调整图片方向

iOS-UIImage-FixOrientation

-(UIImage *)fixOrientation:(UIImage *)aImage
{
    if (aImage == nil)
    {
        return nil;
    }
    CGImageRef imgRef = aImage.CGImage;
    CGFloat width = CGImageGetWidth(imgRef);
    CGFloat height = CGImageGetHeight(imgRef);
    CGAffineTransform transform = CGAffineTransformIdentity;
    CGRect bounds = CGRectMake(0, 0, width, height);
    CGFloat scaleRatio = 1;
    CGFloat boundHeight;
    UIImageOrientation orient = aImage.imageOrientation;
    switch(orient) {
        case UIImageOrientationUp: //EXIF = 1
        {
            transform = CGAffineTransformIdentity;
            break;
        }
        case UIImageOrientationUpMirrored: //EXIF = 2
        {
            transform = CGAffineTransformMakeTranslation(width, 0.0);
            transform = CGAffineTransformScale(transform, -1.0, 1.0);
            break;
        }
        case UIImageOrientationDown: //EXIF = 3
        {
            transform = CGAffineTransformMakeTranslation(width, height);
            transform = CGAffineTransformRotate(transform, M_PI);
            break;
        }
        case UIImageOrientationDownMirrored: //EXIF = 4
        {
            transform = CGAffineTransformMakeTranslation(0.0, height);
            transform = CGAffineTransformScale(transform, 1.0, -1.0);
            break;
        }
        case UIImageOrientationLeftMirrored: //EXIF = 5
        {
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeTranslation(height, width);
            transform = CGAffineTransformScale(transform, -1.0, 1.0);
            transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
            break;
        }
        case UIImageOrientationLeft: //EXIF = 6
        {
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeTranslation(0.0, width);
            transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
            break;
        }
        case UIImageOrientationRightMirrored: //EXIF = 7
        {
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeScale(-1.0, 1.0);
            transform = CGAffineTransformRotate(transform, M_PI / 2.0);
            break;
        }
        case UIImageOrientationRight: //EXIF = 8
        {
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeTranslation(height, 0.0);
            transform = CGAffineTransformRotate(transform, M_PI / 2.0);
            break;
        }
        default:
        {
            [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"];
            break;
        }
    }
    UIGraphicsBeginImageContext(bounds.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft)
    {
        CGContextScaleCTM(context, -scaleRatio, scaleRatio);
        CGContextTranslateCTM(context, -height, 0);
    } else
    {
        CGContextScaleCTM(context, scaleRatio, -scaleRatio);
        CGContextTranslateCTM(context, 0, -height);
    }
    CGContextConcatCTM(context, transform);
    CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);
    UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return imageCopy;
}