Okay so now that this is all changed around and I'm trying to get the shape of the drawn brush (sort of like a paint brush) to be a medicine wheel (ellipse with four arcs of different hues--red, black, yellow, white), it's now broken. It runs but doesn't do anything when the mouse presses down. I'm sure I accidentally deleted something or I need to change the hue values but not sure how...


int scn[];

void setup()
{
 size(600, 600);
 background(#ffffff);
 scn = new int[width*height];
 preserveScreen();
}

void draw()
{
 restoreScreen();
}

void mouseDragged() {
 alphaFrame(mouseX, mouseY);
}

void keyReleased() {
 fill(#ffffff);
 noStroke();
 ellipse(0, 0, width, height);
 preserveScreen();
}

void preserveScreen() {
 loadPixels();
 for (int i = 0; i < width*height; i++) {
   scn[i] = pixels[i];
 }
}

void restoreScreen() {
 for (int i = 0; i < width*height; i++) {
   pixels[i] = scn[i];
 }
 updatePixels();
}

void alphaFrame(float xin, float yin)
{
 int x = int(xin);
 int y = int(yin);
 int s = 200;
 s/=2;
 
 // the radius of the circle
 int radius = 50;
 for(int i=x-radius; i<x+radius; i++) {
   for(int j=y-radius; j<y+radius; j++) {
     // check if the pixel (i,j) is in the circle
     if (dist(i, j, x, y) < radius) {
       int rgb = scn[j*width + i];
       int r = (rgb >> 16) & 0xff;
       int g = (rgb >> 8) & 0xff;
       int b = rgb & 0xff;

       // first quadrant (12-3 oclock)
       if (x < i && j < y){
         if (r > 1) r--;
         if (g > 1) g--;

       // second quadrant (3-6 oclock)
       }
       else if(x < i && j > y){
         if (r < 255) r++;
         if (g < 255) g++;

       // third quadrant (6-9 oclock)
       }
       else if(x > i && j < y){
         if (g < 255) g--;

       // fourth quadrant (9-12 oclock)
       }
       else{
         if (g < 255) g++;
         
       scn[j*width + i] = 0xff000000 | (r << 16) | (g << 8) | (b);
       }
     }
   }
 }
}