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#include <stdlib.h>
#include "fast.h"
#define Compare(X, Y) ((X)>=(Y))
xy* nonmax_suppression(const xy* corners, const int* scores, int num_corners, int* ret_num_nonmax)
{
int num_nonmax=0;
int last_row;
int* row_start;
int i, j;
xy* ret_nonmax;
const int sz = (int)num_corners;
/*Point above points (roughly) to the pixel above the one of interest, if there
is a feature there.*/
int point_above = 0;
int point_below = 0;
if(num_corners < 1)
{
*ret_num_nonmax = 0;
return 0;
}
ret_nonmax = (xy*)malloc(num_corners * sizeof(xy));
/* Find where each row begins
(the corners are output in raster scan order). A beginning of -1 signifies
that there are no corners on that row. */
last_row = corners[num_corners-1].y;
row_start = (int*)malloc((last_row+1)*sizeof(int));
for(i=0; i < last_row+1; i++)
row_start[i] = -1;
{
int prev_row = -1;
for(i=0; i< num_corners; i++)
if(corners[i].y != prev_row)
{
row_start[corners[i].y] = i;
prev_row = corners[i].y;
}
}
for(i=0; i < sz; i++)
{
int score = scores[i];
xy pos = corners[i];
/*Check left */
if(i > 0)
if(corners[i-1].x == pos.x-1 && corners[i-1].y == pos.y && Compare(scores[i-1], score))
continue;
/*Check right*/
if(i < (sz - 1))
if(corners[i+1].x == pos.x+1 && corners[i+1].y == pos.y && Compare(scores[i+1], score))
continue;
/*Check above (if there is a valid row above)*/
if(pos.y != 0 && row_start[pos.y - 1] != -1)
{
/*Make sure that current point_above is one
row above.*/
if(corners[point_above].y < pos.y - 1)
point_above = row_start[pos.y-1];
/*Make point_above point to the first of the pixels above the current point,
if it exists.*/
for(; corners[point_above].y < pos.y && corners[point_above].x < pos.x - 1; point_above++)
{}
for(j=point_above; corners[j].y < pos.y && corners[j].x <= pos.x + 1; j++)
{
int x = corners[j].x;
if( (x == pos.x - 1 || x ==pos.x || x == pos.x+1) && Compare(scores[j], score))
goto cont;
}
}
/*Check below (if there is anything below)*/
if(pos.y != last_row && row_start[pos.y + 1] != -1 && point_below < sz) /*Nothing below*/
{
if(corners[point_below].y < pos.y + 1)
point_below = row_start[pos.y+1];
/* Make point below point to one of the pixels belowthe current point, if it
exists.*/
for(; point_below < sz && corners[point_below].y == pos.y+1 && corners[point_below].x < pos.x - 1; point_below++)
{}
for(j=point_below; j < sz && corners[j].y == pos.y+1 && corners[j].x <= pos.x + 1; j++)
{
int x = corners[j].x;
if( (x == pos.x - 1 || x ==pos.x || x == pos.x+1) && Compare(scores[j],score))
goto cont;
}
}
ret_nonmax[num_nonmax++] = corners[i];
cont:
;
}
free(row_start);
*ret_num_nonmax = num_nonmax;
return ret_nonmax;
}
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