一般情況下我們給UIKit控件添加圓角都是改變clipsToBounds和layer.cornerRadius,這樣雖然看似簡(jiǎn)單虱而，兩行代碼就可以搞定霞势。但是，這樣使用會(huì)強(qiáng)制Core Animation提前渲染屏幕的離屏繪制患整，而離屏繪制就會(huì)為性能帶來(lái)負(fù)面影響眯停。
下面為大家提供一種比較復(fù)雜的方式來(lái)為控件添加圓角：

#import <UIKit/UIKit.h>

@interface UIView (RoundedCorner)

// 設(shè)置頂部圓角
- (void)setRoundedCornerOnTop;

// 設(shè)置底部圓角
- (void)setRoundedCornerOnBottom;

// 設(shè)置圓角
- (void)setRoundedCorner;

// 取消圓角
- (void)removeRoundedCorner;

// 自定義圓角大小 scale范圍：0 ~ 0.5
- (void)setRoundedCornerWithScale:(CGFloat)scale;

// 自定義頂部圓角大小 scale范圍：0 ~ 0.5
- (void)setRoundedCornerOnTopWithScale:(CGFloat)scale;

// 自定義底部圓角大小 scale范圍：0 ~ 0.5
- (void)setRoundedCornerOnBottomWithScale:(CGFloat)scale;

@end

#import "UIView+RoundedCorner.h"

@implementation UIView (RoundedCorner)

- (void)setRoundedCornerOnTop {
    [self setRoundedCornerOnTopWithScale:0.5];
}

- (void)setRoundedCornerOnBottom {
    [self setRoundedCornerOnBottomWithScale:0.5];
}

- (void)setRoundedCorner {
    [self setRoundedCornerWithScale:0.5];
}

- (void)removeRoundedCorner {
    self.layer.mask = nil;
}

- (void)setRoundedCornerWithScale:(CGFloat)scale {
    if (scale > 0.5) {
        scale = 0.5;
    }
    UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:self.bounds cornerRadius:self.frame.size.height * scale];
    [self setShapeLayer:maskPath];
}

- (void)setRoundedCornerOnTopWithScale:(CGFloat)scale {
    if (scale > 0.5) {
        scale = 0.5;
    }
    UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:self.bounds byRoundingCorners:UIRectCornerTopLeft | UIRectCornerTopRight cornerRadii:CGSizeMake(self.frame.size.height * scale, self.frame.size.height * scale)];
    [self setShapeLayer:maskPath];
}

- (void)setRoundedCornerOnBottomWithScale:(CGFloat)scale {
    if (scale > 0.5) {
        scale = 0.5;
    }
    UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:self.bounds byRoundingCorners:UIRectCornerBottomLeft | UIRectCornerBottomRight cornerRadii:CGSizeMake(self.frame.size.height * scale, self.frame.size.height * scale)];
    [self setShapeLayer:maskPath];
}

// 創(chuàng)建CAShapeLayer并設(shè)置
- (void)setShapeLayer:(UIBezierPath *)maskPath {
    CAShapeLayer *maskLayer = [CAShapeLayer layer];
    maskLayer.frame = self.bounds;
    maskLayer.path = maskPath.CGPath;
    self.layer.mask = maskLayer;
}

@end

當(dāng)然還有給UIImageView添加圓角的方法济舆。（注意：如果加載的是網(wǎng)絡(luò)圖片，必須要等網(wǎng)絡(luò)圖片加載完成再調(diào)用）

#import <UIKit/UIKit.h>

@interface UIImageView (RoundedCorner)

- (UIImageView *)imageViewWithRoundedCornerSize:(CGFloat)cornerRadius;

@end

#import "UIImageView+RoundedCorner.h"

@implementation UIImageView (RoundedCorner)

- (UIImageView *)imageViewWithRoundedCornerSize:(CGFloat)cornerRadius {
    UIImageView *imageView = self;
    UIImage *original = self.image;
    
    UIGraphicsBeginImageContextWithOptions(imageView.bounds.size, NO, 1.0);
    [[UIBezierPath bezierPathWithRoundedRect:imageView.bounds cornerRadius:cornerRadius] addClip];
    [original drawInRect:imageView.bounds];
    imageView.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return imageView;
}

@end

代碼Demo點(diǎn)這里：http://git.oschina.net/chocklee/RoundedCorner