gistfile1.m

static inline double radians (double degrees) {return degrees * M_PI/180;}

CGImageRef CreateRotatedImage(CGImageRef imageRef, UIImageOrientation orientation)
{
    CGRect             bnds = CGRectZero;
    CGImageRef         copy = nil;
    CGContextRef       ctxt = nil;
    CGRect             rect = CGRectZero;
    CGAffineTransform  tran = CGAffineTransformIdentity;

    bnds.size = CGSizeMake(CGImageGetWidth(imageRef), CGImageGetHeight(imageRef)); //self.size;
    rect.size = CGSizeMake(CGImageGetWidth(imageRef), CGImageGetHeight(imageRef)); //self.size;

    switch (orientation)
    {
        case UIImageOrientationUp:
            return imageRef;

        case UIImageOrientationUpMirrored:
            tran = CGAffineTransformMakeTranslation(rect.size.width, 0.0);
            tran = CGAffineTransformScale(tran, -1.0, 1.0);
            break;

        case UIImageOrientationDown:
            tran = CGAffineTransformMakeTranslation(rect.size.width, rect.size.height);
            tran = CGAffineTransformRotate(tran, radians(180.0));
            break;

        case UIImageOrientationDownMirrored:
            tran = CGAffineTransformMakeTranslation(0.0, rect.size.height);
            tran = CGAffineTransformScale(tran, 1.0, -1.0);
            break;
        default:
            // orientation value supplied is invalid
            assert(false);
            return nil;
    }

    UIGraphicsBeginImageContext(bnds.size);
    ctxt = UIGraphicsGetCurrentContext();

    switch (orientation)
    {
        case UIImageOrientationLeft:
        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
            CGContextScaleCTM(ctxt, -1.0, 1.0);
            CGContextTranslateCTM(ctxt, -rect.size.height, 0.0);
            break;

        default:
            CGContextScaleCTM(ctxt, 1.0, -1.0);
            CGContextTranslateCTM(ctxt, 0.0, -rect.size.height);
            break;
    }

    CGContextConcatCTM(ctxt, tran);
    CGContextDrawImage(ctxt, rect, imageRef);

    copy = CGBitmapContextCreateImage(ctxt);
    UIGraphicsEndImageContext();

    return copy;
}