在UIImageView中繪製形狀IOS

Question

我想用一個特定的圖像在UIImageView中繪製一些圓圈。這就是我要怎樣做：

UIGraphicsBeginImageContext(self.view.bounds.size); 
CGContextRef contextRef = UIGraphicsGetCurrentContext(); 
CGContextSetLineWidth(contextRef, 2.0); 
CGContextSetStrokeColorWithColor(contextRef, [color CGColor]); 
CGRect circlePoint = (CGRectMake(coordsFinal.x, coordsFinal.y, 50.0, 50.0)); 

CGContextStrokeEllipseInRect(contextRef, circlePoint); 

UIImage *image = UIGraphicsGetImageFromCurrentImageContext(); 
UIGraphicsEndImageContext(); 

[photoView addSubview:image]; 

圓圈繪製精細，但我想在PhotoView中充當面膜吧。所以，如果例如我使用動畫將UIImageView移出UIView，我希望圓圈隨之移動。重要的是座標是相對於整個屏幕的事實。

Answer 1

改爲使用Core Animation的形狀圖層。現在

CAShapeLayer *circleLayer = [CAShapeLayer layer]; 
// Give the layer the same bounds as your image view 
[circleLayer setBounds:CGRectMake(0.0f, 0.0f, [photoView bounds].size.width, 
               [photoView bounds].size.height)]; 
// Position the circle anywhere you like, but this will center it 
// In the parent layer, which will be your image view's root layer 
[circleLayer setPosition:CGPointMake([photoView bounds].size.width/2.0f, 
            [photoView bounds].size.height/2.0f)]; 
// Create a circle path. 
UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect: 
            CGRectMake(0.0f, 0.0f, 50.0f, 50.0f)]; 
// Set the path on the layer 
[circleLayer setPath:[path CGPath]]; 
// Set the stroke color 
[circleLayer setStrokeColor:[[UIColor redColor] CGColor]]; 
// Set the stroke line width 
[circleLayer setLineWidth:2.0f]; 

// Add the sublayer to the image view's layer tree 
[[photoView layer] addSublayer:circleLayer]; 

，如果動畫包含這層的UIImageView，該層將它，因爲它是一個子層移動。現在不需要重寫drawRect:。