ColorUtils.java revision e1dfa4c5019de5823d05ea09417f28e55e7430fa 
1/*
2 * Copyright 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *       http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.support.v7.graphics;
18
19import android.graphics.Color;
20
21final class ColorUtils {
22
23    private ColorUtils() {}
24
25    /**
26     * @return luma value according to to XYZ color space in the range 0.0 - 1.0
27     */
28    static float calculateXyzLuma(int color) {
29        return (0.2126f * Color.red(color) +
30                0.7152f * Color.green(color) +
31                0.0722f * Color.blue(color)) / 255f;
32    }
33
34    static float calculateContrast(int color1, int color2) {
35        return Math.abs(ColorUtils.calculateXyzLuma(color1) - ColorUtils.calculateXyzLuma(color2));
36    }
37
38    static void RGBtoHSL(int r, int g, int b, float[] hsl) {
39        final float rf = r / 255f;
40        final float gf = g / 255f;
41        final float bf = b / 255f;
42
43        final float max = Math.max(rf, Math.max(gf, bf));
44        final float min = Math.min(rf, Math.min(gf, bf));
45        final float deltaMaxMin = max - min;
46
47        float h, s;
48        float l = (max + min) / 2f;
49
50        if (max == min) {
51            // Monochromatic
52            h = s = 0f;
53        } else {
54            if (max == rf) {
55                h = ((gf - bf) / deltaMaxMin) % 6f;
56            } else if (max == gf) {
57                h = ((bf - rf) / deltaMaxMin) + 2f;
58            } else {
59                h = ((rf - gf) / deltaMaxMin) + 4f;
60            }
61
62            s =  deltaMaxMin / (1f - Math.abs(2f * l - 1f));
63        }
64
65        hsl[0] = (h * 60f) % 360f;
66        hsl[1] = s;
67        hsl[2] = l;
68    }
69
70    static int HSLtoRGB (float[] hsl) {
71        final float h = hsl[0];
72        final float s = hsl[1];
73        final float l = hsl[2];
74
75        final float c = (1f - Math.abs(2 * l - 1f)) * s;
76        final float m = l - 0.5f * c;
77        final float x = c * (1f - Math.abs((h / 60f % 2f) - 1f));
78
79        final int hueSegment = (int) h / 60;
80
81        int r = 0, g = 0, b = 0;
82
83        switch (hueSegment) {
84            case 0:
85                r = Math.round(255 * (c + m));
86                g = Math.round(255 * (x + m));
87                b = Math.round(255 * m);
88                break;
89            case 1:
90                r = Math.round(255 * (x + m));
91                g = Math.round(255 * (c + m));
92                b = Math.round(255 * m);
93                break;
94            case 2:
95                r = Math.round(255 * m);
96                g = Math.round(255 * (c + m));
97                b = Math.round(255 * (x + m));
98                break;
99            case 3:
100                r = Math.round(255 * m);
101                g = Math.round(255 * (x + m));
102                b = Math.round(255 * (c + m));
103                break;
104            case 4:
105                r = Math.round(255 * (x + m));
106                g = Math.round(255 * m);
107                b = Math.round(255 * (c + m));
108                break;
109            case 5:
110            case 6:
111                r = Math.round(255 * (c + m));
112                g = Math.round(255 * m);
113                b = Math.round(255 * (x + m));
114                break;
115        }
116
117        r = Math.max(0, Math.min(255, r));
118        g = Math.max(0, Math.min(255, g));
119        b = Math.max(0, Math.min(255, b));
120
121        return Color.rgb(r, g, b);
122    }
123
124}
125