Install caja-image-converter by entering the following commands in the terminal:
sudo apt update sudo apt install caja-image-converter
Caja extension to mass resize or rotate images
Caja is the official file manager for the MATE desktop. This package adds extended functionality to the Caja file manager. . This package adds a "Resize Images..." menu item to the context menu of all images. This opens a dialog where you set the desired image size and file name. A click on "Resize" finally resizes the image(s) using ImageMagick's convert tool.