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
art_rgb_rgba_affine(art_u8 * dst,int x0,int y0,int x1,int y1,int dst_rowstride,const art_u8 * src,int src_width,int src_height,int src_rowstride,const double affine[6],ArtFilterLevel level,ArtAlphaGamma * alphagamma)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 }
143