source/libs/cairo/cairo-src/src/cairo-color.c

   1 /* cairo - a vector graphics library with display and print output
   2  *
   3  * Copyright © 2002 University of Southern California
   4  * Copyright © 2005 Red Hat, Inc.
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it either under the terms of the GNU Lesser General Public
   8  * License version 2.1 as published by the Free Software Foundation
   9  * (the "LGPL") or, at your option, under the terms of the Mozilla
  10  * Public License Version 1.1 (the "MPL"). If you do not alter this
  11  * notice, a recipient may use your version of this file under either
  12  * the MPL or the LGPL.
  13  *
  14  * You should have received a copy of the LGPL along with this library
  15  * in the file COPYING-LGPL-2.1; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
  17  * You should have received a copy of the MPL along with this library
  18  * in the file COPYING-MPL-1.1
  19  *
  20  * The contents of this file are subject to the Mozilla Public License
  21  * Version 1.1 (the "License"); you may not use this file except in
  22  * compliance with the License. You may obtain a copy of the License at
  23  * http://www.mozilla.org/MPL/
  24  *
  25  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
  26  * OF ANY KIND, either express or implied. See the LGPL or the MPL for
  27  * the specific language governing rights and limitations.
  28  *
  29  * The Original Code is the cairo graphics library.
  30  *
  31  * The Initial Developer of the Original Code is University of Southern
  32  * California.
  33  *
  34  * Contributor(s):
  35  *      Carl D. Worth <cworth@cworth.org>
  36  */
  37
  38 #include "cairoint.h"
  39
  40 static cairo_color_t const cairo_color_white = {
  41     1.0,    1.0,    1.0,    1.0,
  42     0xffff, 0xffff, 0xffff, 0xffff
  43 };
  44
  45 static cairo_color_t const cairo_color_black = {
  46     0.0, 0.0, 0.0, 1.0,
  47     0x0, 0x0, 0x0, 0xffff
  48 };
  49
  50 static cairo_color_t const cairo_color_transparent = {
  51     0.0, 0.0, 0.0, 0.0,
  52     0x0, 0x0, 0x0, 0x0
  53 };
  54
  55 static cairo_color_t const cairo_color_magenta = {
  56     1.0,    0.0, 1.0,    1.0,
  57     0xffff, 0x0, 0xffff, 0xffff
  58 };
  59
  60 const cairo_color_t *
  61 _cairo_stock_color (cairo_stock_t stock)
  62 {
  63     switch (stock) {
  64     case CAIRO_STOCK_WHITE:
  65         return &cairo_color_white;
  66     case CAIRO_STOCK_BLACK:
  67         return &cairo_color_black;
  68     case CAIRO_STOCK_TRANSPARENT:
  69         return &cairo_color_transparent;
  70
  71     case CAIRO_STOCK_NUM_COLORS:
  72     default:
  73         ASSERT_NOT_REACHED;
  74         /* If the user can get here somehow, give a color that indicates a
  75          * problem. */
  76         return &cairo_color_magenta;
  77     }
  78 }
  79
  80 /* Convert a double in [0.0, 1.0] to an integer in [0, 65535]
  81  * The conversion is designed to choose the integer i such that
  82  * i / 65535.0 is as close as possible to the input value.
  83  */
  84 uint16_t
  85 _cairo_color_double_to_short (double d)
  86 {
  87     return d * 65535.0 + 0.5;
  88 }
  89
  90 static void
  91 _cairo_color_compute_shorts (cairo_color_t *color)
  92 {
  93     color->red_short   = _cairo_color_double_to_short (color->red   * color->alpha);
  94     color->green_short = _cairo_color_double_to_short (color->green * color->alpha);
  95     color->blue_short  = _cairo_color_double_to_short (color->blue  * color->alpha);
  96     color->alpha_short = _cairo_color_double_to_short (color->alpha);
  97 }
  98
  99 void
 100 _cairo_color_init_rgba (cairo_color_t *color,
 101                         double red, double green, double blue,
 102                         double alpha)
 103 {
 104     color->red   = red;
 105     color->green = green;
 106     color->blue  = blue;
 107     color->alpha = alpha;
 108
 109     _cairo_color_compute_shorts (color);
 110 }
 111
 112 void
 113 _cairo_color_multiply_alpha (cairo_color_t *color,
 114                              double         alpha)
 115 {
 116     color->alpha *= alpha;
 117
 118     _cairo_color_compute_shorts (color);
 119 }
 120
 121 void
 122 _cairo_color_get_rgba (cairo_color_t *color,
 123                        double        *red,
 124                        double        *green,
 125                        double        *blue,
 126                        double        *alpha)
 127 {
 128     *red   = color->red;
 129     *green = color->green;
 130     *blue  = color->blue;
 131     *alpha = color->alpha;
 132 }
 133
 134 void
 135 _cairo_color_get_rgba_premultiplied (cairo_color_t *color,
 136                                      double        *red,
 137                                      double        *green,
 138                                      double        *blue,
 139                                      double        *alpha)
 140 {
 141     *red   = color->red   * color->alpha;
 142     *green = color->green * color->alpha;
 143     *blue  = color->blue  * color->alpha;
 144     *alpha = color->alpha;
 145 }
 146
 147 /* NB: This function works both for unmultiplied and premultiplied colors */
 148 cairo_bool_t
 149 _cairo_color_equal (const cairo_color_t *color_a,
 150                     const cairo_color_t *color_b)
 151 {
 152     if (color_a == color_b)
 153         return TRUE;
 154
 155     if (color_a->alpha_short != color_b->alpha_short)
 156         return FALSE;
 157
 158     if (color_a->alpha_short == 0)
 159         return TRUE;
 160
 161     return color_a->red_short   == color_b->red_short   &&
 162            color_a->green_short == color_b->green_short &&
 163            color_a->blue_short  == color_b->blue_short;
 164 }
 165
 166 cairo_bool_t
 167 _cairo_color_stop_equal (const cairo_color_stop_t *color_a,
 168                          const cairo_color_stop_t *color_b)
 169 {
 170     if (color_a == color_b)
 171         return TRUE;
 172
 173     return color_a->alpha_short == color_b->alpha_short &&
 174            color_a->red_short   == color_b->red_short   &&
 175            color_a->green_short == color_b->green_short &&
 176            color_a->blue_short  == color_b->blue_short;
 177 }
 178
 179 cairo_content_t
 180 _cairo_color_get_content (const cairo_color_t *color)
 181 {
 182     if (CAIRO_COLOR_IS_OPAQUE (color))
 183         return CAIRO_CONTENT_COLOR;
 184
 185     if (color->red_short == 0 &&
 186         color->green_short == 0 &&
 187         color->blue_short == 0)
 188     {
 189         return CAIRO_CONTENT_ALPHA;
 190     }
 191
 192     return CAIRO_CONTENT_COLOR_ALPHA;
 193 }