Imagemagick recursively reduce files to < 800x600 and 72ppi

bulk-resize-script

# This is a bash script meant to be run on the command line. Requires imagemagick (apt-get install imagemagick)
## THIS WILL OVERWRITE YOUR FILES, uses sudo and may not require it.
for file in /path/to/files/*/*.jpg; do sudo convert $file -resize '800x600>' -density 72 $file; done

### another method using resolution (800*600)
for file in /path/to/files/*/*.jpg; do sudo convert $file -resize '480000@>' -density 72 $file; done

### example of *not* overwriting files
for file in /path/to/files/*/*.jpg; do sudo convert $file -resize '800x600>' -density 72 converted-$file; done

ty

thank you.
I had to improve it if you have spaces in filename (sometimes users do things like that...)
also add quality param

for file in /path/to/files//.jpg; do sudo convert "$file" -resize '800x600>' -density 72 -quality 85 "$file"; done

how to change resolution by biggest size for example maximum width 1000 px ?

@Fayozjon you would use the image geometry properties to specify the width only.
convert $file -resize '1000'
I don't think you can specify the > to resize only images larger than the specified dimensions, so be careful with this.

Ready more about Image Geometry.