Using jimp to get hex values of pixels of an image and then find a square within it in NOde.JS

Question

I have an image, then the goal is to detect large rectangles of the same color within an image.

So if an image is uploaded with a square picture of a duck on the left, and a square picture of another duck on top, the largest rectangle can be found toward the bottom right side.

Here is what I know so far:

Jimp.read("imagepath", function (err, image) {
    image.getPixelColor(x, y); 
});

What I think I should do somehow to accomplish this, is:

Jimp.read("imagepath", function (err, image) { 
    for(var x = 0; x < Jimp.Pixel.Length?; x++) {
       for(var y...) {


           image.getPixelColor(x, y); 
     }
});

So somehow converting the image into an array of pixels that is like a 2d array. Then going through the array and using code to find patterns that match a rectangle.