ios 防止相册取图片旋转

+(UIImage *)fixOrientation:(UIImage *)aImage {

    

    // No-op if the orientation is already correct

    if (aImage.imageOrientation ==UIImageOrientationUp)

        return aImage;

    

    // 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 (aImage.imageOrientation) {

        caseUIImageOrientationDown:

        caseUIImageOrientationDownMirrored:

            transform = CGAffineTransformTranslate(transform, aImage.size.width, aImage.size.height);

            transform = CGAffineTransformRotate(transform, M_PI);

            break;

            

        caseUIImageOrientationLeft:

        caseUIImageOrientationLeftMirrored:

            transform = CGAffineTransformTranslate(transform, aImage.size.width,0);

            transform = CGAffineTransformRotate(transform, M_PI_2);

            break;

            

        caseUIImageOrientationRight:

        caseUIImageOrientationRightMirrored:

            transform = CGAffineTransformTranslate(transform,0, aImage.size.height);

            transform = CGAffineTransformRotate(transform, -M_PI_2);

            break;

        default:

            break;

    }

    

    switch (aImage.imageOrientation) {

        caseUIImageOrientationUpMirrored:

        caseUIImageOrientationDownMirrored:

            transform = CGAffineTransformTranslate(transform, aImage.size.width,0);

            transform = CGAffineTransformScale(transform, -1,1);

            break;

            

        caseUIImageOrientationLeftMirrored:

        caseUIImageOrientationRightMirrored:

            transform = CGAffineTransformTranslate(transform, aImage.size.height,0);

            transform = CGAffineTransformScale(transform, -1,1);

            break;

        default:

            break;

    }

    

    // Now we draw the underlying CGImage into a new context, applying the transform

    // calculated above.

    CGContextRef ctx =CGBitmapContextCreate(NULL, aImage.size.width, aImage.size.height,

                                             CGImageGetBitsPerComponent(aImage.CGImage),0,

                                             CGImageGetColorSpace(aImage.CGImage),

                                             CGImageGetBitmapInfo(aImage.CGImage));

    CGContextConcatCTM(ctx, transform);

    switch (aImage.imageOrientation) {

        caseUIImageOrientationLeft:

        caseUIImageOrientationLeftMirrored:

        caseUIImageOrientationRight:

        caseUIImageOrientationRightMirrored:

            // Grr...

            CGContextDrawImage(ctx,CGRectMake(0,0,aImage.size.height,aImage.size.width), aImage.CGImage);

            break;

            

        default:

            CGContextDrawImage(ctx,CGRectMake(0,0,aImage.size.width,aImage.size.height), aImage.CGImage);

            break;  

    }  

    

    // And now we just create a new UIImage from the drawing context  

    CGImageRef cgimg =CGBitmapContextCreateImage(ctx);  

    UIImage *img = [UIImageimageWithCGImage:cgimg];  

    CGContextRelease(ctx);  

    CGImageRelease(cgimg);  

    return img;  

}