pixman-gradient-walker.c revision 1176bdada62cabc6ec4b0308a930e83b679d5d36
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 31void 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 53static void 54gradient_walker_reset (pixman_gradient_walker_t *walker, 55 pixman_fixed_48_16_t pos) 56{ 57 int32_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 172uint32_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} 203