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Draw a grid of images using Core Graphics in drawRect:

My problem is this: I have a simple block image from which I want to make a grid. I created an array of CGPoints in my UIView. Then i used

blackImage = [UIImage imageNamed:@"black.png"];

and then

- (void)drawRect:(CGRect)rect {
    for (int j = 0 ; j <= 11; j++)
    {
        for (int i = 0 ; i <= 7; i++) 
        {
            [blackImage drawAtPoint: (CGPointFromString([[self.points objectAtIndex:j] objectAtIndex:i]))];
        }
    }
    [whiteImage drawAtPoint:(CGPointMake((CGFloat)(floor((touchX+0.001)/40)*40), (CGFloat)(floor((touchY+0.001)/40))*40))];

    //  [whiteImage drawAtPoint:(CGPointMake(240.0, 320.0))];   
}

Where TouchX and TouchY are CGPoints where the user touched the screen. Therefore, I basically show another image at the grid point where the user touched.

First of all, the problem is that the whole screen is redrawn every time I call DrawRect. I want to save state (by changing the BOOL array?) And ask the user to drag and drop multiple images onto the screen. However, I cannot use the drawAtPoint method in UImage when I am outside of DrawRect. (gives an error message).

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