解决UIImage图片上传旋转

iOS程序中使用系统相机拍照和从相册选取图片，直接上传后在非mac系统下看到的图片会发生旋转的现象，那是因为我们没有通过图片的旋转属性修改图片倒置的。下面的方法可以很简单的解决旋转问题：

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@interface UIImage (fixOrientation)     - (UIImage *)fixOrientation;     @end             @implementation UIImage (fixOrientation)     - (UIImage *)fixOrientation {         // No-op if the orientation is already correct     if (self.imageOrientation == UIImageOrientationUp) return self;         // We need to calculate the proper transformation to make the image upright.     // We do it in 2 steps: Rotate if Left/Right/Down, and then flip if Mirrored.     CGAffineTransform transform = CGAffineTransformIdentity;         switch (self.imageOrientation) {         case UIImageOrientationDown:         case UIImageOrientationDownMirrored:             transform = CGAffineTransformTranslate(transform, self.size.width, self.size.height);             transform = CGAffineTransformRotate(transform, M_PI);             break;             case UIImageOrientationLeft:         case UIImageOrientationLeftMirrored:             transform = CGAffineTransformTranslate(transform, self.size.width, 0);             transform = CGAffineTransformRotate(transform, M_PI_2);             break;             case UIImageOrientationRight:         case UIImageOrientationRightMirrored:             transform = CGAffineTransformTranslate(transform, 0, self.size.height);             transform = CGAffineTransformRotate(transform, -M_PI_2);             break;     }         switch (self.imageOrientation) {         case UIImageOrientationUpMirrored:         case UIImageOrientationDownMirrored:             transform = CGAffineTransformTranslate(transform, self.size.width, 0);             transform = CGAffineTransformScale(transform, -1, 1);             break;             case UIImageOrientationLeftMirrored:         case UIImageOrientationRightMirrored:             transform = CGAffineTransformTranslate(transform, self.size.height, 0);             transform = CGAffineTransformScale(transform, -1, 1);             break;     }         // Now we draw the underlying CGImage into a new context, applying the transform     // calculated above.     CGContextRef ctx = CGBitmapContextCreate(NULL, self.size.width, self.size.height,                                              CGImageGetBitsPerComponent(self.CGImage), 0,                                              CGImageGetColorSpace(self.CGImage),                                              CGImageGetBitmapInfo(self.CGImage));     CGContextConcatCTM(ctx, transform);     switch (self.imageOrientation) {         case UIImageOrientationLeft:         case UIImageOrientationLeftMirrored:         case UIImageOrientationRight:         case UIImageOrientationRightMirrored:             // Grr...             CGContextDrawImage(ctx, CGRectMake(0,0,self.size.height,self.size.width), self.CGImage);             break;             default:             CGContextDrawImage(ctx, CGRectMake(0,0,self.size.width,self.size.height), self.CGImage);             break;     }         // And now we just create a new UIImage from the drawing context     CGImageRef cgimg = CGBitmapContextCreateImage(ctx);     UIImage *img = [UIImage imageWithCGImage:cgimg];     CGContextRelease(ctx);     CGImageRelease(cgimg);     return img; }     @end