These are a couple of customer patches I have made for Quartz Composer.
I wrote these because I wanted to solve "How can I easily detect how much movement is there in a section of an image".
This grid does that but having each cell analyse its corresponding section on a source image. How much red is there determines the weight of that cell. This can be used to detect white, which can then be used to detect movement.
This is my first video tutorial as well as my first go at Cocoa, so any feedback would be great.
You can see this and more of my work at my website -> dlangford.net/content/sw-weighted-grid-generator-and-renderer
** Edit: Download them from here to make sure you always get the latest ( code.google.com/p/swquartzcomposerpatches ), They are called [SW] Weighted Grid Generator and [SW] Weighted Grid Render and are in the green box on the right. **
Feel free to do what you want with it just let me know. I want to see what you do!