在UIImageView IOS中绘制形状

Question

我试图在UIImageView中使用特定图像绘制一些圆圈.这就是我想要做的事情:

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];

圆圈绘制得很好,但我希望PhotoView充当它的遮罩.因此,例如,如果我使用动画将UIImageView移出UIView,我希望圆圈随之移动.重要的是坐标相对于整个屏幕.

Answer 1

请改用Core Animation的形状图层.

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];

现在,如果您为包含此图层的UIImageView设置动画,该图层将随之移动,因为它是子图层.现在没有必要覆盖drawRect:.