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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) {
+ fprintf (stderr, "Out of memory.\n");
+ exit (1);
+ }
+ 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)
+{
+ int i;
+
+ 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];
+}