I took a few hundred timelapse pictures of 4th of July fireworks from my rooftop in Highland Park, Los Angeles over the course of three hours. Instead of immediately making a video I decided to experiment with image compositing using RMagick (Ruby bindings to ImageMagick).

Blenderrr is a script that uses RMagick with the Lighten blending operation to batch-process images found in a folder into a single composite image. It has command line options to control how many images are processed, including skipping every N images to reduce the amount of input to the composite.

The main thing to watch out for with Lighten is that the earliest photo will set the tone of the background – since it will always be lighter than the background of later photos. The image below starts around 7:30 PM instead of 8:45PM

It can also make gifs! Both by accumulating each frame, and a more traditional timelapse.