need some math help (uv wrap/statue related)

Hello,

so I'm absolutely not the best in math but I know it should be possible.

I'm trying to uv wrap image data to a statue by using the cropped images to make a basic cuboid model first, but now I wonder how would I calculate it so that it gets the correct pixel from the full image rather than the cropped ones?

from what ive seen for example with schematics it had a special way of calculating the data such like int data = width * length - height, forgive me for the bad math

I'm pretty sure the same principe of doing that works on images to, but I'm clueless what I need todo there.

my code what ive already(yes I know it only does it for one leg rather than 2, need to understand first how wrapping works)

Code:

public class LegsComponent {
    private final BufferedImage image;
    private final Location loc;
    public LegsComponent(BufferedImage image, Location loc) {
        this.image = image;
        this.loc = loc;
    }
    public BufferedImage getCroppedRightLeg() {
        return crop(0, 20, 4, 32);
    }
    public BufferedImage getCroppedFrontLeg() {
        return crop(4, 20, 8, 32);
    }
    public BufferedImage getCroppedLeftLeg() {
        return crop(8, 20, 12, 32);
    }
    public BufferedImage getCroppedBackLeg() {
        return crop(12, 20, 16, 32);
    }
    public LinkedHashMap<Location, String> getLegs() {
        LinkedHashMap<Location, String> hash = new LinkedHashMap<Location, String>();
        int height = getCroppedFrontLeg().getHeight();
        int width = getCroppedFrontLeg().getWidth();
        int length = getCroppedLeftLeg().getWidth();
        Location loc1 = loc.clone();
        loc1.setX(loc1.getX()-(width/2));
        loc1.setZ(loc1.getZ()-(length/2));
        for(int y = 0; y < height; y++) {
            for(int x = 0; x < width; x++) {
                for(int z = 0; z < length; z++) {
                    //here I need to get the pixel from the full 'image' field.
                }
            }
        }
        
        return hash;
    }
    private BufferedImage crop(int minX, int minY, int maxX, int maxY) {
        BufferedImage img = image.getSubimage(minX, minY, maxX, maxY);
        BufferedImage copy = new BufferedImage(img.getWidth(), img.getHeight(), BufferedImage.TYPE_INT_RGB);
        Graphics g = copy.createGraphics();
        g.drawImage(img,0,0,null);
        return img;
    }
}

the field above the constructor called image is the full image and is linked from http://minecraft.net/skin/Xeph0re.png

any help is apreciated, or better workarounds are welcome

thanks.