UIImage切圆角 - 优化

摘要: 好吧,这的却是老生常谈的问题,以前在网上找别人的方法切,但是自己用时候总是发现效果不很理想, 今天终于彻底解决了 ~

UIImage等比例缩放并切圆角

如题, 在网上找的代码也是可以用的, 但是问题是切成圆角时, 如果图片本身不是正方形就会导致图片变形,被压缩或者拉伸. 今上午阅读了那一段代码, 然后自己写出了任意长宽的图片, 都可以等比例缩放并切割成圆角图片, 默认切取图像正中央的位置.

[@interface](http://my.oschina.net/u/996807) UIImage (Extension)

///将UIImage图像切成圆形的图像, 指定宽度(边长)
- (UIImage *)circleImageWithWidth:(double)width;

///切成圆形的图片
- (UIImage *)cuttingCicleImageWithSize:(CGSize)size;

///缩放图片尺寸
- (UIImage *)zoomImageToSize:(CGSize)size;

///按照比例缩放图片, 原始图片为1, 参数(0~1)
- (UIImage *)zoomImageWithScale:(float)scale;

[@end](http://my.oschina.net/u/567204)

如下, 通过

- (UIImage *)circleImageWithWidth:(double)width

方法进行操作的,

第一步, 先将原始图片进行等比例缩放;

第二步, 截取等比缩放后正中央的正方形图片;

第三部, 将正方形图像切割成圆角图像.

@implementation UIImage (Extension)

///将UIImage图像切成圆形的图像, 指定宽度(边长)
- (UIImage *)circleImageWithWidth:(double)width {

// 计算一些变量, 供后面使用
float screenScale = [[UIScreen mainScreen] scale];
float scale = width / MIN(self.size.width, self.size.height);
CGSize originalScaleSize = CGSizeMake(self.size.width * scale, self.size.height * scale);
CGRect centerRange = CGRectOffset(CGRectMake(0, 0, width, width), (originalScaleSize.width-width)/2, (originalScaleSize.height-width)/2);

// 调用方法将图像缩放到指定的比例
UIImage *newImage = [self zoomImageWithScale:scale];

// 开始获取图片中间 正方形区域
CGImageRef imageRef = newImage.CGImage;
CGImageRef subImageRef = CGImageCreateWithImageInRect(imageRef, CGRectMake(centerRange.origin.x, centerRange.origin.y, centerRange.size.width * screenScale, centerRange.size.height * screenScale));
newImage = [UIImage imageWithCGImage:subImageRef];

//切成圆角并返回图像
return [newImage cuttingCicleImageWithSize:CGSizeMake(width, width)];
}

///切成圆形的图片
- (UIImage *)cuttingCicleImageWithSize:(CGSize)size {

double screenScale = [[UIScreen mainScreen] scale];
CGRect rect = CGRectMake(0, 0, size.width, size.height);

UIGraphicsBeginImageContextWithOptions(size, NO, screenScale);
CGContextRef ctx = UIGraphicsGetCurrentContext();

CGContextAddEllipseInRect(ctx, rect);
CGContextClip(ctx);
[self drawInRect:rect];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

return newImage;
}

///缩放图片尺寸
- (UIImage *)zoomImageToSize:(CGSize)size {

UIGraphicsBeginImageContextWithOptions(size, NO, [[UIScreen mainScreen] scale]);
[self drawInRect:CGRectMake(0, 0, size.width, size.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

return newImage;
}

///按照比例缩放图片, 原始图片为1, 参数(0~1)
- (UIImage *)zoomImageWithScale:(float)scale {

CGSize targetSize = CGSizeMake(self.size.width * scale, self.size.height * scale);
return [self zoomImageToSize:targetSize];
}

[@end](http://my.oschina.net/u/567204)