Releasing Colab Mosaic Clip — a Google Colab tool for applying mosaics to any region of a video
Today I'm releasing Colab Mosaic Clip — an open-source tool that applies a mosaic or solid-color mask to any time range and region of a video, entirely through a GUI, and exports the result as MP4. It runs ffmpeg and Pillow on Google Colab, so everything from specifying the time range to placing mosaic regions and exporting the final file is handled inside the notebook UI.
Background
When sharing screen recordings of tools I've built or internal documentation, I repeatedly run into the same situation: API keys or account information are visible in the footage, so I can't publish it as-is.
The immediate trigger was my own repeated experience using a tool I previously released for converting demo videos to GIF and MP4 — I kept wishing mosaic processing were part of the same workflow. Adding the feature to the existing tool would have complicated the codebase, so I decided to build it as a dedicated, separate tool. Since I wanted to avoid installing video editing software locally — both to keep my environment clean and to avoid a learning curve — I kept everything running in Google Colab, just as before.
Key Features
The tool is designed to run without writing any code. Just execute the cells from top to bottom and handle everything through the video player and Canvas-based GUI.
While playing the video, pressing the "Record Start" and "Record End" buttons is all it takes to set the time range for the mosaic. The frame at the start time is automatically displayed, so you can immediately click on the Canvas to place mosaic regions. Regions can be moved and resized by dragging, and multiple regions can be specified at once.
Two masking patterns are available: pixelated mosaic and solid-color fill. The output width can be set anywhere from 240 to 1920 px. After export, you can preview the result directly in the notebook, then choose to download it locally or save it to Google Drive.
For technical implementation details — including Canvas UI coordinate scaling, the FFmpeg filter_complex overlay approach, and Pillow-based preview processing — see the technical documentation.
Getting Started
No setup required. Open the Colab link below and run the cells from top to bottom.
- Run on Google Colab: Colab Mosaic Clip (English)
- View the source code: hiroaki-com/colab-mosaic-clip on GitHub
Feedback and pull requests are both very welcome.