private static PImage img;
private static short  y;

void setup () {
    size(800, 600);
    background(0);
    imageMode(CORNER);
    frameRate(100);

    img = loadImage("Turner.jpg");  //  load background image
    image(img, 0, 0);  //  stamp image to screen as background
}

void draw () {

    // picks another random color for line:
    stroke( (color) random(0x1000000) | 0xff000000 );

    // draws a full line, dot by dot:
    for ( short x=0; x<width; point(x++, y) );

    if (++y == height) {  // goes to next line
        y = 0;            // if last line drawn, restarts from the beginning
        image(img, 0, 0); // and re-stamps image over screen, erasing all
    }
}

1. int[] arrayred = new int[607500];
2. int[] arraygreen = new int[607500];
3. int[] arrayblue = new int[607500];
4. PImage img;
5. int x = 0;
6. int y = 0;
7. 
   
8. void setup () {
9.   size(900, 675);
10.   img = loadImage("Turner.jpg");
11.   // image(img, 0, 0);
12.   //background(255);
13. }
14. 
    
15. void draw () {
16.   img.loadPixels();
17.   for (int i = 0; i < img.pixels.length; i++) {
18.     color pix = img.pixels[i];
19.     int r = (pix >> 16) & 0xFF;
20.     int g = (pix >> 8) & 0xFF;
21.     int b = (pix >> 0) & 0xFF;
22.     arrayred[i] = r;
23.     arraygreen[i] = g;
24.     arrayblue [i] = b;
25.     fill(r, g, b); 
26.     rect(width/2, height/2, 50, 50);
27.     println(r + " " + g + " " + b);
28.   }
29.   point(x, y);
30.   x = x + 1;
31.   if ( x == 900) {
32.     x = 0;
33.     y = y + 1;
34.   }
35. }

private static PImage img;
private static short  y;
private static final byte fps = 100;

void setup () {
    size(1200, 800);
    imageMode(CORNER);
    frameRate(fps);

    img = loadImage("Turner.jpg");  // load background image
}

void draw () {

    background(0);
    image(img, 0, y); // stamp image to screen as background

    //if (++y == height)  y = 0;   // scroll down
    if (--y == -img.height) y = 0; // scroll up
}

This works well, however it still does not draw a Rect or a point when the code is ran.

Thank you, but this isn't what I'm looking for.

1. int[] arrayred, arraygreen, arrayblue;
2. PImage img;
3. int imgWidth;
4. int nbrPixels;
5. int currPixelNo;
6. void setup () {
7.   size(900, 675);
8.   img = loadImage("Turner.jpg");
9.   nbrPixels = img.width * img.height;
10.   arrayred = new int[nbrPixels];
11.   arraygreen = new int[nbrPixels];
12.   arrayblue = new int[nbrPixels];
13.   currPixelNo = 0;
14.   imgWidth = img.width;
15.   background(255);
16.   image(img, 0, 0);
17.   img.loadPixels();
18. }
19. void draw () {
20.   if (currPixelNo < nbrPixels) {
21.     color pix = img.pixels[currPixelNo];
22.     int r = (pix >> 16) & 0xFF;
23.     int g = (pix >> 8) & 0xFF;
24.     int b = (pix >> 0) & 0xFF;
25.     arrayred[currPixelNo] = r;
26.     arraygreen[currPixelNo] = g;
27.     arrayblue [currPixelNo] = b;
28.     fill(r, g, b); 
29.     set(imgWidth + currPixelNo % imgWidth, currPixelNo / imgWidth, pix);
30.     currPixelNo++;
31.     println(currPixelNo + "        " + imgWidth);
32.   }
33. }