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/*
* $Id: resample.c,v 1.11 2010/02/05 23:50:22 simakov Exp $
*
* EPSILON - wavelet image compression library.
* Copyright (C) 2006,2007,2010 Alexander Simakov, <xander@entropyware.info>
*
* This file is part of EPSILON
*
* EPSILON is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* EPSILON 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with EPSILON. If not, see <http://www.gnu.org/licenses/>.
*
* http://epsilon-project.sourceforge.net
*/
#include <common.h>
#include <resample.h>
void bilinear_resample_channel(coeff_t **input_channel, coeff_t **output_channel,
int input_width, int input_height,
int output_width, int output_height)
{
coeff_t t, u;
coeff_t tmp;
int i, j;
int l, c;
/* Sanity checks */
assert((input_width > 1) && (input_height > 1));
assert((output_width > 1) && (output_height > 1));
for (i = 0; i < output_height; i++) {
for (j = 0; j < output_width; j++) {
tmp = (double) (input_height - 1) *
((double) i / (double) (output_height - 1));
l = (int) tmp;
if (l < 0) {
l = 0;
} else if (l >= input_height - 1) {
l = input_height - 2;
}
u = tmp - (double) l;
tmp = (double) (input_width - 1) *
((double) j / (double) (output_width - 1));
c = (int) tmp;
if (c < 0) {
c = 0;
} else if (c >= input_width - 1) {
c = input_width - 2;
}
t = tmp - (double) c;
output_channel[i][j] =
input_channel[l][c] * (1 - t) * (1 - u) +
input_channel[l + 1][c] * (1 - t) * u +
input_channel[l][c + 1] * t * (1 - u) +
input_channel[l + 1][c + 1] * t * u;
}
}
}
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