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POHow to make a subview tint a portion of the screen on the iPhone?
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  1. POHow to make a subview tint a portion of the screen on the iPhone?
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    copied!<p>I would like to write a UIView subclass that, among other things, colors whatever's underneath it a certain color. This is what I've come up with, but it unfortunately doesn't seem to work correctly:</p> <pre><code>#import &lt;UIKit/UIKit.h&gt; @class MyOtherView; @interface MyView : UIView { MyOtherView *subview; } @end @implementation MyView - (id)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { frame.origin.x += 100.0; frame.origin.y += 100.0; frame.size.width = frame.size.height = 200.0; subview = [[MyOtherView alloc] initWithFrame:frame]; [self addSubview:subview]; [subview release]; } return self; } - (void)drawRect:(CGRect)rect { // Draw a background to test out on UIImage *image = [UIImage imageNamed:@"somepic.png"]; [image drawAtPoint:rect.origin]; const CGContextRef ctx = UIGraphicsGetCurrentContext(); [[UIColor blueColor] setFill]; rect.size.width = rect.size.height = 200.0; CGContextFillRect(ctx, rect); } @end @interface MyOtherView : UIView @end @implementation MyOtherView - (void)drawRect:(CGRect)rect { // This should tint "MyView" but it doesn't. const CGContextRef ctx = UIGraphicsGetCurrentContext(); CGContextSaveGState(ctx); CGContextSetBlendMode(ctx, kCGBlendModeScreen); [[UIColor redColor] setFill]; CGContextFillRect(ctx, rect); CGContextRestoreGState(ctx); } @end </code></pre> <p>I want "MyOtherView" to color "MyView" red where it overlaps, but instead it just draws an opaque red block onto it. However, this seems work fine if I copy the -drawRect: function from "MyOtherView" and append it to the one in "MyView" (this took me quite a headache to finally realize). Anyone know what I'm doing wrong? Is it even possible to do this, or should I be approaching it differently?</p>
 

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