
