wrlib/scale.c

   1 /* scale.c - image scaling
   2  *
   3  *  Raster graphics library
   4  *
   5  *  Copyright (c) 1997 Alfredo K. Kojima
   6  *
   7  *  This library is free software; you can redistribute it and/or
   8  *  modify it under the terms of the GNU Library General Public
   9  *  License as published by the Free Software Foundation; either
  10  *  version 2 of the License, or (at your option) any later version.
  11  *
  12  *  This library is distributed in the hope that it will be useful,
  13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  *  Library General Public License for more details.
  16  *
  17  *  You should have received a copy of the GNU Library General Public
  18  *  License along with this library; if not, write to the Free
  19  *  Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21
  22 #include <config.h>
  23
  24
  25 #include <stdlib.h>
  26 #include <stdio.h>
  27 #include <string.h>
  28 #include <X11/Xlib.h>
  29
  30 #include <assert.h>
  31
  32 #include "wraster.h"
  33
  34
  35 /*
  36  *----------------------------------------------------------------------
  37  * RScaleImage--
  38  *      Creates a scaled copy of an image.
  39  *
  40  * Returns:
  41  *      The new scaled image.
  42  *
  43  *----------------------------------------------------------------------
  44  */
  45 RImage*
  46 RScaleImage(RImage *image, unsigned new_width, unsigned new_height)
  47 {
  48     int ox;
  49     int px, py;
  50     register int x, y, t;
  51     int dx, dy;
  52     unsigned char *sr, *sg, *sb, *sa;
  53     unsigned char *dr, *dg, *db, *da;
  54     RImage *img;
  55
  56     assert(new_width >= 0 && new_height >= 0);
  57
  58     if (new_width == image->width && new_height == image->height)
  59         return RCloneImage(image);
  60
  61     img = RCreateImage(new_width, new_height, image->data[3]!=NULL);
  62
  63     if (!img)
  64       return NULL;
  65
  66     /* fixed point math idea taken from Imlib by
  67      * Carsten Haitzler (Rasterman) */
  68     dx = (image->width<<16)/new_width;
  69     dy = (image->height<<16)/new_height;
  70
  71     py = 0;
  72
  73     dr = img->data[0];
  74     dg = img->data[1];
  75     db = img->data[2];
  76     da = img->data[3];
  77
  78     if (image->data[3]!=NULL) {
  79         int ot;
  80         ot = -1;
  81         for (y=0; y<new_height; y++) {
  82             t = image->width*(py>>16);
  83
  84             sr = image->data[0]+t;
  85             sg = image->data[1]+t;
  86             sb = image->data[2]+t;
  87             sa = image->data[3]+t;
  88
  89             ot = t;
  90             ox = 0;
  91             px = 0;
  92             for (x=0; x<new_width; x++) {
  93                 px += dx;
  94
  95                 *(dr++) = *sr;
  96                 *(dg++) = *sg;
  97                 *(db++) = *sb;
  98                 *(da++) = *sa;
  99
 100                 t = (px - ox)>>16;
 101                 ox += t<<16;
 102
 103                 sr += t;
 104                 sg += t;
 105                 sb += t;
 106                 sa += t;
 107             }
 108             py += dy;
 109         }
 110     } else {
 111         int ot;
 112         ot = -1;
 113         for (y=0; y<new_height; y++) {
 114             t = image->width*(py>>16);
 115
 116             sr = image->data[0]+t;
 117             sg = image->data[1]+t;
 118             sb = image->data[2]+t;
 119
 120             ot = t;
 121             ox = 0;
 122             px = 0;
 123             for (x=0; x<new_width; x++) {
 124                 px += dx;
 125
 126                 *(dr++) = *sr;
 127                 *(dg++) = *sg;
 128                 *(db++) = *sb;
 129
 130                 t = (px-ox)>>16;
 131                 ox += t<<16;
 132
 133                 sr += t;
 134                 sg += t;
 135                 sb += t;
 136             }
 137             py += dy;
 138         }
 139     }
 140
 141     return img;
 142 }
 143