离屏渲染

1、圆角使用UIImageView装载一个圆角图片来处理。

@implementation UIImage (RoundedCorner) 

- (UIImage *)imageWithRoundedCornersAndSize:(CGSize)sizeToFit andCornerRadius:(CGFloat)radius

{

　　 CGRect rect = (CGRect){0.f, 0.f, sizeToFit};

　　 UIGraphicsBeginImageContextWithOptions(sizeToFit, NO, UIScreen.mainScreen.scale); CGContextAddPath(UIGraphicsGetCurrentContext(), [UIBezierPath bezierPathWithRoundedRect:re ct cornerRadius:radius].CGPath); CGContextClip(UIGraphicsGetCurrentContext()); [self drawInRect:rect]; UIImage *output = UIGraphicsGetImageFromCurrentImageContext (); UIGraphicsEndImageContext();

    [self drawInRect:rect];

　　 UIImage *output = UIGraphicsGetImageFromCurrentImageContext();

　　　UIGraphicsEndImageContext();

　　　return output;

}@end

2、设置阴影

　　CALayer *shadowLayer = [CALayer layer];

　　shadowLayer = [UIColor blackColor].CGColor;

　　shadowLayer.shadowOpacity = 1.0;

　　shadowLayer.shadowRadius = 4.0;

　　shadowLayer.shadowOffset = CGSizeMake(4.0, 4.0); 

　以上可以使用shadowPath来解决，比如：

 shadowLayer.shadowPath = CGPathCreateWithRect(shadowLayer.bounds, NULL);

　　开发过程中最好不要让view透明。