sdl_zoom.c

   1 /*
   2  * SDL_zoom - surface scaling
   3  *
   4  * Copyright (c) 2009 Citrix Systems, Inc.
   5  *
   6  * Derived from: SDL_rotozoom,  LGPL (c) A. Schiffler from the SDL_gfx library.
   7  * Modifications by Stefano Stabellini.
   8  *
   9  * This work is licensed under the terms of the GNU GPL version 2.
  10  * See the COPYING file in the top-level directory.
  11  *
  12  */
  13
  14 #include "sdl_zoom.h"
  15 #include "osdep.h"
  16 #include <stdint.h>
  17 #include <stdio.h>
  18
  19 static int sdl_zoom_rgb16(SDL_Surface *src, SDL_Surface *dst, int smooth,
  20                           SDL_Rect *dst_rect);
  21 static int sdl_zoom_rgb32(SDL_Surface *src, SDL_Surface *dst, int smooth,
  22                           SDL_Rect *dst_rect);
  23
  24 #define BPP 32
  25 #include  "sdl_zoom_template.h"
  26 #undef BPP
  27 #define BPP 16
  28 #include  "sdl_zoom_template.h"
  29 #undef BPP
  30
  31 int sdl_zoom_blit(SDL_Surface *src_sfc, SDL_Surface *dst_sfc, int smooth,
  32                   SDL_Rect *in_rect)
  33 {
  34     SDL_Rect zoom, src_rect;
  35     int extra;
  36
  37     /* Grow the size of the modified rectangle to avoid edge artefacts */
  38     src_rect.x = (in_rect->x > 0) ? (in_rect->x - 1) : 0;
  39     src_rect.y = (in_rect->y > 0) ? (in_rect->y - 1) : 0;
  40
  41     src_rect.w = in_rect->w + 1;
  42     if (src_rect.x + src_rect.w > src_sfc->w)
  43         src_rect.w = src_sfc->w - src_rect.x;
  44
  45     src_rect.h = in_rect->h + 1;
  46     if (src_rect.y + src_rect.h > src_sfc->h)
  47         src_rect.h = src_sfc->h - src_rect.y;
  48
  49     /* (x,y) : round down */
  50     zoom.x = (int)(((float)(src_rect.x * dst_sfc->w)) / (float)(src_sfc->w));
  51     zoom.y = (int)(((float)(src_rect.y * dst_sfc->h)) / (float)(src_sfc->h));
  52
  53     /* (w,h) : round up */
  54     zoom.w = (int)( ((double)((src_rect.w * dst_sfc->w) + (src_sfc->w - 1))) /
  55                      (double)(src_sfc->w));
  56
  57     zoom.h = (int)( ((double)((src_rect.h * dst_sfc->h) + (src_sfc->h - 1))) /
  58                      (double)(src_sfc->h));
  59
  60     /* Account for any (x,y) rounding by adding one-source-pixel's worth
  61      * of destination pixels and then edge checking.
  62      */
  63
  64     extra = ((dst_sfc->w-1) / src_sfc->w) + 1;
  65
  66     if ((zoom.x + zoom.w) < (dst_sfc->w - extra))
  67         zoom.w += extra;
  68     else
  69         zoom.w = dst_sfc->w - zoom.x;
  70
  71     extra = ((dst_sfc->h-1) / src_sfc->h) + 1;
  72
  73     if ((zoom.y + zoom.h) < (dst_sfc->h - extra))
  74         zoom.h += extra;
  75     else
  76         zoom.h = dst_sfc->h - zoom.y;
  77
  78     /* The rectangle (zoom.x, zoom.y, zoom.w, zoom.h) is the area on the
  79      * destination surface that needs to be updated.
  80      */
  81     if (src_sfc->format->BitsPerPixel == 32)
  82         sdl_zoom_rgb32(src_sfc, dst_sfc, smooth, &zoom);
  83     else if (src_sfc->format->BitsPerPixel == 16)
  84         sdl_zoom_rgb16(src_sfc, dst_sfc, smooth, &zoom);
  85     else {
  86         fprintf(stderr, "pixel format not supported\n");
  87         return -1;
  88     }
  89
  90     /* Return the rectangle of the update to the caller */
  91     *in_rect = zoom;
  92
  93     return 0;
  94 }
  95