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绘制具有圆角的图片(可以配置圆角半径、边框、填充色)，用途：具有圆角效果的场景，节省性能，告别离屏渲染，用法：简单，比如只需要把生成的图片放到视图底部即可
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| /** | |
| 绘制具有圆角的图片(可以配置圆角半径、边框、填充色)， | |
| 用途：具有圆角效果的场景，节省性能，告别离屏渲染， | |
| 用法：简单，比如只需要把生成的图片放到视图底部即可 | |
| @param radius 圆角大小 | |
| @param borderWidth 边框宽度 | |
| @param borderColor 边框颜色 | |
| @param fillColor 填充色(如果不需要，可以传入[UIColor clearColor]) | |
| @param size 图形上下文大小(绘制区域大小) | |
| @return 生成的具有圆角的图片 | |
| */ | |
| + (UIImage *)drawRectWithRoundedCornerWithRadius:(CGFloat)radius borderWidth:(CGFloat)borderWidth borderColor:(UIColor *)borderColor fillColor:(UIColor *)fillColor forContextSize:(CGSize)size | |
| { | |
| CGFloat halfOfBorderWidth = borderWidth / 2.0; | |
| /*根据指定选项(Options)创建基于位图的上下文 */ | |
| UIGraphicsBeginImageContextWithOptions(size, false, [UIScreen mainScreen].scale); | |
| CGContextRef ctx = UIGraphicsGetCurrentContext(); | |
| /*设置边框和填充色*/ | |
| CGContextSetLineWidth(ctx, borderWidth); | |
| CGContextSetStrokeColorWithColor(ctx, borderColor.CGColor); | |
| CGContextSetFillColorWithColor(ctx, fillColor.CGColor); | |
| CGFloat width = size.width; | |
| CGFloat height = size.height; | |
| CGFloat realRadius = radius - halfOfBorderWidth; | |
| /*绘制边框和圆角*/ | |
| CGContextMoveToPoint(ctx, width - halfOfBorderWidth, radius - halfOfBorderWidth); // 开始坐标右边开始 | |
| CGContextAddArcToPoint(ctx, width - halfOfBorderWidth , height - halfOfBorderWidth, width - radius - halfOfBorderWidth, height - halfOfBorderWidth, realRadius); // 右下角 | |
| CGContextAddArcToPoint(ctx, halfOfBorderWidth, height - halfOfBorderWidth, halfOfBorderWidth, height - radius - halfOfBorderWidth, realRadius); // 左下角 | |
| CGContextAddArcToPoint(ctx, halfOfBorderWidth, halfOfBorderWidth, width - halfOfBorderWidth - radius, halfOfBorderWidth, realRadius); // 左上角 | |
| CGContextAddArcToPoint(ctx, width - halfOfBorderWidth, halfOfBorderWidth, width - halfOfBorderWidth, radius + halfOfBorderWidth, realRadius); // 右上角 | |
| CGContextDrawPath(ctx, kCGPathFillStroke); | |
| UIImage *out = UIGraphicsGetImageFromCurrentImageContext(); | |
| /*和UIGraphicsBeginImageContextWithOptions成对出现，从栈中移除基于位图的上下文*/ | |
| UIGraphicsEndImageContext(); | |
| return out; | |
| } |
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