libtthimage/Lib/halfsize.c

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2022-06-27 00:48:18 +02:00
/*
halfsize.c
------------------
see also: scale.c doublesz.c
*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "../tthimage.h"
/*::------------------------------------------------------------------::*/
/*
* Fabrication d'une image moiti<EFBFBD> de l'image source.
*
* cette fonction alloue une _nouvelle_ image
* ==========
* m<EFBFBD>thodes:
* 0: primitive.
* 1: semblant d'interpolation.
*
*/
Image_Desc *
Image_MakeHalfSize(Image_Desc *image, int methode)
{
int largeur, hauteur, x, y, xx, yy;
Image_Desc *demi;
largeur = image->width / 2; hauteur = image->height / 2;
if (image->type != IMAGE_RGB)
{
fprintf(stderr, "Image HalfSize: bad image type %d\n", image->type);
return NULL;
}
#if DEBUG_LEVEL
fprintf(stderr, "MakeHalfSize: from %dx%d, method %d -> %d x %d\n",
image->width, image->height, methode, largeur, hauteur);
#endif
demi = Image_alloc(largeur, hauteur, image->type);
if ( demi == NULL )
{
fprintf(stderr, "Image make half size: no memory\n");
exit(5);
}
/*
* ne faudrait-il pas transmettre certains des attributs de
* l'image originale <EFBFBD> la nouvelle image ?
*/
demi->modified = 0;
demi->errmsg = image->errmsg;
for (y=0; y<hauteur; y++)
{
yy = y * 2;
for (x=0; x<largeur; x++)
{
xx = x * 2;
switch(methode)
{
case 0:
(demi->Rpix[y])[x] = (image->Rpix[yy])[xx];
(demi->Gpix[y])[x] = (image->Gpix[yy])[xx];
(demi->Bpix[y])[x] = (image->Bpix[yy])[xx];
break;
case 1:
(demi->Rpix[y])[x] = ( (image->Rpix[yy])[xx] +
(image->Rpix[yy+1])[xx] +
(image->Rpix[yy])[xx+1] +
(image->Rpix[yy+1])[xx+1] ) / 4;
(demi->Gpix[y])[x] = ( (image->Gpix[yy])[xx] +
(image->Gpix[yy+1])[xx] +
(image->Gpix[yy])[xx+1] +
(image->Gpix[yy+1])[xx+1] ) / 4;
(demi->Bpix[y])[x] = ( (image->Bpix[yy])[xx] +
(image->Bpix[yy+1])[xx] +
(image->Bpix[yy])[xx+1] +
(image->Bpix[yy+1])[xx+1] ) / 4;
break;
default:
/*
* et ici, un message d'erreur ?
*/
break;
}
}
}
demi->modified = 1;
return demi; /* demi is a pointer to an Image_Desc ! */
}
/*::------------------------------------------------------------------::*/