how to make a pixel transparent?

edited March 2017 in How To...

I seem to recall there was already a topic on this but I can't find it ... so what I want to do is loop through an array of pixels and make all the pixels above a certain brightness value transparent. How would I do this? Thanks!


  • edited March 2017 Answer ✓
    // GoToLoop (2017-Mar-28)
    PImage makeTooBrightColorTransparent(final PImage img, final int bright) {
      final color colors[] = img.pixels, len = colors.length;
      for (int i = 0; i < len; ++i) {
        final color c = colors[i];
        if (brightness(c) >= bright)  colors[i] = c & ~PImage.ALPHA_MASK;
      return img;
  • Thanks! It seems to work, but not perfectly, on a video too ... most of the time it works but at times some of the bright pixels are not being turned transparent ... weird ...

  • edited March 2017

    You haven't said anything about video! [-(
    If method read() is called under another Thread, its pixels[] is completely filled by the new arrived frame! :-@

  • Ah ok ... sorry :/

    Uh, so my code look like this right now:

    void draw() {      
    if (movie.available()) {   
            image(makeTooBrightColorTransparent(movie, 100), 0, 0);
  • Seems correct. Method read() is called under the "Animation" Thread.
    So it should just work. Dunno why it fails sometimes for ya according to what you've posted so far.

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