Simple Photo Collage Generation

Last week I implemented support for generating very simple (grid only) collages from photos/images in my image processing infrastructure.

I had wanted to create some simple grid-based collages of some photos, and I was somewhat surprised to discover that neither Krita nor GIMP (free/open source image manipulation software) seem to provide any built-in functionality to generate this type of output, without manually setting up grids/guides and resizing and positioning each image separately - which while not difficult in theory - is somewhat onerous, especially when you want to generate multiple similar collages from different sets of input images in a procedural/repeatable way.

I did briefly look into (free) web-based solutions, however I wasn’t really happy with that avenue either, partly due to most web solutions having the same lack of procedural/recipe generation (i.e. being able to just change the input images and get the same type of result without re-doing things from scratch again), but also because many web solutions seemed more targeted at “artistic” collages with photos having arbitrary positions and rotations, rather than having grid presets, as well as the fact that many (although not all) of the web apps in question required some form of registration or sign-in.

So I ended up just quickly implementing basic support for this collage generation myself in my image processing infrastructure, which took less than two hours, and means I can now generate arbitrary grid collages from a ‘recipe’ source parameters file which configures the target output resolution, the row and column counts, input images list, inner and outer border widths and border colour, as well as the image resize sampling algorithm/filter to use (i.e. bilinear, bicubic, Lanczos, etc) for resizing the input images to fit into the collage grid.