ImageMagick is an application that allows us to manipulate images through the command line and that is used for practically all formats. With it, it is also possible to automate the actions on the images contained in a folder (conversion, resizing, etc ...)
Let's see a list of useful ImageMagick commands:
Get information from an image.
identify -ping image.png
Get even more information.
identify -verbose image.png
Know the list of colors used in an image.
identify -list color image.png
Convert a PNG image to JPG
convert image.png image.jpg
Convert a PNG image to JPG indicating the conversion quality.
convert -quality 96 image.png image.jpg
Convert all PNG images to JPG contained in a folder
mogrify -format png *.jpg
Convert all images (* .jpg, * .png) to PDF
convert images*.* archivo.pdf
Resize an image
convert -resize 48×48 image.png image-mini.png
Resize all images in a folder
mogrify -resize 48×48 *.png
Resize an image by specifying the width
convert -resize 620x image.png image-620.png
Resize an image by specifying its height
convert -resize x100 image.png image-100.png
Create a Favicon
convert -colors 256 -resize 16×16 image.jpg favicon.ico
Convert a color image to black and white
convert -type image.jpg image-noir-blanc.jpg
Add a 1 pixel transparent border around an image
convert -bordercolor Transparent -border 1×1 image.png image-borde.png
Add a 10 pixel black border around an image
convert -bordercolor #000000 -border 10×10 image.png image-borde.png
Create a negative of an image
convert -negate image.png image-negate.png
Rotate an image vertically
convert -flip image.png image-inversee.png
Rotate an image from left to right
convert -flop image.png image-inversee.png
Use the ImageMagick GUI
display image.png