For the lecture Machine Mediated Vision I created my first patch in Quartz Composer. The patch shows a minute-long clip from the movie “The Big Lebowski” on the right, and the average motion in grayscale on the left. The patch queues the images and compares the actual image to another one earlier in the clip which can be specified with an index. Then a difference blend filter is applied combined with a small custom core image filter and the area average filter to get the grayscale value. The output here was only 1x1 pixels and for some reason “Image Pixel” couldn’t be applied here, so I had to transform the image and scale it up a bit to extract one pixel and get the RGBA values from it. These are multiplied by 10 and then displayed in the sprite.
You can download AverageMotion here (25 MB).
AverageMotion by Patrick Heneise is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.