waveproc.c

来自「wavlet compression on c++ only cods」· C语言 代码 · 共 82 行

// Copyright (c) 1999 Stephen T. Welstead. All rights reserved.
// waveproc.c  Procedures for wavelet processing

#include <malloc.h>
#include <math.h>
#include "waveproc.h"

int decimate_array (float **array,int rows,int cols,
	  unsigned long n) {
     /* Set all but the largest amplitude n array elements equal to 0 */
     /* Array indexes start at 1.  */
     tindex *indexes;
     int i,j;
     unsigned long k,count = 0;
     int min_index,start_row,start_col;
     float min;
     if (n == 0) {
	for (i=1;i<=rows;i++)
	    for (j=1;j<=cols;j++)
		array[i][j] = 0.0;
        return 1;
	}
     if (!(indexes = malloc ((size_t)(n+1)*sizeof(tindex)))) return 0;
     /* Initialize index list and minimum: */
     min = fabs(array[1][1]);
     min_index = 1;
     for (i=1;i<=rows;i++) {
	 for (j=1;j<=cols;j++) {
	     count++;
	     indexes[count].row = i;
	     indexes[count].col = j;
	     if (fabs(array[i][j]) < min) {
		min = fabs(array[i][j]);
		min_index = count;
		}
	     start_row = i;
	     start_col = j;
	     if (count == n) break;
	     }  /* end j */
	 if (count == n) break;
	 }  /* end i */
     /* Finish this row  */
     for (j=start_col+1;j<=cols;j++)
	 if (fabs(array[start_row][j]) > min) {
	    /* Set array min list element equal to 0 */
	    array[indexes[min_index].row][indexes[min_index].col] = 0.0;
	    /* Replace min element in list with this new element */
	    indexes[min_index].row = start_row;
	    indexes[min_index].col = j;
	    /* search for new min in index list: */
	    min = fabs(array[start_row][j]);
	    for (k=1;k<=n;k++)
		if (fabs(array[indexes[k].row][indexes[k].col]) < min) {
		   min = fabs(array[indexes[k].row][indexes[k].col]);
		   min_index = k;
		   }
	    } /*  end if, j  */
     else array[start_row][j] = 0.0;  /* not a candidate for list */
     for (i=start_row+1;i<=rows;i++)
     for (j=1;j<=cols;j++)
	 if (fabs(array[i][j]) > min) {
	    /* Set array min list element equal to 0 */
	    array[indexes[min_index].row][indexes[min_index].col] = 0.0;
	    /* Replace min element in list with this new element */
	    indexes[min_index].row = i;
	    indexes[min_index].col = j;
	    /* search for new min in index list: */
	    min = fabs(array[i][j]);
	    for (k=1;k<=n;k++)
		if (fabs(array[indexes[k].row][indexes[k].col]) < min) {
		   min = fabs(array[indexes[k].row][indexes[k].col]);
		   min_index = k;
		   }
	    } /*  end if, i,j  */
     else array[i][j] = 0.0;  /* not a candidate for list */
     free (indexes);
     return 1;
     }