-(void)drawRect:(CGRect)rect{CGContextRef ctx=UIGraphicsGetCurrentContext();CGContextBeginPath(ctx);CGContextAddRect(ctx, CGRectMake(100, 100, 100, 100));CGContextClip(ctx);//裁减，相对的CGContextClearRect是只留下矩形外面的
      CGContextBeginPath(ctx);CGContextAddRect(ctx, CGRectMake(0, 0, rect.size.width,   rect.size.height));[[UIColor brownColor]setFill];CGContextFillPath(ctx);
}

//绘制路径
CGMutablePathRef path=  CGPathCreateMutable();CGPathMoveToPoint(path, NULL, 20, 20);CFRelease(path);

//

CGContextAddPath(ctx, path1);

#pragma mark --截图
-(void)jitu{//切换到图片上下问
    UIGraphicsBeginImageContext(self.frame.size);//将view绘制到图形上下文中
    [self.layer renderInContext:UIGraphicsGetCurrentContext()];//将截屏保存到相册UIImage *newImage=UIGraphicsGetImageFromCurrentImageContext();UIImageWriteToSavedPhotosAlbum(newImage,self, @selector(image:didFinishSavingWithError:contextInfo:), nil);}- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo{if (error) {NSLog(@"保存失败，请检查是否拥有相关的权限");}else{NSLog(@"保存成功！");}}

//绘制图片  UIGraphicsBeginImageContextWithOptions( CGSizeMake(200, 200), NO, 0);//1.获取bitmap上下文CGContextRef ctx = UIGraphicsGetCurrentContext();//2.绘图(画一个圆)CGContextAddEllipseInRect(ctx, CGRectMake(0, 0, 100, 100));//3.渲染
             CGContextStrokePath(ctx);//4.获取生成的图片UIImage *image=UIGraphicsGetImageFromCurrentImageContext();//5.显示生成的图片到imageview
//             self.iv.image=image;//6.保存绘制好的图片到文件中//先将图片转换为二进制数据，然后再将图片写到文件中//    UIImageJPEGRepresentation(image, 1); //第二个参数为保存的图片的效果NSData *data=UIImagePNGRepresentation(image);[data writeToFile:@"/Users/liyang/Library/Developer/abc.png" atomically:YES];