iOS屏幕截图功能

iOS7.0之前的系统，可以通过以下代码实现截屏功能。

- (UIImage *)captureImageFromView:(UIView *)view{ 
    CGRect screenRect = view.bounds;
    UIGraphicsBeginImageContext(screenRect.size);
    CGContextRef contextRef = UIGraphicsGetCurrentContext();
    [view.layer renderInContext:contextRef];
    UIImage *returnImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return returnImage;
 // UIImage.size == view.bounds.size
}

iOS7.0之后，系统中封装了截屏的方法
- (UIView *)snapshotViewAfterScreenUpdates:(BOOL)afterUpdates
方法调用示例

UIView *redView = [[UIView alloc]initWithFrame:CGRectMake(100, 300, 200, 200)]; redView.backgroundColor = [UIColor redColor];
[self.view addSubview:redView]; 
UIView *captureView = [redView snapshotViewAfterScreenUpdates:YES];
[self.view addSubview:captureView]; 
// captureView.frame == (0,0,200,200)

截屏效果图