對UIImage做左右顛倒的轉換

#import <QuartzCore/QuartzCore.h>

+ (UIImage*)transformImageSymmetrically:(UIImage*)originalImage
{
    UIImage *transformedImage = originalImage;
    if (!isUsingBackCamera) {
 

        //建立一個暫存用的UIImageView
        UIImageView *tempImageView = [[UIImageView alloc] initWithImage:originalImage];
 

        
        UIGraphicsBeginImageContext(tempImageView.frame.size);

        
        //這三行跟下面mark起來的七行，效果是一樣的，可以互相取代

        CGContextRef context = UIGraphicsGetCurrentContext();
        CGAffineTransform flipHorizontal = CGAffineTransformMake(                                                               -1.0, 0.0, 0.0, 1.0, tempImageView.frame.size.width, 0.0 );
        CGContextConcatCTM(context, flipHorizontal);
//        CGImageRef imgRef = originalImage.CGImage;
//        CGFloat width = CGImageGetWidth(imgRef);
//        CGFloat height = CGImageGetHeight(imgRef);
//        CGAffineTransform transform = CGAffineTransformIdentity;  
//        transform = CGAffineTransformMakeTranslation(width,0.0);
//        transform = CGAffineTransformScale(transform, -1.0, 1.0);
//        CGContextConcatCTM(context, transform);
        [tempImageView.layer renderInContext:context];
        
        transformedImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        [tempImageView release];
        
    }
    return transformedImage;
}