问题描述

iphone中的圆形相框效果

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();}