OpenCV - Convert image to grayscale

1. /* load image */
2. IplImage *src = cvLoadImage( argv[1], CV_LOAD_IMAGE_COLOR );
3.  
4. /* get image properties */
5. width  = src->width;
6. height = src->height;
7.  
8. /* create new image for the grayscale version */
9. IplImage *dst = cvCreateImage( cvSize( width, height ), IPL_DEPTH_8U, 1 );
10.  
11. /* CV_RGB2GRAY: convert RGB image to grayscale */
12. cvCvtColor( src, dst, CV_RGB2GRAY );