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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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
#include "LPyramid.h"
// Construction/Destruction
LPyramid::LPyramid(const float *image, int width, int height) :
// Make the Laplacian pyramid by successively
// copying the earlier levels and blurring them
for (int i=0; i<MAX_PYR_LEVELS; i++) {
if (i == 0) {
Levels[i] = Copy(image);
} else {
Levels[i] = new float[Width * Height];
Convolve(Levels[i], Levels[i - 1]);
for (int i=0; i<MAX_PYR_LEVELS; i++) {
delete [] Levels[i];
float *LPyramid::Copy(const float *img) const
int max = Width * Height;
float *out = new float[max];
for (int i = 0; i < max; i++) out[i] = img[i];
return out;
void LPyramid::Convolve(float *a, const float *b) const
// convolves image b with the filter kernel and stores it in a
const float Kernel[] = {0.05f, 0.25f, 0.4f, 0.25f, 0.05f};
#pragma omp parallel for
for (int y=0; y<Height; y++) {
for (int x=0; x<Width; x++) {
int index = y * Width + x;
a[index] = 0.0f;
for (int i=-2; i<=2; i++) {
for (int j=-2; j<=2; j++) {
int nx=x+i;
int ny=y+j;
if (nx<0) nx=-nx;
if (ny<0) ny=-ny;
if (nx>=Width) nx=2*Width-nx-1;
if (ny>=Height) ny=2*Height-ny-1;
a[index] += Kernel[i+2] * Kernel[j+2] * b[ny * Width + nx];
float LPyramid::Get_Value(int x, int y, int level) const
int index = x + y * Width;
int l = level;
if (l >= MAX_PYR_LEVELS) l = MAX_PYR_LEVELS - 1;
return Levels[l][index];
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