Ben G

I am trying to convert the white color (255 255 255) from jit.lcd matrix into 100% transparent, and then merge it with another matrix from jit.qt.movie via jit.alphabrend. All colors other than white in jit.lcd will be overlaid under the jit.qt.movie matrix.

Can't use jit.rgb2luma because i still need to keep all other colors. Any advice will be appreciated.

Hello,
I am trying to convert the white color (255 255 255) from jit.lcd matrix into 100% transparent, and then merge it with another matrix from jit.qt.movie via jit.alphabrend. All colors other than white in jit.lcd will be overlaid under the jit.qt.movie matrix.

Can't use jit.rgb2luma because i still need to keep all other colors. Any advice will be appreciated.


change-white-into-transparent-in-jit-matrix

You do want jit.rgb2luma so that you can convert your picture to a 1-plane matrix in which some pixels are white and others are not, then you want to use jit.op to make a binary (yes or no) determination of which are white and which are not. THAT matrix will then be your alpha channel (plane 0) which you can repack with the RGB data (the other three planes 1, 2, and 3) of the original image.

You can certainly use Christopher's approach - if I'm understanding the question properly you've basically described a luma key. See jit.lumakey or co.lumakey.jxs if you want to do this via jit.gl.slab.

You can certainly use Christopher's approach -  if I'm understanding the question properly you've basically described a luma key.  See jit.lumakey or co.lumakey.jxs if you want to do this via jit.gl.slab.


Jesse's quite right. Using jit.lumakey is more compact. (Use jit.chromakey for colors other than black or white.)

Thank you Christopher and Jesse for your valuable tips. Also appreciate Christopher's sample patches so I can clearly understand how those functions exactly work.

On the other hand, I was trying to use jit.gl.sketch, jit.gl.videoplane, and jit.gl.render to do something similar, but so far no luck. Also my Max6 crashes very easily when I was messing around these jit.gl.* functions. I read related tutorials but still have lots of question marks on my head.

Change white into transparent in jit.matrix