davehouse

I'm brand new to Jitter and relatively new to Max so apologies if my question is an obvious one. I've been scouring the forums and help files and not getting anywhere, though. I'm using Max 6 on Windows 7.

Basically what I have is a webcam trained on a white background with the video divided into 6x6 smaller matrixes using jit.scissors. The white background will have coloured powder poured on it over time and I want to track the amount of each colour in each matrix and use the colour values to do audio stuff in MSP. Eg, the higher the red value in Matrix 1, the higher the volume (crude example but hopefully you get the idea).

I've been experimenting with jit.3m which is successfully outputting each matrix' RGB values when colour is added. So far so good. However, since white is R255 G255 B255 it means that my 3 values are constantly maxed out - not much good if I want to track changes in RGB starting from zero (ie, no colours). Using a black background isn't working as the contrast between the colours and the background isn't sharp enough (even when I use BRCOSR).

Is there a way to ignore the white and just concentrate on colour data, or another cunning way around the problem that will invert the data, perhaps? I tried inverting the RGB data with a Scale object but that just presents the same problem in reverse. Ideally I'd like a fully white matrix to essentially give 0 RGB readings which then go up as colour is added.

Basically what I have is a webcam trained on a white background with the video divided into 6x6 smaller matrixes using jit.scissors. The white background will have coloured powder poured on it over time and I want to track the amount of each colour in each matrix and use the colour values to do audio stuff in MSP. Eg, the higher the red value in Matrix 1, the higher the volume (crude example but hopefully you get the idea). 

ignoring-white-when-getting-rgb-values-from-webcam

You could use jit.chromakey to remove white from the matrix and ignore other colors

Thanks for the suggestion, I'll give it a try

As Wesley mentioned, jit.chromakey is a good way to go. However since you're new to Jitter, here's another way using [jit.op] that may help you understand how to do this stuff manually.

Ignoring white when getting RGB values from webcam