I'm working on a sketch (targeted for fullscreen in Present mode) that draws a grid of random colored squares to the screen at a given scale. This happens every frame, and I'm using a PGraphics as an offscreen buffer.

The following code does exactly what I need and runs fine on my computer, but it eats up about 20% of my CPU. Since it's such a simple operation, I suspect there's probably a better way to do it I don't know about.

1. PGraphics canvas;
2. final int scale = 5; // side length of squares
3. final int xCenter = displayWidth / 2;
4. final int yCenter = displayHeight / 2;
5. 
   
6. void setup() {
7.   size(displayWidth, displayHeight, P2D);
   
8.   canvas = createGraphics(displayWidth, displayHeight, P2D);
9.   canvas.imageMode(CENTER);
10. }
        
    
11. void draw() {
12.   canvas.beginDraw();
13.   canvas.noStroke();
14.   for(int i = 0; i < displayWidth; i+=scale) {
15.     for(int j = 0; j < displayHeight; j+=scale) {
16.       canvas.fill(random(255), random(255), random(255));
17.       canvas.rect(i, j, scale, scale);
18.     }
19.   }
20.   canvas.endDraw();
21.   image(canvas, xCenter, yCenter);
22. }
    

Any insight on how I might be able to achieve the same effect in a more efficient way?