/**      *  剪切图片为正方形      *      *  @param image   原始图片比如size大小为(400x200)pixels      *  @param newSize 正方形的size比如400pixels      *      *  @return 返回正方形图片(400x400)pixels      */      - (UIImage *)squareImageFromImage:(UIImage *)image scaledToSize:(CGFloat)newSize {          CGAffineTransform scaleTransform;          CGPoint origin;                    if (image.size.width > image.size.height) {              //image原始高度为200，缩放image的高度为400pixels，所以缩放比率为2              CGFloat scaleRatio = newSize / image.size.height;              scaleTransform = CGAffineTransformMakeScale(scaleRatio, scaleRatio);              //设置绘制原始图片的画笔坐标为CGPoint(-100, 0)pixels              origin = CGPointMake(-(image.size.width - image.size.height) / 2.0f, 0);          } else {              CGFloat scaleRatio = newSize / image.size.width;              scaleTransform = CGAffineTransformMakeScale(scaleRatio, scaleRatio);                            origin = CGPointMake(0, -(image.size.height - image.size.width) / 2.0f);          }                    CGSize size = CGSizeMake(newSize, newSize);          //创建画板为(400x400)pixels          if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)]) {              UIGraphicsBeginImageContextWithOptions(size, YES, 0);          } else {              UIGraphicsBeginImageContext(size);          }                    CGContextRef context = UIGraphicsGetCurrentContext();          //将image原始图片(400x200)pixels缩放为(800x400)pixels          CGContextConcatCTM(context, scaleTransform);          //origin也会从原始(-100, 0)缩放到(-200, 0)          [image drawAtPoint:origin];                    //获取缩放后剪切的image图片          image = UIGraphicsGetImageFromCurrentImageContext();                    UIGraphicsEndImageContext();                    return image;      }