OK, here is a possible implementation, one can play with several channels at once, too.
I animated the effect, for added fun...
- void setup()
- {
- size(650, 650);
- // Image found at http://www.parc-causses-du-quercy.org/index.php/photos/paysage_typique_causse
- PImage image = loadImage("G:/Images/References/paysage_typique_causse.jpg");
- image(image, (width - image.width) / 2, (height - image.height) / 2);
- xRtoL = width - 1;
- yBtoT = height - 1;
- }
-
- int xLtoR, xRtoL, yTtoB, yBtoT;
- void draw()
- {
- loadPixels();
- for (int i = 0; i < height; i++)
- {
- int pos = i * width + xLtoR;
- pixels[pos] = mapColor(pixels[pos], B, xLtoR, width / 2);
- pos = i * width + xRtoL;
- pixels[pos] = mapColor(pixels[pos], G, width - 1 - xRtoL, width / 2);
- }
- xLtoR++;
- xRtoL--;
- for (int i = 0; i < width; i++)
- {
- int pos = yTtoB * width + i;
- pixels[pos] = mapColor(pixels[pos], R, yTtoB, height / 2);
- pos = yBtoT * width + i;
- pixels[pos] = mapColor(pixels[pos], R, height - 1 - yBtoT, height / 2);
- }
- yTtoB++;
- yBtoT--;
- updatePixels();
- if (xRtoL < width / 2 || yBtoT < height / 2)
- {
- noLoop();
- println("Done");
- }
- }
-
- int mapColor(color clr, int channel, int cur, int max)
- {
- int chan = 0;
- switch (channel)
- {
- case R: // Red
- chan = (clr & 0x00FF0000) >> 16;
- clr &= 0xFF00FFFF;
- break;
- case G: // Green
- chan = (clr & 0x0000FF00) >> 8;
- clr &= 0xFFFF00FF;
- break;
- case B: // Blue
- chan = clr & 0x000000FF;
- clr &= 0xFFFFFF00;
- break;
- }
- chan = int(1.0 * chan * cur / max) & 0xFF;
- switch (channel)
- {
- case R: // Red
- clr |= chan << 16;
- break;
- case G: // Green
- clr |= chan << 8;
- break;
- case B: // Blue
- clr |= chan;
- break;
- }
- return clr;
- }
