Weird translation bug in this ...

gistfile1.txt

    // get source image
    NSData *imageData = _picture.imageData;
    CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)(imageData), NULL);
    CGImageRef sourceImage = CGImageSourceCreateImageAtIndex(source, 0, NULL);
    CFRelease(source);
    
    CGRect imageRect = CGRectZero;
    imageRect.size.width = CGImageGetWidth(sourceImage);
    imageRect.size.height = CGImageGetHeight(sourceImage);
    imageRect.origin.x = -imageRect.size.width/2.0;
    imageRect.origin.y = -imageRect.size.height/2.0;
    
    // move origin to image center
    CGContextTranslateCTM(context, outputSize.width/2.0, outputSize.height/2.0);
    
    // apply image rotation
    CGContextRotateCTM(context, -M_PI * _picture.editRotationDegrees/180.0);
    
    // apply offset
    CGContextTranslateCTM(context, _picture.editOffset.width, _picture.editOffset.height);

    // apply image scale
    CGContextScaleCTM(context, _picture.editScale, _picture.editScale);

    // draw image
    CGContextDrawImage(context, imageRect, sourceImage);