拍照获得的照片，在ImageView中显示时方向有问题的解决方法

创建一个UIImage的类扩展：UIImage+Extension，在.m文件中写如下方法：

- ( 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;

}

调用方式：UIImage * fixedImage = oldImage.fixOrientation;