lib/art/art_rgb_a_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_a_affine.h"
  22
  23 #include <math.h>
  24
  25 #include "art_affine.h"
  26 #include "art_point.h"
  27 #include "art_rgb_affine_private.h"
  28
  29 /* This module handles compositing of affine-transformed alpha only 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_a_affine: Affine transform source Alpha 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 alpha buffer.
  44  * @src_width: Width of source image.
  45  * @src_height: Height of source image.
  46  * @src_rowstride: Rowstride of @src buffer.
  47  * @rgb: RGB foreground color, in 0xRRGGBB.
  48  * @affine: Affine transform.
  49  * @level: Filter level.
  50  * @alphagamma: #ArtAlphaGamma for gamma-correcting the compositing.
  51  *
  52  * Affine transform the solid color rgb with alpha specified by the
  53  * source image stored in @src, compositing over the area of destination
  54  * image @dst specified by the rectangle (@x0, @y0) - (@x1, @y1).
  55  * As usual in libart, the left and top edges of this rectangle are
  56  * included, and the right and bottom edges are excluded.
  57  *
  58  * The @alphagamma parameter specifies that the alpha compositing be
  59  * done in a gamma-corrected color space. In the current
  60  * implementation, it is ignored.
  61  *
  62  * The @level parameter specifies the speed/quality tradeoff of the
  63  * image interpolation. Currently, only ART_FILTER_NEAREST is
  64  * implemented.
  65  **/
  66 void
  67 art_rgb_a_affine (art_u8 *dst,
  68                   int x0, int y0, int x1, int y1, int dst_rowstride,
  69                   const art_u8 *src,
  70                   int src_width, int src_height, int src_rowstride,
  71                   art_u32 rgb,
  72                   const double affine[6],
  73                   ArtFilterLevel level,
  74                   ArtAlphaGamma *alphagamma)
  75 {
  76   /* Note: this is a slow implementation, and is missing all filter
  77      levels other than NEAREST. It is here for clarity of presentation
  78      and to establish the interface. */
  79   int x, y;
  80   double inv[6];
  81   art_u8 *dst_p, *dst_linestart;
  82   const art_u8 *src_p;
  83   ArtPoint pt, src_pt;
  84   int src_x, src_y;
  85   int alpha;
  86   art_u8 bg_r, bg_g, bg_b;
  87   art_u8 fg_r, fg_g, fg_b;
  88   int tmp;
  89   int run_x0, run_x1;
  90   art_u8 r, g, b;
  91
  92   r = (rgb>>16)&0xff;
  93   g = (rgb>>8)&0xff;
  94   b = (rgb)&0xff;
  95
  96   dst_linestart = dst;
  97   art_affine_invert (inv, affine);
  98   for (y = y0; y < y1; y++)
  99     {
 100       pt.y = y + 0.5;
 101       run_x0 = x0;
 102       run_x1 = x1;
 103       art_rgb_affine_run (&run_x0, &run_x1, y, src_width, src_height,
 104                           inv);
 105       dst_p = dst_linestart + (run_x0 - x0) * 3;
 106       for (x = run_x0; x < run_x1; x++)
 107         {
 108           pt.x = x + 0.5;
 109           art_affine_point (&src_pt, &pt, inv);
 110           src_x = floor (src_pt.x);
 111           src_y = floor (src_pt.y);
 112           src_p = src + (src_y * src_rowstride) + src_x;
 113           if (src_x >= 0 && src_x < src_width &&
 114               src_y >= 0 && src_y < src_height)
 115             {
 116
 117           alpha = *src_p;
 118           if (alpha)
 119             {
 120               if (alpha == 255)
 121                 {
 122                   dst_p[0] = r;
 123                   dst_p[1] = g;
 124                   dst_p[2] = b;
 125                 }
 126               else
 127                 {
 128                   bg_r = dst_p[0];
 129                   bg_g = dst_p[1];
 130                   bg_b = dst_p[2];
 131
 132                   tmp = (r - bg_r) * alpha;
 133                   fg_r = bg_r + ((tmp + (tmp >> 8) + 0x80) >> 8);
 134                   tmp = (g - bg_g) * alpha;
 135                   fg_g = bg_g + ((tmp + (tmp >> 8) + 0x80) >> 8);
 136                   tmp = (b - bg_b) * alpha;
 137                   fg_b = bg_b + ((tmp + (tmp >> 8) + 0x80) >> 8);
 138
 139                   dst_p[0] = fg_r;
 140                   dst_p[1] = fg_g;
 141                   dst_p[2] = fg_b;
 142                 }
 143             }
 144             } else { dst_p[0] = 255; dst_p[1] = 0; dst_p[2] = 0; }
 145           dst_p += 3;
 146         }
 147       dst_linestart += dst_rowstride;
 148     }
 149 }