source/libs/pixman/pixman-src/pixman/pixman-gradient-walker.c

   1 /*
   2  *
   3  * Copyright © 2000 Keith Packard, member of The XFree86 Project, Inc.
   4  *             2005 Lars Knoll & Zack Rusin, Trolltech
   5  *
   6  * Permission to use, copy, modify, distribute, and sell this software and its
   7  * documentation for any purpose is hereby granted without fee, provided that
   8  * the above copyright notice appear in all copies and that both that
   9  * copyright notice and this permission notice appear in supporting
  10  * documentation, and that the name of Keith Packard not be used in
  11  * advertising or publicity pertaining to distribution of the software without
  12  * specific, written prior permission.  Keith Packard makes no
  13  * representations about the suitability of this software for any purpose.  It
  14  * is provided "as is" without express or implied warranty.
  15  *
  16  * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS
  17  * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
  18  * FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY
  19  * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  20  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
  21  * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
  22  * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  23  * SOFTWARE.
  24  */
  25
  26 #ifdef HAVE_CONFIG_H
  27 #include <config.h>
  28 #endif
  29 #include "pixman-private.h"
  30
  31 void
  32 _pixman_gradient_walker_init (pixman_gradient_walker_t *walker,
  33                               gradient_t *              gradient,
  34                               pixman_repeat_t           repeat)
  35 {
  36     walker->num_stops = gradient->n_stops;
  37     walker->stops     = gradient->stops;
  38     walker->left_x    = 0;
  39     walker->right_x   = 0x10000;
  40     walker->a_s       = 0.0f;
  41     walker->a_b       = 0.0f;
  42     walker->r_s       = 0.0f;
  43     walker->r_b       = 0.0f;
  44     walker->g_s       = 0.0f;
  45     walker->g_b       = 0.0f;
  46     walker->b_s       = 0.0f;
  47     walker->b_b       = 0.0f;
  48     walker->repeat    = repeat;
  49
  50     walker->need_reset = TRUE;
  51 }
  52
  53 static void
  54 gradient_walker_reset (pixman_gradient_walker_t *walker,
  55                        pixman_fixed_48_16_t      pos)
  56 {
  57     int64_t x, left_x, right_x;
  58     pixman_color_t *left_c, *right_c;
  59     int n, count = walker->num_stops;
  60     pixman_gradient_stop_t *stops = walker->stops;
  61     float la, lr, lg, lb;
  62     float ra, rr, rg, rb;
  63     float lx, rx;
  64
  65     if (walker->repeat == PIXMAN_REPEAT_NORMAL)
  66     {
  67         x = (int32_t)pos & 0xffff;
  68     }
  69     else if (walker->repeat == PIXMAN_REPEAT_REFLECT)
  70     {
  71         x = (int32_t)pos & 0xffff;
  72         if ((int32_t)pos & 0x10000)
  73             x = 0x10000 - x;
  74     }
  75     else
  76     {
  77         x = pos;
  78     }
  79
  80     for (n = 0; n < count; n++)
  81     {
  82         if (x < stops[n].x)
  83             break;
  84     }
  85
  86     left_x =  stops[n - 1].x;
  87     left_c = &stops[n - 1].color;
  88
  89     right_x =  stops[n].x;
  90     right_c = &stops[n].color;
  91
  92     if (walker->repeat == PIXMAN_REPEAT_NORMAL)
  93     {
  94         left_x  += (pos - x);
  95         right_x += (pos - x);
  96     }
  97     else if (walker->repeat == PIXMAN_REPEAT_REFLECT)
  98     {
  99         if ((int32_t)pos & 0x10000)
 100         {
 101             pixman_color_t  *tmp_c;
 102             int32_t tmp_x;
 103
 104             tmp_x   = 0x10000 - right_x;
 105             right_x = 0x10000 - left_x;
 106             left_x  = tmp_x;
 107
 108             tmp_c   = right_c;
 109             right_c = left_c;
 110             left_c  = tmp_c;
 111
 112             x = 0x10000 - x;
 113         }
 114         left_x  += (pos - x);
 115         right_x += (pos - x);
 116     }
 117     else if (walker->repeat == PIXMAN_REPEAT_NONE)
 118     {
 119         if (n == 0)
 120             right_c = left_c;
 121         else if (n == count)
 122             left_c = right_c;
 123     }
 124
 125     /* The alpha channel is scaled to be in the [0, 255] interval,
 126      * and the red/green/blue channels are scaled to be in [0, 1].
 127      * This ensures that after premultiplication all channels will
 128      * be in the [0, 255] interval.
 129      */
 130     la = (left_c->alpha * (1.0f/257.0f));
 131     lr = (left_c->red * (1.0f/257.0f));
 132     lg = (left_c->green * (1.0f/257.0f));
 133     lb = (left_c->blue * (1.0f/257.0f));
 134
 135     ra = (right_c->alpha * (1.0f/257.0f));
 136     rr = (right_c->red * (1.0f/257.0f));
 137     rg = (right_c->green * (1.0f/257.0f));
 138     rb = (right_c->blue * (1.0f/257.0f));
 139
 140     lx = left_x * (1.0f/65536.0f);
 141     rx = right_x * (1.0f/65536.0f);
 142
 143     if (FLOAT_IS_ZERO (rx - lx) || left_x == INT32_MIN || right_x == INT32_MAX)
 144     {
 145         walker->a_s = walker->r_s = walker->g_s = walker->b_s = 0.0f;
 146         walker->a_b = (la + ra) / 2.0f;
 147         walker->r_b = (lr + rr) / 510.0f;
 148         walker->g_b = (lg + rg) / 510.0f;
 149         walker->b_b = (lb + rb) / 510.0f;
 150     }
 151     else
 152     {
 153         float w_rec = 1.0f / (rx - lx);
 154
 155         walker->a_b = (la * rx - ra * lx) * w_rec;
 156         walker->r_b = (lr * rx - rr * lx) * w_rec * (1.0f/255.0f);
 157         walker->g_b = (lg * rx - rg * lx) * w_rec * (1.0f/255.0f);
 158         walker->b_b = (lb * rx - rb * lx) * w_rec * (1.0f/255.0f);
 159
 160         walker->a_s = (ra - la) * w_rec;
 161         walker->r_s = (rr - lr) * w_rec * (1.0f/255.0f);
 162         walker->g_s = (rg - lg) * w_rec * (1.0f/255.0f);
 163         walker->b_s = (rb - lb) * w_rec * (1.0f/255.0f);
 164     }
 165
 166     walker->left_x = left_x;
 167     walker->right_x = right_x;
 168
 169     walker->need_reset = FALSE;
 170 }
 171
 172 uint32_t
 173 _pixman_gradient_walker_pixel (pixman_gradient_walker_t *walker,
 174                                pixman_fixed_48_16_t      x)
 175 {
 176     float a, r, g, b;
 177     uint8_t a8, r8, g8, b8;
 178     uint32_t v;
 179     float y;
 180
 181     if (walker->need_reset || x < walker->left_x || x >= walker->right_x)
 182         gradient_walker_reset (walker, x);
 183
 184     y = x * (1.0f / 65536.0f);
 185
 186     a = walker->a_s * y + walker->a_b;
 187     r = a * (walker->r_s * y + walker->r_b);
 188     g = a * (walker->g_s * y + walker->g_b);
 189     b = a * (walker->b_s * y + walker->b_b);
 190
 191     a8 = a + 0.5f;
 192     r8 = r + 0.5f;
 193     g8 = g + 0.5f;
 194     b8 = b + 0.5f;
 195
 196     v = ((a8 << 24) & 0xff000000) |
 197         ((r8 << 16) & 0x00ff0000) |
 198         ((g8 <<  8) & 0x0000ff00) |
 199         ((b8 >>  0) & 0x000000ff);
 200
 201     return v;
 202 }