Can anyone tell me how to use the UIImagePickerController (camera and album) delegates determine the image's orientation, rotate accordingly, and assign it to a UIImageView?
Iphone – UIImagePickerController Image Orientation
cocoa-touchexifiphoneorientationuiimagepickercontroller
Related Solutions
I just started working on this issue in my own app.
I used the UIImage category that Trevor Harmon crafted for resizing an image and fixing its orientation, UIImage+Resize.
Then you can do something like this in -imagePickerController:didFinishPickingMediaWithInfo:
UIImage *pickedImage = [info objectForKey:UIImagePickerControllerEditedImage]; UIImage *resized = [pickedImage resizedImageWithContentMode:UIViewContentModeScaleAspectFit bounds:pickedImage.size interpolationQuality:kCGInterpolationHigh];
This fixed the problem for me. The resized image is oriented correctly visually and the imageOrientation property reports UIImageOrientationUp.
There are several versions of this scale/resize/crop code out there; I used Trevor's because it seems pretty clean and includes some other UIImage manipulators that I want to use later.
A UIImage
has a property imageOrientation
, which instructs the UIImageView
and other UIImage
consumers to rotate the raw image data. There's a good chance that this flag is being saved to the exif data in the uploaded jpeg image, but the program you use to view it is not honoring that flag.
To rotate the UIImage
to display properly when uploaded, you can use a category like this:
UIImage+fixOrientation.h
@interface UIImage (fixOrientation)
- (UIImage *)fixOrientation;
@end
UIImage+fixOrientation.m
@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;
case UIImageOrientationUp:
case UIImageOrientationUpMirrored:
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;
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, 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
Best Answer
Vodkhang's answer is partially incorrect - modern cameras put an explicit orientation into the image when they take the photo. This has been common for about 5+ years now.
I've previously used the code in this answer to do the rotation by reading the "orientation" info direct from the picture:
UIImagePickerController camera preview is portrait in landscape app