Apr 23 2006 | 11:35 pm
    Is there a way to convert luma to RGB? It seems to be the only colorspace
    conversion combo not offered?
    My webcam feed goes through various processes to arrive at an edge/outline
    simple image. Part of which involves pix.rgb2luma. Can it go back the other
    way post-process so I can colour the outline images?...doesn't have to be
    the original colours.

    • Apr 24 2006 | 1:01 am
      If you think about it, how would this's entirely possible
      that several RGB colors can convert to the same luma value. You're
      mapping a 24bit pixel space to an 8bit pixel space. How would you go
      from 8bit to 24bit? If you have several luma values that are the
      same, do you map them to the same color? If not, then how do you
      choose which value of say 55 luma maps to any particular color?
      You're going to need some more information.
      That said, there are 2 ways I can think of for doing what you want...
      1->Take your edges and get the colors from the source video at the
      same pixel locations. "jit.op @op *" might do this for you
      2->Create your own mapping from luma to RGB space based on your needs
      and use jit.charmap to process the conversion. I have made an object
      that does this if you're curious. It's called xray.jit.colormap
    • Apr 24 2006 | 8:45 am
      'luma' matrices are only 1-plane matrices, where rgb(+alpha) are 4-plane.
      so, just add 4 plane jit.matrix after you're done with luma processing.
      to color this matrix, you could simply multiply this gray 4-plane matrix
      with rgb values, using jit.op @op * @val -alpha intensity- -red
      intensity- -green intensity- -blue intensity-
      an example:
      some stuff
      jit.matrix 4 char 320 240
      | (after this, you have rgb matrixes, where alpha channel is also 'luma')
      | pak 255 255 255 255
      | |
      jit.op @op * @val 255 255 255 255
      or, if you want to leave alpha chanel, you would use @op pass * * *
      realy nice thing about jitter is that matrixes are just data, some people
      store music in it, some text, even code. some people use it for images of
      various flavors, you're not constrained to one particular format, like pix.*
      might be.