lib/art/art_rgb_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_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 rgb images
  30    over rgb pixel buffers. */
  31
  32 /**
  33  * art_rgb_affine: Affine transform source RGB image and composite.
  34  * @dst: Destination image RGB buffer.
  35  * @x0: Left coordinate of destination rectangle.
  36  * @y0: Top coordinate of destination rectangle.
  37  * @x1: Right coordinate of destination rectangle.
  38  * @y1: Bottom coordinate of destination rectangle.
  39  * @dst_rowstride: Rowstride of @dst buffer.
  40  * @src: Source image RGB buffer.
  41  * @src_width: Width of source image.
  42  * @src_height: Height of source image.
  43  * @src_rowstride: Rowstride of @src buffer.
  44  * @affine: Affine transform.
  45  * @level: Filter level.
  46  * @alphagamma: #ArtAlphaGamma for gamma-correcting the compositing.
  47  *
  48  * Affine transform the source image stored in @src, compositing over
  49  * the area of destination image @dst specified by the rectangle
  50  * (@x0, @y0) - (@x1, @y1). As usual in libart, the left and top edges
  51  * of this rectangle are included, and the right and bottom edges are
  52  * excluded.
  53  *
  54  * The @alphagamma parameter specifies that the alpha compositing be done
  55  * in a gamma-corrected color space. Since the source image is opaque RGB,
  56  * this argument only affects the edges. In the current implementation,
  57  * it is ignored.
  58  *
  59  * The @level parameter specifies the speed/quality tradeoff of the
  60  * image interpolation. Currently, only ART_FILTER_NEAREST is
  61  * implemented.
  62  **/
  63 void
  64 art_rgb_affine (art_u8 *dst, int x0, int y0, int x1, int y1, int dst_rowstride,
  65                 const art_u8 *src,
  66                 int src_width, int src_height, int src_rowstride,
  67                 const double affine[6],
  68                 ArtFilterLevel level,
  69                 ArtAlphaGamma *alphagamma)
  70 {
  71   /* Note: this is a slow implementation, and is missing all filter
  72      levels other than NEAREST. It is here for clarity of presentation
  73      and to establish the interface. */
  74   int x, y;
  75   double inv[6];
  76   art_u8 *dst_p, *dst_linestart;
  77   const art_u8 *src_p;
  78   ArtPoint pt, src_pt;
  79   int src_x, src_y;
  80   int run_x0, run_x1;
  81
  82   dst_linestart = dst;
  83   art_affine_invert (inv, affine);
  84   for (y = y0; y < y1; y++)
  85     {
  86       pt.y = y + 0.5;
  87       run_x0 = x0;
  88       run_x1 = x1;
  89       art_rgb_affine_run (&run_x0, &run_x1, y, src_width, src_height,
  90                           inv);
  91       dst_p = dst_linestart + (run_x0 - x0) * 3;
  92       for (x = run_x0; x < run_x1; x++)
  93         {
  94           pt.x = x + 0.5;
  95           art_affine_point (&src_pt, &pt, inv);
  96           src_x = floor (src_pt.x);
  97           src_y = floor (src_pt.y);
  98           src_p = src + (src_y * src_rowstride) + src_x * 3;
  99           dst_p[0] = src_p[0];
 100           dst_p[1] = src_p[1];
 101           dst_p[2] = src_p[2];
 102           dst_p += 3;
 103         }
 104       dst_linestart += dst_rowstride;
 105     }
 106 }