iOS - UIImageView - how to handle UIImage image orientation

本文转载至 http://stackoverflow.com/questions/8915630/ios-uiimageview-how-to-handle-uiimage-image-orientation

Is it possible to setup UIImageView to handle image orientation? When I set the UIImageView to image with orientation RIGHT (it is photo from camera roll), the image is rotated to right, but I want to show it in proper orientation, as it was taken.

I know I can rotate image data but it is possible to do it more elegant?

Thank you

ios uiimageview uiimage orientation

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asked Jan 18 '12 at 18:49

Martin Pilch
1,14021441

4 Answers

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up vote54down voteaccepted

If I understand, what you want to do is disregard the orientation of the UIImage? If so then you could do this:

UIImage *originalImage = [... whatever ...];

UIImage *imageToDisplay =

     [UIImage imageWithCGImage:[originalImage CGImage]

              scale:1.0

              orientation: UIImageOrientationUp];

So you're creating a new UIImage with the same pixel data as the original (referenced via its CGImage property) but you're specifying an orientation that doesn't rotate the data.

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answered Jan 18 '12 at 19:05

Tommy
69.7k9107125

By the way, how can I actually rotate the image data? – Eno Mar 8 '12 at 7:19

I guess you'd create a suitably sized CGContext with CGBitmapContextCreate (or with theUIGraphicsBeginImageContext shorthand), use CGContextRotateCTM to set a rotation, use eitherdrawInRect: on the UIImage or CGContextDrawImage with the image's CGImage property, then convert the context to an image either with UIGraphicsGetImageFromCurrentImageContext (and, then,UIGraphicsEndImageContext) if you used UIKit to create the context, orCGBitmapContextCreateImage if you were sticking with the Core Graphics. UIKit isn't very thread safe, but the code would be neater. – Tommy Mar 8 '12 at 20:31

Thanks, I've got it over! – Eno Mar 10 '12 at 8:10

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up vote20down vote

As Anomie suggests in their answer here, this code will help to fix orientation:

- (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;

}

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edited Sep 3 '13 at 2:00

Brad Larson♦
136k31307465

answered Feb 23 '13 at 10:44

suvish valsan
556621

and seems to have been copied from stackoverflow.com/questions/5427656/… – Geoff Hackworth May 27 '13 at 8:34

It's kinda sad how he got 11 up votes for plagiarism. – Rambatino Nov 17 '14 at 19:56

Also note that CGContextDrawImage takes about 40MB for a 5MB image... – Yerk Mar 9 at 19:12

@Yerk do you know what I can do instead, to stop this huge file increase? – TimWhiting Apr 1 at 10:56

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up vote9down vote

You can completely avoid manually doing the transforms and scaling yourself, as suggested by an0 in this answer here:

- (UIImage *)normalizedImage {

    if (self.imageOrientation == UIImageOrientationUp) return self; 

    UIGraphicsBeginImageContextWithOptions(self.size, NO, self.scale);

    [self drawInRect:(CGRect){0, 0, self.size}];

    UIImage *normalizedImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return normalizedImage;

}

The documentation for the UIImage methods size and drawInRect explicitly states that they take into account orientation.

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answered Jul 15 '14 at 23:57

user2067021
1,028916

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up vote4down vote

here is a workable sample cod, considering the image orientation:

#define rad(angle) ((angle) / 180.0 * M_PI)

- (CGAffineTransform)orientationTransformedRectOfImage:(UIImage *)img

{

    CGAffineTransform rectTransform;

    switch (img.imageOrientation)

    {

        case UIImageOrientationLeft:

            rectTransform = CGAffineTransformTranslate(CGAffineTransformMakeRotation(rad(90)), 0, -img.size.height);

            break;

        case UIImageOrientationRight:

            rectTransform = CGAffineTransformTranslate(CGAffineTransformMakeRotation(rad(-90)), -img.size.width, 0);

            break;

        case UIImageOrientationDown:

            rectTransform = CGAffineTransformTranslate(CGAffineTransformMakeRotation(rad(-180)), -img.size.width, -img.size.height);

            break;

        default:

            rectTransform = CGAffineTransformIdentity;

    };

    return CGAffineTransformScale(rectTransform, img.scale, img.scale);

}

- (UIImage *)croppedImage:(UIImage*)orignialImage InRect:(CGRect)visibleRect{

    //transform visible rect to image orientation

    CGAffineTransform rectTransform = [self orientationTransformedRectOfImage:orignialImage];

    visibleRect = CGRectApplyAffineTransform(visibleRect, rectTransform);

    //crop image

    CGImageRef imageRef = CGImageCreateWithImageInRect([orignialImage CGImage], visibleRect);

    UIImage *result = [UIImage imageWithCGImage:imageRef scale:orignialImage.scale orientation:orignialImage.imageOrientation];

    CGImageRelease(imageRef);

    return result;

}

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巴特西

iOS - UIImageView - how to handle UIImage image orientation

4 Answers

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