UIImagePickerController显示正确的图像，直到我保存图像

Question

我正在使用UIImagePickerController获取UIImage。获得图像后，我将其设置为UITableView的背景。这张图片看起来和我拍的一模一样。但如果我把图片保存到服务器上，然后再加载回来。无论我使用UIImagePNGRepresentation还是UIImageJPEGRepresentation保存，图像都会在保存时旋转（旋转发生在服务器调用之前）。我在这里读到png会旋转，但jpeg不会。但对我来说，两者都旋转90度。有什么想法吗，为什么jpeg在我的情况下不好？

更多

我从图像选择器中获取原始图像作为UIImage。然后我保留一个指向UIImage的指针。一段时间后，我想保存UIImage。所以通常我做UIImagePNGRepresentation(myUIImage)。我正在使用AFNetworking作为

if ([self.imageDictionaries count]>0)
  for (NSDictionary *imgDic in self.imageDictionaries) {
    [formData appendPartWithFileData:UIImagePNGRepresentation([imgDic objectForKey:@"image"])
    name:[imgDic objectForKey:@"name"]//@"image"
    fileName:[imgDic objectForKey:@"fileName"]//@"image.png"
    mimeType:[imgDic objectForKey:@"mimeType"]//@"image/png"
    ];
  }
}
//[imgDic objectForKey:@"name"] is just a UIImage

imageDictionaries的其中一个项目看起来像这个

NSDictionary *background =@{
                                @"image":self.backgroundImage,
                                @"name":@"bkgimg",
                                @"fileName":@"bkgimg.png",
                                @"mimeType":@"image/png"
                                };

还要注意，我的代码运行良好。唯一的问题是图像正在旋转。self.backgroundImage是指向我作为从UIImagePickerController获得的UIImage的指针

UIImage *background = info[UIImagePickerControllerOriginalImage];

如果使用UIImagePickerControllerEditedImage，则图像不会旋转。但这是另一个时代的另一个故事。

Answer 1

不要用UIImagePNGRrepresentation或UIImageJPEGRepresentation保存它。使用ImageIO框架。这样可以使用正确的旋转信息进行保存。

或者，根据你正在做的事情（你没有确切解释你是如何获得这些图像的），通过CGImage可能就足够了。您可以将旋转信息附加到它上，同时将其包装为UIImage。

Answer 2

图像正在旋转，因为您将图像保存为JPEG，如果您将图像存储为PNG，则方向不会更改。这是修复定向问题的代码。

- (UIImage *)fixrotation:(UIImage *)image{

if (image.imageOrientation == UIImageOrientationUp) return image;
CGAffineTransform transform = CGAffineTransformIdentity;
switch (image.imageOrientation) {
    case UIImageOrientationDown:
    case UIImageOrientationDownMirrored:
        transform = CGAffineTransformTranslate(transform, image.size.width, image.size.height);
        transform = CGAffineTransformRotate(transform, M_PI);
        break;
    case UIImageOrientationLeft:
    case UIImageOrientationLeftMirrored:
        transform = CGAffineTransformTranslate(transform, image.size.width, 0);
        transform = CGAffineTransformRotate(transform, M_PI_2);
        break;
    case UIImageOrientationRight:
    case UIImageOrientationRightMirrored:
        transform = CGAffineTransformTranslate(transform, 0, image.size.height);
        transform = CGAffineTransformRotate(transform, -M_PI_2);
        break;
    case UIImageOrientationUp:
    case UIImageOrientationUpMirrored:
        break;
}
switch (image.imageOrientation) {
    case UIImageOrientationUpMirrored:
    case UIImageOrientationDownMirrored:
        transform = CGAffineTransformTranslate(transform, image.size.width, 0);
        transform = CGAffineTransformScale(transform, -1, 1);
        break;
    case UIImageOrientationLeftMirrored:
    case UIImageOrientationRightMirrored:
        transform = CGAffineTransformTranslate(transform, image.size.height, 0);
        transform = CGAffineTransformScale(transform, -1, 1);
        break;
    case UIImageOrientationUp:
    case UIImageOrientationDown:
    case UIImageOrientationLeft:
    case UIImageOrientationRight:
        break;
}
// Now we draw the underlying CGImage into a new context, applying the transform
// calculated above.
CGContextRef ctx = CGBitmapContextCreate(NULL, image.size.width, image.size.height,
                                         CGImageGetBitsPerComponent(image.CGImage), 0,
                                         CGImageGetColorSpace(image.CGImage),
                                         CGImageGetBitmapInfo(image.CGImage));
CGContextConcatCTM(ctx, transform);
switch (image.imageOrientation) {
    case UIImageOrientationLeft:
    case UIImageOrientationLeftMirrored:
    case UIImageOrientationRight:
    case UIImageOrientationRightMirrored:
        // Grr...
        CGContextDrawImage(ctx, CGRectMake(0,0,image.size.height,image.size.width), image.CGImage);
        break;
    default:
        CGContextDrawImage(ctx, CGRectMake(0,0,image.size.width,image.size.height), image.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; 
}