lib/art/art_rgb_rgba_affine.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 #include "config.h"
  21 #include "art_rgb_rgba_affine.h"
  22
  23 #include <math.h>
  24 #include "art_misc.h"
  25 #include "art_point.h"
  26 #include "art_affine.h"
  27 #include "art_rgb_affine_private.h"
  28
  29 /* This module handles compositing of affine-transformed rgba images
  30    over rgb pixel buffers. */
  31
  32 /* Composite the source image over the destination image, applying the
  33    affine transform. */
  34
  35 /**
  36  * art_rgb_rgba_affine: Affine transform source RGBA image and composite.
  37  * @dst: Destination image RGB buffer.
  38  * @x0: Left coordinate of destination rectangle.
  39  * @y0: Top coordinate of destination rectangle.
  40  * @x1: Right coordinate of destination rectangle.
  41  * @y1: Bottom coordinate of destination rectangle.
  42  * @dst_rowstride: Rowstride of @dst buffer.
  43  * @src: Source image RGBA buffer.
  44  * @src_width: Width of source image.
  45  * @src_height: Height of source image.
  46  * @src_rowstride: Rowstride of @src buffer.
  47  * @affine: Affine transform.
  48  * @level: Filter level.
  49  * @alphagamma: #ArtAlphaGamma for gamma-correcting the compositing.
  50  *
  51  * Affine transform the source image stored in @src, compositing over
  52  * the area of destination image @dst specified by the rectangle
  53  * (@x0, @y0) - (@x1, @y1). As usual in libart, the left and top edges
  54  * of this rectangle are included, and the right and bottom edges are
  55  * excluded.
  56  *
  57  * The @alphagamma parameter specifies that the alpha compositing be
  58  * done in a gamma-corrected color space. In the current
  59  * implementation, it is ignored.
  60  *
  61  * The @level parameter specifies the speed/quality tradeoff of the
  62  * image interpolation. Currently, only ART_FILTER_NEAREST is
  63  * implemented.
  64  **/
  65 void
  66 art_rgb_rgba_affine (art_u8 *dst,
  67                      int x0, int y0, int x1, int y1, int dst_rowstride,
  68                      const art_u8 *src,
  69                      int src_width, int src_height, int src_rowstride,
  70                      const double affine[6],
  71                      ArtFilterLevel level,
  72                      ArtAlphaGamma *alphagamma)
  73 {
  74   /* Note: this is a slow implementation, and is missing all filter
  75      levels other than NEAREST. It is here for clarity of presentation
  76      and to establish the interface. */
  77   int x, y;
  78   double inv[6];
  79   art_u8 *dst_p, *dst_linestart;
  80   const art_u8 *src_p;
  81   ArtPoint pt, src_pt;
  82   int src_x, src_y;
  83   int alpha;
  84   art_u8 bg_r, bg_g, bg_b;
  85   art_u8 fg_r, fg_g, fg_b;
  86   int tmp;
  87   int run_x0, run_x1;
  88
  89   dst_linestart = dst;
  90   art_affine_invert (inv, affine);
  91   for (y = y0; y < y1; y++)
  92     {
  93       pt.y = y + 0.5;
  94       run_x0 = x0;
  95       run_x1 = x1;
  96       art_rgb_affine_run (&run_x0, &run_x1, y, src_width, src_height,
  97                           inv);
  98       dst_p = dst_linestart + (run_x0 - x0) * 3;
  99       for (x = run_x0; x < run_x1; x++)
 100         {
 101           pt.x = x + 0.5;
 102           art_affine_point (&src_pt, &pt, inv);
 103           src_x = floor (src_pt.x);
 104           src_y = floor (src_pt.y);
 105           src_p = src + (src_y * src_rowstride) + src_x * 4;
 106           if (src_x >= 0 && src_x < src_width &&
 107               src_y >= 0 && src_y < src_height)
 108             {
 109
 110           alpha = src_p[3];
 111           if (alpha)
 112             {
 113               if (alpha == 255)
 114                 {
 115                   dst_p[0] = src_p[0];
 116                   dst_p[1] = src_p[1];
 117                   dst_p[2] = src_p[2];
 118                 }
 119               else
 120                 {
 121                   bg_r = dst_p[0];
 122                   bg_g = dst_p[1];
 123                   bg_b = dst_p[2];
 124
 125                   tmp = (src_p[0] - bg_r) * alpha;
 126                   fg_r = bg_r + ((tmp + (tmp >> 8) + 0x80) >> 8);
 127                   tmp = (src_p[1] - bg_g) * alpha;
 128                   fg_g = bg_g + ((tmp + (tmp >> 8) + 0x80) >> 8);
 129                   tmp = (src_p[2] - bg_b) * alpha;
 130                   fg_b = bg_b + ((tmp + (tmp >> 8) + 0x80) >> 8);
 131
 132                   dst_p[0] = fg_r;
 133                   dst_p[1] = fg_g;
 134                   dst_p[2] = fg_b;
 135                 }
 136             }
 137             } else { dst_p[0] = 255; dst_p[1] = 0; dst_p[2] = 0; }
 138           dst_p += 3;
 139         }
 140       dst_linestart += dst_rowstride;
 141     }
 142 }