source: proiecte/pmake3d/make3d_original/Make3dSingleImageStanford_version0.1/third_party/torr/torr_max3x3.c @ 37

/*
max3.c     implements ...

  goes through and tests to see if the pixel is a maximum in its 3x3 neighbourhood

  2001 written by Phil Torr
  Microsoft Research Cambridge
*/

#include <math.h>
#include <stdio.h>
#include "mex.h"

void mexFunction (
                                  int           nlhs,              /* number of expected outputs */
                                  mxArray       **plhs,            /* matrix pointer array returning outputs */
                                  int           nrhs,              /* number of inputs */
                                  const mxArray **prhs     /* matrix pointer array for inputs */
                                  ) {
        int       width, height, i, j, l, k, border =1;
        double    *out, *in, max;
        bool is_max;
        
        /* parameter checks */
        if ((nrhs != 1) || (nlhs != 1)) {
                mexErrMsgTxt ("Usage: Y = max3 (im1)\n\n");
                return;
        }
        
        /* reading the parameters */
        height = mxGetM (prhs [0]);
        width = mxGetN (prhs [0]);
        in = (double *) mxGetPr (prhs [0]);
        
        /* require memory for return */
        plhs [0] = mxCreateDoubleMatrix (height, width, mxREAL);
        out = (double *) mxGetPr (plhs [0]);
        

        //fill in border pixels with a negative...
        for (i = 0; i < height; i++)
        {
                j = 0; 
                out [j * height + i] = -10001.0;
                j = width-1; 
                out [j * height + i] = -10001.0;
        }

        
        //fill in border pixels with a negative...
        for (j = border; j < width-border; j++)
        {
                i = 0;
                out [j * height + i] = -10001.0;
                i = height-1; 
                out [j * height + i] = -10001.0;
        }

        
        /* check for maximum */
        for (i = border; i < height-border; i++)
                for (j = border; j < width-border; j++) {
                        max = in [j * height + i]; 
                        is_max = true;
                        if (max >0.0)
                        {
                                /* finding the maximum in the neighbourhood */
                                for (l = -border; l < border+1; l++)
                                        for (k = -border; k < border+1; k++) 
                                                if (in [(j + l) * height + (i + k)] >= max) {
                                                        if ((l!=0) || (k!=0))
                                                                //max = in [(j + l) * height + (i + k)];
                                                                is_max = false;
                                                }
                        }
                        else
                                is_max = false; //if not over threshold, here zero
                        if (is_max)
                                out [j * height + i] = max;
                        else
                                out [j * height + i] = -10001.0;
                }
                
                return;
}