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/** \file
* \brief Old resize/stretch functions
*
* See Copyright Notice in im_lib.h
* $Id: old_imresize.c,v 1.1 2008/10/17 06:10:16 scuri Exp $
*/
#include "old_im.h"
#include <stdlib.h>
#include <math.h>
#include <memory.h>
/*
BILINEAR INTERPOLATION:
x' = floor(x) f(x' , y') = fll
y' = floor(y) f(x' , y'+ 1) = flh
f(x'+ 1, y') = fhl
t = x - x' f(x'+ 1, y'+ 1) = fhh
u = y - y'
f(x,y) = (1-t) * (1-u) * f(x' , y'),
(1-t) * u * f(x' , y'+ 1),
t * (1-u) * f(x'+ 1, y'),
t * u * f(x'+ 1, y'+ 1)
f(x,y) = fll + (re-arranging)
t * (fhl - fll),
u * (flh - fll),
u * t * (fhh - flh - fhl + fll)
*/
void imResize(int src_width, int src_height, unsigned char *src_map, int dst_width, int dst_height, unsigned char *dst_map)
{
/* Do bilinear interpolation */
unsigned char *line_mapl, *line_maph;
double t, u, src_x, src_y, factor;
int fhh, fll, fhl, flh, xl, yl, xh, yh, x, y;
int *XL = (int*)malloc(dst_width * sizeof(int));
double *T = (double*)malloc(dst_width * sizeof(double));
factor = (double)(src_width-1) / (double)(dst_width-1);
for (x = 0; x < dst_width; x++)
{
src_x = x * factor;
xl = (int)floor(src_x);
T[x] = src_x - xl;
XL[x] = xl;
}
factor = (double)(src_height-1) / (double)(dst_height-1);
for (y = 0; y < dst_height; y++)
{
src_y = y * factor;
yl = (int)floor(src_y);
yh = (yl == src_height-1)? yl: yl + 1;
u = src_y - yl;
line_mapl = src_map + yl * src_width;
line_maph = src_map + yh * src_width;
for (x = 0; x < dst_width; x++)
{
xl = XL[x];
xh = (xl == src_width-1)? xl: xl + 1;
t = T[x];
fll = line_mapl[xl];
fhl = line_mapl[xh];
flh = line_maph[xl];
fhh = line_maph[xh];
*(dst_map++) = (unsigned char)(u * t * (fhh - flh - fhl + fll) + t * (fhl - fll) + u * (flh - fll) + fll);
}
}
free(XL);
free(T);
}
void imStretch(int src_width, int src_height, unsigned char *src_map, int dst_width, int dst_height, unsigned char *dst_map)
{
int x, y, offset;
double factor;
unsigned char *line_map;
int* XTab = (int*)malloc(dst_width*sizeof(int));
/* initialize convertion tables to speed up the stretch process */
factor = (double)(src_width-1) / (double)(dst_width-1);
for(x = 0; x < dst_width; x++)
XTab[x] = (int)(factor * x + 0.5);
factor = (double)(src_height-1) / (double)(dst_height-1);
line_map = src_map;
for (y = 0; y < dst_height; y++)
{
for (x = 0; x < dst_width; x++)
{
offset = XTab[x];
*(dst_map++) = line_map[offset];
}
offset = ((int)(factor * y + 0.5)) * src_width;
line_map = src_map + offset;
}
free(XTab);
}
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