// In an outer scope, you might have...

IplImage*  draw_image    = cvCreateImage(cvSize (640,480), IPL_DEPTH_8U, 3);
IplImage*  warp_image    = cvCreateImage(cvSize (640,480), IPL_DEPTH_8U, 3);
IplImage*  gs_image      = cvCreateImage(cvSize (640,480), IPL_DEPTH_8U, 1);
IplImage*  corner_image  = cvCreateImage(cvSize (640,480), IPL_DEPTH_32F, 1);

float thresh = 1.5;
int block_size = 7;
int aperture_size = 3;
double k = 0.04;


// I used key presses to change the parameters above to reasonable values...


// within a processing loop, then, you could use...

                // get draw_image from a camera or a file...

                // convert to grayscale
		cvCvtColor( draw_image, gs_image, CV_RGB2GRAY );

                // get Harris corners!
		cvCornerHarris( gs_image, corner_image, block_size, aperture_size, k );

                // find min and max for scaling...
		double min_val = 1.0e9;
		double max_val = -1.0;
		CvPoint min_loc;
		CvPoint max_loc;
		cvMinMaxLoc( corner_image, &min_val, &max_val, &min_loc, &max_loc, NULL ); // NULL mask

		// scale the corner_image to [0,1]
		double scale_factor = 1.0/(max_val - min_val);
		double shift_amt = fabs( scale_factor * min_val );
		cvConvertScale( corner_image, corner_image, scale_factor, shift_amt ); // now from 0 to 1
                // make sure this works...
		//cvMinMaxLoc( corner_image, &min_val, &max_val, &min_loc, &max_loc, NULL ); // it checks out...

                // let's see it...
		cvShowImage(WINDOW_NAME, corner_image);

                // then we can threshold...
		int H = corner_image->height;
		int W = corner_image->width;
		IplImage* img = corner_image;
		for (int row=1 ; row<H-1 ; ++row ) {
			for (int col=1 ; col<W-1 ; ++col) {
				// pixel access described at http://opencv.willowgarage.com/wiki/faq#Howtoaccessimagepixels
				float* px = ((float*)(img->imageData + img->widthStep*row));
				float px_val = px[col];
				// check for local max in a 3x3 square...

                                // we'll leave this to you...

                                // here, we'll just check the threshold
                                if (px_val > thresh)
                                {
					px[col] = 1.0;
				} else {
					px[col] = 0.0;
				}
			}
		}

		// we could show this instead...
		//cvShowImage(WINDOW_NAME, corner_image);