Scaling UIImage with a UIIImagePicker's CGAffineTransform and Saving to Parse SDK

问题

I use the following code to scale my 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;

Then I take the picture and present it in a UIImageView

- (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;
}

Everything is good so far. Then I send the image up to my database by converting it to NSData

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

When I load the data back from the server and present it in another UIImageView of the same size I do set the same aspect ratio:

    [_imageViewToShow setContentMode:UIViewContentModeScaleAspectFill];

but the image looks distored (squished horizontally). Any ideas as to why this might be?

Convert UIImage to NSData & Save

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

Problem:

When I redownload the data, the UIImage appears squished. When I look at the image on my database, it seems fine. Not sure why this is happening...

Before and After Images:

回答1:

Try normalizing the image's orientation before uploading.This will allow the image to work properly even if the metadata is lost

Here is a category to do that:

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

You will just have to call:

_imageTaken = [flippedImage normalizedImage];

来源：https://stackoverflow.com/questions/23769310/scaling-uiimage-with-a-uiiimagepickers-cgaffinetransform-and-saving-to-parse-sd

标签

ios

objective-c

uiimageview

uiimage