Developer Documentation

HaltonColors.cc
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40 \*===========================================================================*/
41
42
43 //=============================================================================
44 //
45 // CLASS HaltonColors (by Marcel Campen)
46 //
47 //=============================================================================
48
49
50 //== INCLUDES =================================================================
51
52
53 #include <ACG/Utils/HaltonColors.hh>
54
55
56 //== NAMESPACES ===============================================================
57
58 namespace ACG {
59
60 //== CLASS IMPLEMENTATION =========================================================
61
62
63 HaltonColors::HaltonColors(int skip)
64 {
65 // skip first 250 sequence elements to lower discrepancy even further.
66 current[0] = skip;
67 current[1] = skip;
68 current[2] = skip;
69
70 // initialize prime bases for H,S,L. Especially the first should be small such that already
71 // small numbers of generated colors are distributed over the whole color circle.
72 bases[0] = 5;
73 bases[1] = 13;
74 bases[2] = 17;
75
76 inverse_bases[0] = 1.0f / bases[0];
77 inverse_bases[1] = 1.0f / bases[1];
78 inverse_bases[2] = 1.0f / bases[2];
79 }
80
81 float HaltonColors::halton(int index)
82 {
83 int base = bases[index];
84 float inverse_base = inverse_bases[index];
85 float H = 0;
86 float half = inverse_base;
87 int I = current[index];
88 current[index] += 1;
89 while (I > 0) {
90 int digit = I % base;
91 H = H + half * digit;
92 I = (int)(inverse_base * (I - digit));
93 half *= inverse_base;
94 }
95 return H;
96 }
97
98 float HaltonColors::random_interval(int index, float min, float max)
99 {
100 return halton(index) * (max - min) + min;
101 }
102
103 ACG::Vec4f HaltonColors::HSL2RGB(double h, double sl, double l)
104 {
105 double v;
106 double r, g, b;
107
108 r = l;
109 g = l;
110 b = l;
111
112 v = (l <= 0.5) ? (l * (1.0 + sl)) : (l + sl - l * sl);
113
114 if (v > 0) {
115 double m;
116 double sv;
117 int sextant;
118 double fract, vsf, mid1, mid2;
119
120 m = l + l - v;
121 sv = (v - m) / v;
122 h *= 6.0;
123 sextant = (int) h;
124 fract = h - sextant;
125 vsf = v * sv * fract;
126 mid1 = m + vsf;
127 mid2 = v - vsf;
128
129 switch (sextant) {
130 case 0:
131 r = v;
132 g = mid1;
133 b = m;
134 break;
135 case 1:
136 r = mid2;
137 g = v;
138 b = m;
139 break;
140 case 2:
141 r = m;
142 g = v;
143 b = mid1;
144 break;
145 case 3:
146 r = m;
147 g = mid2;
148 b = v;
149 break;
150 case 4:
151 r = mid1;
152 g = m;
153 b = v;
154 break;
155 case 5:
156 r = v;
157 g = m;
158 b = mid2;
159 break;
160 }
161 }
162
163 return Vec4f((float)r, (float)g, (float)b, 1.0f);
164 }
165
166 ACG::Vec4f HaltonColors::generateNextColor() {
167 float h = random_interval(0, 0.0f , 0.9f ); // 0.9 instead of 1.0 to suppress natural bias towards red
168 float s = random_interval(1, 0.40f, 0.80f); // saturation between 40% and 80%
169 float l = random_interval(2, 0.30f, 0.60f); // lightness between 30% and 60%
170 return HSL2RGB(h, s, l);
171 }
172
173 ACG::Vec4f HaltonColors::get_next_color()
174 {
175 return generateNextColor();
176 }
177
178
179 //=============================================================================
180 } // ACG namespace end
181 //=============================================================================
182 //=============================================================================
183
ACG
Namespace providing different geometric functions concerning angles.
Definition: BaseObjectData.hh:68
ACG::HaltonColors::generateNextColor
virtual ACG::Vec4f generateNextColor()
Generate the next color.
Definition: HaltonColors.cc:166
ACG::Vec4f
VectorT< float, 4 > Vec4f
Definition: VectorT.hh:138
ACG::HaltonColors::HaltonColors
HaltonColors(int skip=250)
Default constructor.
Definition: HaltonColors.cc:63
ACG::HaltonColors::get_next_color
ACG::Vec4f get_next_color()
Generate the next color (legacy method)
Definition: HaltonColors.cc:173
OpenMesh::VectorT
Definition: Vector11T.hh:83