src/zoom_func.h

   1 /* $Id$ */
   2
   3 /*
   4  * This file is part of OpenTTD.
   5  * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
   6  * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
   7  * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
   8  */
   9
  10 /** @file zoom_func.h Functions related to zooming. */
  11
  12 #ifndef ZOOM_FUNC_H
  13 #define ZOOM_FUNC_H
  14
  15 #include "zoom_type.h"
  16
  17 /**
  18  * Scale by zoom level, usually shift left (when zoom > ZOOM_LVL_NORMAL)
  19  * When shifting right, value is rounded up
  20  * @param value value to shift
  21  * @param zoom  zoom level to shift to
  22  * @return shifted value
  23  */
  24 static inline int ScaleByZoom(int value, ZoomLevel zoom)
  25 {
  26         if (zoom == ZOOM_LVL_NORMAL) return value;
  27         int izoom = zoom - ZOOM_LVL_NORMAL;
  28         return (zoom > ZOOM_LVL_NORMAL) ? value << izoom : (value + (1 << -izoom) - 1) >> -izoom;
  29 }
  30
  31 /**
  32  * Scale by zoom level, usually shift right (when zoom > ZOOM_LVL_NORMAL)
  33  * When shifting right, value is rounded up
  34  * @param value value to shift
  35  * @param zoom  zoom level to shift to
  36  * @return shifted value
  37  */
  38 static inline int UnScaleByZoom(int value, ZoomLevel zoom)
  39 {
  40         if (zoom == ZOOM_LVL_NORMAL) return value;
  41         int izoom = zoom - ZOOM_LVL_NORMAL;
  42         return (zoom > ZOOM_LVL_NORMAL) ? (value + (1 << izoom) - 1) >> izoom : value << -izoom;
  43 }
  44
  45 /**
  46  * Scale by zoom level, usually shift left (when zoom > ZOOM_LVL_NORMAL)
  47  * @param value value to shift
  48  * @param zoom  zoom level to shift to
  49  * @return shifted value
  50  */
  51 static inline int ScaleByZoomLower(int value, ZoomLevel zoom)
  52 {
  53         if (zoom == ZOOM_LVL_NORMAL) return value;
  54         int izoom = zoom - ZOOM_LVL_NORMAL;
  55         return (zoom > ZOOM_LVL_NORMAL) ? value << izoom : value >> -izoom;
  56 }
  57
  58 /**
  59  * Scale by zoom level, usually shift right (when zoom > ZOOM_LVL_NORMAL)
  60  * @param value value to shift
  61  * @param zoom  zoom level to shift to
  62  * @return shifted value
  63  */
  64 static inline int UnScaleByZoomLower(int value, ZoomLevel zoom)
  65 {
  66         if (zoom == ZOOM_LVL_NORMAL) return value;
  67         int izoom = zoom - ZOOM_LVL_NORMAL;
  68         return (zoom > ZOOM_LVL_NORMAL) ? value >> izoom : value << -izoom;
  69 }
  70
  71 #endif /* ZOOM_FUNC_H */