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POHow to do custom drawing in on a image in objective-c
 

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  1. POHow to do custom drawing in on a image in objective-c
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    <p>first of all i want to say that i'm newbie in objective-c.</p> <p>till know i have build an app that simply draws on one image (which is .png image that has 3 colors: red green blue). the applications draws lines in all over the image.</p> <p>what i want is to draw lines in only one color (ex: red), even if the touch (mouse) goes up the other colors. (... as I read on internet, it should be done using flood-fill algorithm)</p> <p>can you give me some ideas on how to to this.</p> <p>the code that i'm using now:</p> <pre><code>- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { mouseSwiped = YES; UITouch *touch = [touches anyObject]; currentPoint = [touch locationInView:self.view]; UIGraphicsBeginImageContext(CGSizeMake(320, 568)); [drawImage.image drawInRect:CGRectMake(0, 0, 320, 568)]; CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 5.0); CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0, 2, 0, 2); CGContextBeginPath(UIGraphicsGetCurrentContext()); CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y); CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y); CGContextStrokePath(UIGraphicsGetCurrentContext()); [drawImage setFrame:CGRectMake(0, 0, 320, 568)]; drawImage.image = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); lastPoint = currentPoint; [self.view addSubview:drawImage]; } </code></pre> <p>thnx in advance.</p>
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    1. CO[This post](http://stackoverflow.com/a/6064453/581994) gives some clues as to how to "open" an image and access the pixels.
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    2. CO`CGContextRef context = UIGraphicsGetCurrentContext();` would make that a lot more readable
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