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
  18 static int sdl_zoom_rgb16(SDL_Surface *src, SDL_Surface *dst, int smooth,
  19                           SDL_Rect *dst_rect);
  20 static int sdl_zoom_rgb32(SDL_Surface *src, SDL_Surface *dst, int smooth,
  21                           SDL_Rect *dst_rect);
  22
  23 #define BPP 32
  24 #include  "sdl_zoom_template.h"
  25 #undef BPP
  26 #define BPP 16
  27 #include  "sdl_zoom_template.h"
  28 #undef BPP
  29
  30 int sdl_zoom_blit(SDL_Surface *src_sfc, SDL_Surface *dst_sfc, int smooth,
  31                   SDL_Rect *in_rect)
  32 {
  33     SDL_Rect zoom, src_rect;
  34     int extra;
  35
  36     /* Grow the size of the modified rectangle to avoid edge artefacts */
  37     src_rect.x = (in_rect->x > 0) ? (in_rect->x - 1) : 0;
  38     src_rect.y = (in_rect->y > 0) ? (in_rect->y - 1) : 0;
  39
  40     src_rect.w = in_rect->w + 1;
  41     if (src_rect.x + src_rect.w > src_sfc->w)
  42         src_rect.w = src_sfc->w - src_rect.x;
  43
  44     src_rect.h = in_rect->h + 1;
  45     if (src_rect.y + src_rect.h > src_sfc->h)
  46         src_rect.h = src_sfc->h - src_rect.y;
  47
  48     /* (x,y) : round down */
  49     zoom.x = (int)(((float)(src_rect.x * dst_sfc->w)) / (float)(src_sfc->w));
  50     zoom.y = (int)(((float)(src_rect.y * dst_sfc->h)) / (float)(src_sfc->h));
  51
  52     /* (w,h) : round up */
  53     zoom.w = (int)( ((double)((src_rect.w * dst_sfc->w) + (src_sfc->w - 1))) /
  54                      (double)(src_sfc->w));
  55
  56     zoom.h = (int)( ((double)((src_rect.h * dst_sfc->h) + (src_sfc->h - 1))) /
  57                      (double)(src_sfc->h));
  58
  59     /* Account for any (x,y) rounding by adding one-source-pixel's worth
  60      * of destination pixels and then edge checking.
  61      */
  62
  63     extra = ((dst_sfc->w-1) / src_sfc->w) + 1;
  64
  65     if ((zoom.x + zoom.w) < (dst_sfc->w - extra))
  66         zoom.w += extra;
  67     else
  68         zoom.w = dst_sfc->w - zoom.x;
  69
  70     extra = ((dst_sfc->h-1) / src_sfc->h) + 1;
  71
  72     if ((zoom.y + zoom.h) < (dst_sfc->h - extra))
  73         zoom.h += extra;
  74     else
  75         zoom.h = dst_sfc->h - zoom.y;
  76
  77     /* The rectangle (zoom.x, zoom.y, zoom.w, zoom.h) is the area on the
  78      * destination surface that needs to be updated.
  79      */
  80     if (src_sfc->format->BitsPerPixel == 32)
  81         sdl_zoom_rgb32(src_sfc, dst_sfc, smooth, &zoom);
  82     else if (src_sfc->format->BitsPerPixel == 16)
  83         sdl_zoom_rgb16(src_sfc, dst_sfc, smooth, &zoom);
  84     else {
  85         fprintf(stderr, "pixel format not supported\n");
  86         return -1;
  87     }
  88
  89     /* Return the rectangle of the update to the caller */
  90     *in_rect = zoom;
  91
  92     return 0;
  93 }
  94