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 */
20 #include <math.h>
21 #include "art_misc.h"
22 #include "art_point.h"
23 #include "art_affine.h"
24 #include "art_rgb_affine_private.h"
25 #include "art_rgb_a_affine.h"
27 /* This module handles compositing of affine-transformed alpha only images
28 over rgb pixel buffers. */
30 /* Composite the source image over the destination image, applying the
31 affine transform. */
33 /**
34 * art_rgb_a_affine: Affine transform source Alpha image and composite.
35 * @dst: Destination image RGB buffer.
36 * @x0: Left coordinate of destination rectangle.
37 * @y0: Top coordinate of destination rectangle.
38 * @x1: Right coordinate of destination rectangle.
39 * @y1: Bottom coordinate of destination rectangle.
40 * @dst_rowstride: Rowstride of @dst buffer.
41 * @src: Source image alpha buffer.
42 * @src_width: Width of source image.
43 * @src_height: Height of source image.
44 * @src_rowstride: Rowstride of @src buffer.
45 * @rgb: RGB foreground color, in 0xRRGGBB.
46 * @affine: Affine transform.
47 * @level: Filter level.
48 * @alphagamma: #ArtAlphaGamma for gamma-correcting the compositing.
49 *
50 * Affine transform the solid color rgb with alpha specified by the
51 * source image stored in @src, compositing over the area of destination
52 * image @dst specified by the rectangle (@x0, @y0) - (@x1, @y1).
53 * As usual in libart, the left and top edges of this rectangle are
54 * included, and the right and bottom edges are excluded.
55 *
56 * The @alphagamma parameter specifies that the alpha compositing be
57 * done in a gamma-corrected color space. In the current
58 * implementation, it is ignored.
59 *
60 * The @level parameter specifies the speed/quality tradeoff of the
61 * image interpolation. Currently, only ART_FILTER_NEAREST is
62 * implemented.
63 **/
64 void
65 art_rgb_a_affine (art_u8 *dst,
66 int x0, int y0, int x1, int y1, int dst_rowstride,
67 const art_u8 *src,
68 int src_width, int src_height, int src_rowstride,
69 art_u32 rgb,
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 art_u8 r, g, b;
90 r = (rgb>>16)&0xff;
91 g = (rgb>>8)&0xff;
92 b = (rgb)&0xff;
94 dst_linestart = dst;
95 art_affine_invert (inv, affine);
96 for (y = y0; y < y1; y++)
97 {
98 pt.y = y + 0.5;
99 run_x0 = x0;
100 run_x1 = x1;
101 art_rgb_affine_run (&run_x0, &run_x1, y, src_width, src_height,
102 inv);
103 dst_p = dst_linestart + (run_x0 - x0) * 3;
104 for (x = run_x0; x < run_x1; x++)
105 {
106 pt.x = x + 0.5;
107 art_affine_point (&src_pt, &pt, inv);
108 src_x = floor (src_pt.x);
109 src_y = floor (src_pt.y);
110 src_p = src + (src_y * src_rowstride) + src_x;
111 if (src_x >= 0 && src_x < src_width &&
112 src_y >= 0 && src_y < src_height)
113 {
115 alpha = *src_p;
116 if (alpha)
117 {
118 if (alpha == 255)
119 {
120 dst_p[0] = r;
121 dst_p[1] = g;
122 dst_p[2] = b;
123 }
124 else
125 {
126 bg_r = dst_p[0];
127 bg_g = dst_p[1];
128 bg_b = dst_p[2];
130 tmp = (r - bg_r) * alpha;
131 fg_r = bg_r + ((tmp + (tmp >> 8) + 0x80) >> 8);
132 tmp = (g - bg_g) * alpha;
133 fg_g = bg_g + ((tmp + (tmp >> 8) + 0x80) >> 8);
134 tmp = (b - bg_b) * alpha;
135 fg_b = bg_b + ((tmp + (tmp >> 8) + 0x80) >> 8);
137 dst_p[0] = fg_r;
138 dst_p[1] = fg_g;
139 dst_p[2] = fg_b;
140 }
141 }
142 } else { dst_p[0] = 255; dst_p[1] = 0; dst_p[2] = 0; }
143 dst_p += 3;
144 }
145 dst_linestart += dst_rowstride;
146 }
147 }