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/*
Laplacian Pyramid
Copyright (C) 2006 Yangli Hector Yee
This program is free software; you can redistribute it and/or modify it under the terms of the
GNU General Public License as published by the Free Software Foundation; either version 2 of the License,
or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program;
if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
*/
#include "lpyramid.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct _lpyramid {
/* Successively blurred versions of the original image */
float *levels[MAX_PYR_LEVELS];
int width;
int height;
};
static void
convolve (lpyramid_t *pyramid, float *a, const float *b)
/* convolves image b with the filter kernel and stores it in a */
{
int y,x,i,j;
const float Kernel[] = {0.05f, 0.25f, 0.4f, 0.25f, 0.05f};
int width = pyramid->width;
int height = pyramid->height;
for (y=0; y<height; y++) {
for (x=0; x<width; x++) {
float sum = 0.f;
for (j=-2; j<=2; j++) {
float sum_i = 0.f;
int ny=y+j;
if (ny<0) ny=-ny;
if (ny>=height) ny=2*height - ny - 1;
ny *= width;
for (i=-2; i<=2; i++) {
int nx=x+i;
if (nx<0) nx=-nx;
if (nx>=width) nx=2*width - nx - 1;
sum_i += Kernel[i+2] * b[ny + nx];
}
sum += sum_i * Kernel[j+2];
*a++ = sum;
* Construction/Destruction
lpyramid_t *
lpyramid_create (float *image, int width, int height)
lpyramid_t *pyramid;
int i;
pyramid = malloc (sizeof (lpyramid_t));
if (pyramid == NULL) {
fprintf (stderr, "Out of memory.\n");
exit (1);
pyramid->width = width;
pyramid->height = height;
/* Make the Laplacian pyramid by successively
* copying the earlier levels and blurring them */
for (i=0; i<MAX_PYR_LEVELS; i++) {
pyramid->levels[i] = malloc (width * height * sizeof (float));
if (pyramid->levels[i] == NULL) {
if (i == 0) {
memcpy (pyramid->levels[i], image, width * height * sizeof (float));
} else {
convolve(pyramid, pyramid->levels[i], pyramid->levels[i - 1]);
return pyramid;
void
lpyramid_destroy (lpyramid_t *pyramid)
for (i=0; i<MAX_PYR_LEVELS; i++)
free (pyramid->levels[i]);
free (pyramid);
float
lpyramid_get_value (lpyramid_t *pyramid, int x, int y, int level)
int index = x + y * pyramid->width;
int l = level;
if (l > MAX_PYR_LEVELS)
l = MAX_PYR_LEVELS;
return pyramid->levels[l][index];