UITableView性能－圆角图片

圆角图片因为GPU渲染会影响性能

参考：http://www.cocoachina.com/ios/20150803/12873.html

http://blog.sina.com.cn/s/blog_671d2e4f0101cxpl.html

http://www.cnblogs.com/thefeelingofsimple/archive/2013/02/20/2918547.html 

instruments用的不多，我直接循环了几个圆角，3种方法试了下

 image.layer.cornerRadius = 8;
 image.layer.masksToBounds = YES;

上面效率是最低的，

另外的重写draw方法，和mask图与原图覆盖生成新图，效率感觉差不多，等后面熟悉了instruments在测试下，

重写drawRect,(-_-,要弄个新的属性才会走这里，本菜鸟还不懂啊，先弄了个UIImageView用它自己的image走都不走这里。。。图形这方面设计太少了)

//注意背景色要和cell的背景色设置一致哦，不然－0-
- (void)drawRect:(CGRect)rect {
    CGRect bounds = self.bounds;
    [[UIColor whiteColor]set];
    UIRectFill(bounds);
    [[UIBezierPath bezierPathWithRoundedRect:rect cornerRadius:8.0] addClip];
    [self.image drawInRect:bounds];
}

- (void)setImage:(UIImage *)image {
    _image = image;
    //需要这一步，需要刷新，不然显示会出问题
    [self setNeedsDisplay];
}

- (void)dealloc {
    self.image = nil;
}

mask图与原图覆盖生成新图

- (UIImage *)imageByComposingImage:(UIImage *)image withMaskImage:(UIImage *)maskImage {
    CGImageRef maskImageRef = maskImage.CGImage;
    CGImageRef maskRef = CGImageMaskCreate(CGImageGetWidth(maskImageRef),
                                           CGImageGetHeight(maskImageRef),
                                           CGImageGetBitsPerComponent(maskImageRef),
                                           CGImageGetBitsPerPixel(maskImageRef),
                                           CGImageGetBytesPerRow(maskImageRef),
                                           CGImageGetDataProvider(maskImageRef), NULL, false);
    
    CGImageRef newImageRef = CGImageCreateWithMask(image.CGImage, maskRef);
    CGImageRelease(maskRef);
    UIImage *newImage = [UIImage imageWithCGImage:newImageRef];
    CGImageRelease(newImageRef);
    
    return newImage;
}

补充：mask图与原图覆盖生成新图可以自定义任意形状的图哦

测试demo链接：http://pan.baidu.com/s/1qWCDprY