ios - 使用UIIImagePicker的CGAffineTransform缩放UIImage并保存到Parse SDK

我使用以下代码缩放UIImagePickerController。

    CGAffineTransform translate = CGAffineTransformMakeTranslation(0.0, 71.0); //This slots the preview exactly in the middle of the screen by moving it down 71 points
    self.imagePicker.cameraViewTransform = translate;
    CGAffineTransform scale = CGAffineTransformScale(translate, 1.333333, 1.333333);
    self.imagePicker.cameraViewTransform = scale;

然后我拍张照片，并以UIImageView呈现

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

    [picker dismissViewControllerAnimated:NO completion:NULL];

    _imageTaken = nil;
    _imageTaken = [info objectForKey:UIImagePickerControllerEditedImage];
    if(_imageTaken==nil)
    {
        _imageTaken = [info objectForKey:UIImagePickerControllerOriginalImage];
    }
    if(_imageTaken==nil)
    {
        _imageTaken = [info objectForKey:UIImagePickerControllerCropRect];
    }

    [_imageTakenView setContentMode:UIViewContentModeScaleAspectFill];

    if (_selfie) {
        UIImage * flippedImage = [UIImage imageWithCGImage:_imageTaken.CGImage scale:_imageTaken.scale orientation:UIImageOrientationLeftMirrored];
        _imageTaken = flippedImage;
    }

    _imageTakenView.image = _imageTaken;
}

到目前为止一切都很好。然后，通过将图像转换为NSData将图像发送到数据库

    _imageData = [[NSData alloc] init];
    _imageData = UIImageJPEGRepresentation(_image, .1);

当我从服务器加载数据并将其以另一个相同大小的UIImageView呈现时，我确实设置了相同的宽高比:

    [_imageViewToShow setContentMode:UIViewContentModeScaleAspectFill];

但图像看起来失真(水平压缩)。关于为什么会这样的任何想法？

将UIImage转换为NSData并保存

_imageData = UIImageJPEGRepresentation(_image, .1);
PFFile *imageFile = [PFFile fileWithName:@"image.png" data:_imageData];
newMessage[@"image"] = imageFile;

问题:

当我重新下载数据时，UIImage看上去被压缩了。当我查看数据库中的图像时，看起来还不错。不知道为什么会这样...

图片之前和之后:

最佳答案

在上传之前尝试标准化图像的方向，即使元数据丢失，也可以使图像正常工作

这是执行此操作的类别:
UIImage+OrientationFix.h

@interface UIImage (OrientationFix)

- (UIImage*)imageByNormalizingOrientation;

@end

UIImage+OrientationFix.m

@implementation UIImage (OrientationFix)

- (UIImage*)imageByNormalizingOrientation {
    if (self.imageOrientation == UIImageOrientationUp)
        return self;

    CGSize size = self.size;
    UIGraphicsBeginImageContextWithOptions(size, NO, self.scale);
    [self drawInRect:(CGRect){{0, 0}, size}];
    UIImage* normalizedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return normalizedImage;
}

@end

您只需要致电:

_imageTaken = [flippedImage normalizedImage];