// Must install ImageMagick first
http://www.imagemagick.org/script/index.php
//This compresses a jpg with no visible loss of quality. Add in your own file names for target.jpg and result.jpg
convert -strip -interlace Plane -sampling-factor 4:2:0 -quality 85% target.jpg result.jpg
// This does the same as above but to an entire folder (will overwrite original files):
mogrify -strip -interlace Plane -sampling-factor 4:2:0 -quality 85% *.jpg
//This does the same thing but to all subfolders as well (Be careful with this one it will overwrite all original files)
//This one just tests the command and prints output
find . -name "*.jpg" -exec echo
mogrify -strip -interlace Plane -sampling-factor 4:2:0 -quality 85% {} \;
// This one actually compresses all the images in folder and subfolders
(the real thing)
find . -name "*.jpg" -exec mogrify -strip -interlace Plane -sampling-factor 4:2:0 -quality 85% {} \;
// This command compresses a png with no visible loss of quality
mogrify -filter Triangle -define filter:support=2 -unsharp 0.25x0.08+8.3+0.045 -dither None -posterize 136 -quality 82 -define png:compression-filter=5 -define png:compression-level=9 -define png:compression-strategy=1 -define png:exclude-chunk=all -interlace none -colorspace sRGB *.png
These commands were copied or adapted from the following sources:
http://www.imagemagick.org/discourse-server/viewtopic.php?t=24134
http://stackoverflow.com/questions/27267073/imagemagick-lossless-max-compression-for-png
https://sangpo.wordpress.com/2009/01/24/recursive-batch-image-resizing-in-linux/
http://stackoverflow.com/questions/7261855/recommendation-for-compressing-jpg-files-with-imagemagick