I've tried a combination of other posts, the Learning section, and the book Processing, by Reas and Fry. Try as I might, I just can't figure out how to do this. I need Processing to load a black and white image, and store the coordinates of all black pixels in 2 arrays: 1 for their x-axis, and the other for their y-axis. How can I do this?

Here's what I have so far:

1. PImage img;
   int[] xArray;
   int[] yArray;
   
   void setup() {
     size(100,100);
     img = loadImage("image.jpg");
   }
   
   void draw() {
     background(0);
     image(img,0,0);
    
     //Load the pixels
     loadPixels();
     //Loop through each pixel
     for (int ix = 0; ix < pixels.length; ix++) {
       for (int iy = 0; iy < pixels.length; iy++) {
         //Set col to the color at that pixel
         int col = color(get(ix,iy));
         //If the color is less than 20 on an RGB scale (to include dark gray)
         if (col < 20) {
           //Add the X and Y coordinates to their respective array
           append(xArray,ix);
           append(yArray,iy);
       }
       }
     }
   }