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