Hey kids,
  I am working with the OpenCV libraries and I would like to do some finger detection. I looked a bit into Haar features and that might have some potential, but then it occurred to me to wrap a colored paper around my finger then filter out everything except that color and then do some blob detection.

However, my hang up is on the image manipulation. I had a friend do some photoshop magic and he got pretty close with a darken red and green channels (I had a yellow piece of paper on my finger).
So, my questions:
1) How can I "darken" red and green? I have been playing with the PImage.set( x, y, color ) method, with mixed results. Is there a better way to do this?
2) What other image libraries are out there that would give me some similar control that is available in photoshop or gimp?

Here is what I have so far.
Code:

import hypermedia.video.*;

OpenCV opencv;
PImage img;
PImage redImage;
PImage greImage;
PImage bluImage;

PImage test, test2;

void setup() {
  size( 640, 480 );
  opencv = new OpenCV(this);
  opencv.capture(width,height);

  redImage = createMask( width, height, 255, 0, 0 );
  greImage = createMask( width, height, 0, 255, 0 );
  bluImage = createMask( width, height, 0, 0, 255 );

  test = createMask( width, height, 255, 255, 0);
  test2 = createMask( width, height, 0, 0, 255 );

}

void draw() {
  opencv.read();
  //   opencv.threshold( 50 );

  img = opencv.image();

  if( key == 'r' )
    img = myMask( img, 0, -1, -1 );
  else if( key == 'g' )
    img = myMask( img, -1, 0, -1 );
  else if( key == 'b' )
    img = myMask( img, -1, -1, 0 );

  image( img , 0, 0 );
}


PImage myMask( PImage i, int r, int g, int b )
{

  for( int x=0; x<i.width; x++ )
    for( int y=0; y<i.height; y++ ){
      if( r != -1 )
        i.set( x, y, color( r, green( i.get( x, y ) ), blue( i.get( x, y ) ) ) );

      if( g != -1 )
        i.set( x, y, color( red(i.get(x,y)) , g, blue( i.get( x, y ) ) ) );
      if( b != -1 )
        i.set( x, y, color( red(i.get(x,y)) , green( i.get( x, y ) ), b ) );
    }
  return i;  
}

PImage createMask( int w, int h, int r, int g, int b )
{

  PImage img = createImage( w, h, RGB );
  img.loadPixels();
  for (int i = 0; i < img.pixels.length; i++) {
    img.pixels[i] = color(r, g, b );
  }
  img.updatePixels();

  return img;

}