summaryrefslogtreecommitdiffstats
path: root/gfx/cairo/libpixman/src/pixman-gradient-walker.c
blob: fb7f401dac5c5f194236491911c203a806a22910 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
/*
 *
 * Copyright © 2000 Keith Packard, member of The XFree86 Project, Inc.
 *             2005 Lars Knoll & Zack Rusin, Trolltech
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that
 * copyright notice and this permission notice appear in supporting
 * documentation, and that the name of Keith Packard not be used in
 * advertising or publicity pertaining to distribution of the software without
 * specific, written prior permission.  Keith Packard makes no
 * representations about the suitability of this software for any purpose.  It
 * is provided "as is" without express or implied warranty.
 *
 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS
 * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include "pixman-private.h"

void
_pixman_gradient_walker_init (pixman_gradient_walker_t *walker,
                              gradient_t *              gradient,
                              pixman_repeat_t		repeat)
{
    walker->num_stops = gradient->n_stops;
    walker->stops     = gradient->stops;
    walker->left_x    = 0;
    walker->right_x   = 0x10000;
    walker->a_s       = 0.0f;
    walker->a_b       = 0.0f;
    walker->r_s       = 0.0f;
    walker->r_b       = 0.0f;
    walker->g_s       = 0.0f;
    walker->g_b       = 0.0f;
    walker->b_s       = 0.0f;
    walker->b_b       = 0.0f;
    walker->repeat    = repeat;

    walker->need_reset = TRUE;
}

static void
gradient_walker_reset (pixman_gradient_walker_t *walker,
		       pixman_fixed_48_16_t      pos)
{
    int64_t x, left_x, right_x;
    pixman_color_t *left_c, *right_c;
    int n, count = walker->num_stops;
    pixman_gradient_stop_t *stops = walker->stops;
    float la, lr, lg, lb;
    float ra, rr, rg, rb;
    float lx, rx;

    if (walker->repeat == PIXMAN_REPEAT_NORMAL)
    {
	x = (int32_t)pos & 0xffff;
    }
    else if (walker->repeat == PIXMAN_REPEAT_REFLECT)
    {
	x = (int32_t)pos & 0xffff;
	if ((int32_t)pos & 0x10000)
	    x = 0x10000 - x;
    }
    else
    {
	x = pos;
    }
    
    for (n = 0; n < count; n++)
    {
	if (x < stops[n].x)
	    break;
    }
    
    left_x =  stops[n - 1].x;
    left_c = &stops[n - 1].color;
    
    right_x =  stops[n].x;
    right_c = &stops[n].color;

    if (walker->repeat == PIXMAN_REPEAT_NORMAL)
    {
	left_x  += (pos - x);
	right_x += (pos - x);
    }
    else if (walker->repeat == PIXMAN_REPEAT_REFLECT)
    {
	if ((int32_t)pos & 0x10000)
	{
	    pixman_color_t  *tmp_c;
	    int32_t tmp_x;

	    tmp_x   = 0x10000 - right_x;
	    right_x = 0x10000 - left_x;
	    left_x  = tmp_x;

	    tmp_c   = right_c;
	    right_c = left_c;
	    left_c  = tmp_c;

	    x = 0x10000 - x;
	}
	left_x  += (pos - x);
	right_x += (pos - x);
    }
    else if (walker->repeat == PIXMAN_REPEAT_NONE)
    {
	if (n == 0)
	    right_c = left_c;
	else if (n == count)
	    left_c = right_c;
    }

    /* The alpha/red/green/blue channels are scaled to be in [0, 1].
     * This ensures that after premultiplication all channels will
     * be in the [0, 1] interval.
     */
    la = (left_c->alpha * (1.0f/257.0f));
    lr = (left_c->red * (1.0f/257.0f));
    lg = (left_c->green * (1.0f/257.0f));
    lb = (left_c->blue * (1.0f/257.0f));

    ra = (right_c->alpha * (1.0f/257.0f));
    rr = (right_c->red * (1.0f/257.0f));
    rg = (right_c->green * (1.0f/257.0f));
    rb = (right_c->blue * (1.0f/257.0f));
    
    lx = left_x * (1.0f/65536.0f);
    rx = right_x * (1.0f/65536.0f);
    
    if (FLOAT_IS_ZERO (rx - lx) || left_x == INT32_MIN || right_x == INT32_MAX)
    {
	walker->a_s = walker->r_s = walker->g_s = walker->b_s = 0.0f;
	walker->a_b = (la + ra) / 510.0f;
	walker->r_b = (lr + rr) / 510.0f;
	walker->g_b = (lg + rg) / 510.0f;
	walker->b_b = (lb + rb) / 510.0f;
    }
    else
    {
	float w_rec = 1.0f / (rx - lx);

	walker->a_b = (la * rx - ra * lx) * w_rec * (1.0f/255.0f);
	walker->r_b = (lr * rx - rr * lx) * w_rec * (1.0f/255.0f);
	walker->g_b = (lg * rx - rg * lx) * w_rec * (1.0f/255.0f);
	walker->b_b = (lb * rx - rb * lx) * w_rec * (1.0f/255.0f);

	walker->a_s = (ra - la) * w_rec * (1.0f/255.0f);
	walker->r_s = (rr - lr) * w_rec * (1.0f/255.0f);
	walker->g_s = (rg - lg) * w_rec * (1.0f/255.0f);
	walker->b_s = (rb - lb) * w_rec * (1.0f/255.0f);
    }
   
    walker->left_x = left_x;
    walker->right_x = right_x;

    walker->need_reset = FALSE;
}

static argb_t
pixman_gradient_walker_pixel_float (pixman_gradient_walker_t *walker,
				    pixman_fixed_48_16_t      x)
{
    argb_t f;
    float y;

    if (walker->need_reset || x < walker->left_x || x >= walker->right_x)
	gradient_walker_reset (walker, x);

    y = x * (1.0f / 65536.0f);

    f.a = walker->a_s * y + walker->a_b;
    f.r = f.a * (walker->r_s * y + walker->r_b);
    f.g = f.a * (walker->g_s * y + walker->g_b);
    f.b = f.a * (walker->b_s * y + walker->b_b);

    return f;
}

static uint32_t
pixman_gradient_walker_pixel_32 (pixman_gradient_walker_t *walker,
				 pixman_fixed_48_16_t      x)
{
    argb_t f;
    float y;

    if (walker->need_reset || x < walker->left_x || x >= walker->right_x)
	gradient_walker_reset (walker, x);

    y = x * (1.0f / 65536.0f);

    /* Instead of [0...1] for ARGB, we want [0...255],
     * multiply alpha with 255 and the color channels
     * also get multiplied by the alpha multiplier.
     *
     * We don't use pixman_contract_from_float because it causes a 2x
     * slowdown to do so, and the values are already normalized,
     * so we don't have to worry about values < 0.f or > 1.f
     */
    f.a = 255.f * (walker->a_s * y + walker->a_b);
    f.r = f.a * (walker->r_s * y + walker->r_b);
    f.g = f.a * (walker->g_s * y + walker->g_b);
    f.b = f.a * (walker->b_s * y + walker->b_b);

    return (((uint32_t)(f.a + .5f) << 24) & 0xff000000) |
           (((uint32_t)(f.r + .5f) << 16) & 0x00ff0000) |
           (((uint32_t)(f.g + .5f) <<  8) & 0x0000ff00) |
           (((uint32_t)(f.b + .5f) >>  0) & 0x000000ff);
}

void
_pixman_gradient_walker_write_narrow (pixman_gradient_walker_t *walker,
				      pixman_fixed_48_16_t      x,
				      uint32_t                 *buffer)
{
    *buffer = pixman_gradient_walker_pixel_32 (walker, x);
}

void
_pixman_gradient_walker_write_wide (pixman_gradient_walker_t *walker,
				    pixman_fixed_48_16_t      x,
				    uint32_t                 *buffer)
{
    *(argb_t *)buffer = pixman_gradient_walker_pixel_float (walker, x);
}

void
_pixman_gradient_walker_fill_narrow (pixman_gradient_walker_t *walker,
				     pixman_fixed_48_16_t      x,
				     uint32_t                 *buffer,
				     uint32_t                 *end)
{
    register uint32_t color;

    color = pixman_gradient_walker_pixel_32 (walker, x);
    while (buffer < end)
	*buffer++ = color;
}

void
_pixman_gradient_walker_fill_wide (pixman_gradient_walker_t *walker,
				   pixman_fixed_48_16_t      x,
				   uint32_t                 *buffer,
				   uint32_t                 *end)
{
    register argb_t color;
    argb_t *buffer_wide = (argb_t *)buffer;
    argb_t *end_wide    = (argb_t *)end;

    color = pixman_gradient_walker_pixel_float (walker, x);
    while (buffer_wide < end_wide)
	*buffer_wide++ = color;
}