If you have many photos and wondering which software to use in order to create photo collages under Ubuntu, you can easily use ImageMagick to create photo collages from the Terminal.
First, make sure ImageMagick is already installed on your system. If it is not installed, then run this command from the Terminal:
sudo apt-get install imagemagick
Now cd to the folder containing your photos (photos must have the same extension: .jpg, .png, etc.), then run this command to create a photo collage:
montage *.jpg output.jpg
You can replace jpg with any other image format supported by ImageMagick (PNG, BMP, etc.). The generated image file (output.jpg) will be saved in the current folder. The result will be similar to this:
There are many options you can apply on photos using the montage command line tool. You can find all of them here. Here is an example:
montage *.jpg -border 2x2 -background black +polaroid -resize 65% -geometry -60-60 -tile x6 output.jpg