lib/art/art_gray_svp.c

   1 /* Libart_LGPL - library of basic graphic primitives
   2  * Copyright (C) 1998 Raph Levien
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Library General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Library General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Library General Public
  15  * License along with this library; if not, write to the
  16  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17  * Boston, MA 02111-1307, USA.
  18  */
  19
  20 /* Render a sorted vector path into a graymap. */
  21
  22 #include "config.h"
  23 #include "art_gray_svp.h"
  24
  25 #include <string.h>     /* for memset */
  26 #include "art_misc.h"
  27
  28 #include "art_svp.h"
  29 #include "art_svp_render_aa.h"
  30
  31 typedef struct _ArtGraySVPData ArtGraySVPData;
  32
  33 struct _ArtGraySVPData {
  34   art_u8 *buf;
  35   int rowstride;
  36   int x0, x1;
  37 };
  38
  39 static void
  40 art_gray_svp_callback (void *callback_data, int y,
  41                        int start, ArtSVPRenderAAStep *steps, int n_steps)
  42 {
  43   ArtGraySVPData *data = (ArtGraySVPData *)callback_data;
  44   art_u8 *linebuf;
  45   int run_x0, run_x1;
  46   int running_sum = start;
  47   int x0, x1;
  48   int k;
  49
  50 #if 0
  51   printf ("start = %d", start);
  52   running_sum = start;
  53   for (k = 0; k < n_steps; k++)
  54     {
  55       running_sum += steps[k].delta;
  56       printf (" %d:%d", steps[k].x, running_sum >> 16);
  57     }
  58   printf ("\n");
  59 #endif
  60
  61   linebuf = data->buf;
  62   x0 = data->x0;
  63   x1 = data->x1;
  64
  65   if (n_steps > 0)
  66     {
  67       run_x1 = steps[0].x;
  68       if (run_x1 > x0)
  69         memset (linebuf, running_sum >> 16, run_x1 - x0);
  70
  71       for (k = 0; k < n_steps - 1; k++)
  72         {
  73           running_sum += steps[k].delta;
  74           run_x0 = run_x1;
  75           run_x1 = steps[k + 1].x;
  76           if (run_x1 > run_x0)
  77             memset (linebuf + run_x0 - x0, running_sum >> 16, run_x1 - run_x0);
  78         }
  79       running_sum += steps[k].delta;
  80       if (x1 > run_x1)
  81         memset (linebuf + run_x1 - x0, running_sum >> 16, x1 - run_x1);
  82     }
  83   else
  84     {
  85       memset (linebuf, running_sum >> 16, x1 - x0);
  86     }
  87
  88   data->buf += data->rowstride;
  89 }
  90
  91 /**
  92  * art_gray_svp_aa: Render the vector path into the bytemap.
  93  * @svp: The SVP to render.
  94  * @x0: The view window's left coord.
  95  * @y0: The view window's top coord.
  96  * @x1: The view window's right coord.
  97  * @y1: The view window's bottom coord.
  98  * @buf: The buffer where the bytemap is stored.
  99  * @rowstride: the rowstride for @buf.
 100  *
 101  * Each pixel gets a value proportional to the area within the pixel
 102  * overlapping the (filled) SVP. Pixel (x, y) is stored at:
 103  *
 104  *    @buf[(y - * @y0) * @rowstride + (x - @x0)]
 105  *
 106  * All pixels @x0 <= x < @x1, @y0 <= y < @y1 are generated. A
 107  * stored value of zero is no coverage, and a value of 255 is full
 108  * coverage. The area within the pixel (x, y) is the region covered
 109  * by [x..x+1] and [y..y+1].
 110  **/
 111 void
 112 art_gray_svp_aa (const ArtSVP *svp,
 113                  int x0, int y0, int x1, int y1,
 114                  art_u8 *buf, int rowstride)
 115 {
 116   ArtGraySVPData data;
 117
 118   data.buf = buf;
 119   data.rowstride = rowstride;
 120   data.x0 = x0;
 121   data.x1 = x1;
 122   art_svp_render_aa (svp, x0, y0, x1, y1, art_gray_svp_callback, &data);
 123 }