sixel_hls.c
1// sixel.c (part of mintty)
2// this function is derived from a part of graphics.c
3// in Xterm pl#310 originally written by Ross Combs.
4//
5// Copyright 2013,2014 by Ross Combs
6//
7// All Rights Reserved
8//
9// Permission is hereby granted, free of charge, to any person obtaining a
10// copy of this software and associated documentation files (the
11// "Software"), to deal in the Software without restriction, including
12// without limitation the rights to use, copy, modify, merge, publish,
13// distribute, sublicense, and/or sell copies of the Software, and to
14// permit persons to whom the Software is furnished to do so, subject to
15// the following conditions:
16//
17// The above copyright notice and this permission notice shall be included
18// in all copies or substantial portions of the Software.
19//
20// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
21// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
22// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
23// IN NO EVENT SHALL THE ABOVE LISTED COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
24// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
25// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
26// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
27//
28// Except as contained in this notice, the name(s) of the above copyright
29// holders shall not be used in advertising or otherwise to promote the
30// sale, use or other dealings in this Software without prior written
31// authorization.
32
33#define SIXEL_RGB(r, g, b) ((r) + ((g) << 8) + ((b) << 16) + (255 << 24))
34
35int
36hls_to_rgb(int hue, int lum, int sat)
37{
38 double hs = (hue + 240) % 360;
39 double hv = hs / 360.0;
40 double lv = lum / 100.0;
41 double sv = sat / 100.0;
42 double c, x, m, c2;
43 double r1, g1, b1;
44 int r, g, b;
45 int hpi;
46
47 if (sat == 0) {
48 r = g = b = lum * 255 / 100;
49 return SIXEL_RGB(r, g, b);
50 }
51
52 if ((c2 = ((2.0 * lv) - 1.0)) < 0.0) {
53 c2 = -c2;
54 }
55 c = (1.0 - c2) * sv;
56 hpi = (int) (hv * 6.0);
57 x = (hpi & 1) ? c : 0.0;
58 m = lv - 0.5 * c;
59
60 switch (hpi) {
61 case 0:
62 r1 = c;
63 g1 = x;
64 b1 = 0.0;
65 break;
66 case 1:
67 r1 = x;
68 g1 = c;
69 b1 = 0.0;
70 break;
71 case 2:
72 r1 = 0.0;
73 g1 = c;
74 b1 = x;
75 break;
76 case 3:
77 r1 = 0.0;
78 g1 = x;
79 b1 = c;
80 break;
81 case 4:
82 r1 = x;
83 g1 = 0.0;
84 b1 = c;
85 break;
86 case 5:
87 r1 = c;
88 g1 = 0.0;
89 b1 = x;
90 break;
91 default:
92 return SIXEL_RGB(255, 255, 255);
93 }
94
95 r = (int) ((r1 + m) * 100.0 + 0.5);
96 g = (int) ((g1 + m) * 100.0 + 0.5);
97 b = (int) ((b1 + m) * 100.0 + 0.5);
98
99 if (r < 0) {
100 r = 0;
101 } else if (r > 100) {
102 r = 100;
103 }
104 if (g < 0) {
105 g = 0;
106 } else if (g > 100) {
107 g = 100;
108 }
109 if (b < 0) {
110 b = 0;
111 } else if (b > 100) {
112 b = 100;
113 }
114 return SIXEL_RGB(r * 255 / 100, g * 255 / 100, b * 255 / 100);
115}
