iphone中的圆形相框成效

原问题来自于CSDN问答频道，更多解决方案见：http://ask.csdn.net/questions/1908

想用下面的代码实现一个圆形相框：

CGContextRef context = CGBitmapContextCreate(NULL, self.bounds.size.width, self.bounds.size.height, 8, 4 * self.bounds.size.width, CGColorSpaceCreateDeviceRGB(), kCGImageAlphaPremultipliedFirst);CGContextAddArc(context, 1024/2, 768/2, size, 0, 6.3, 0);CGContextClosePath(context);CGContextClip(context);CGContextDrawImage(context, self.bounds, imageView.image.CGImage);CGImageRef imageMasked = CGBitmapContextCreateImage(context);CGContextRelease(context);UIImage *newImage = [UIImage imageWithCGImage:imageMasked];CGImageRelease(imageMasked);[imageView setImage:newImage];UIGraphicsEndImageContext();

在设置size--，圆形区域就会缩小，但是设置size++的时候，就没有反应。
不知道怎么呢？

解决方案：

你的代码修改成这样就可以了

- (IBAction)minus:(id)sender {    self.radius = @([self.radius floatValue]+10.0f);    [self redrawImage];}- (IBAction)plus:(id)sender {    self.radius = @([self.radius floatValue]-10.0f);    [self redrawImage];}-(void)redrawImage{    //set the original image first    [_imageView setImage:[UIImage imageNamed:@"your image goes here"]];    CGFloat size = [self.radius floatValue];    CGContextRef context = CGBitmapContextCreate(NULL, self.view.bounds.size.width, self.view.bounds.size.height, 8, 4 * self.view.bounds.size.width, CGColorSpaceCreateDeviceRGB(), kCGImageAlphaPremultipliedFirst);    CGContextAddArc(context, 320/2, 460/2, size, 0, 2*M_PI, 0);    CGContextClosePath(context);    CGContextClip(context);    CGContextDrawImage(context, self.view.bounds, _imageView.image.CGImage);    CGImageRef imageMasked = CGBitmapContextCreateImage(context);    CGContextRelease(context);    UIImage *newImage = [UIImage imageWithCGImage:imageMasked];    CGImageRelease(imageMasked);    [_imageView setImage:newImage];    UIGraphicsEndImageContext();}