1 /*
2  * Copyright (C) 2017 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 
17 package com.android.launcher3.graphics;
18 
19 import android.app.Notification;
20 import android.content.Context;
21 import android.graphics.Color;
22 import android.util.Log;
23 
24 import androidx.core.graphics.ColorUtils;
25 
26 import com.android.launcher3.R;
27 import com.android.launcher3.util.Themes;
28 
29 /**
30  * Contains colors based on the dominant color of an icon.
31  */
32 public class IconPalette {
33 
34     private static final boolean DEBUG = false;
35     private static final String TAG = "IconPalette";
36 
37     private static final float MIN_PRELOAD_COLOR_SATURATION = 0.2f;
38     private static final float MIN_PRELOAD_COLOR_LIGHTNESS = 0.6f;
39 
40     /**
41      * Returns a color suitable for the progress bar color of preload icon.
42      */
getPreloadProgressColor(Context context, int dominantColor)43     public static int getPreloadProgressColor(Context context, int dominantColor) {
44         int result = dominantColor;
45 
46         // Make sure that the dominant color has enough saturation to be visible properly.
47         float[] hsv = new float[3];
48         Color.colorToHSV(result, hsv);
49         if (hsv[1] < MIN_PRELOAD_COLOR_SATURATION) {
50             result = Themes.getColorAccent(context);
51         } else {
52             hsv[2] = Math.max(MIN_PRELOAD_COLOR_LIGHTNESS, hsv[2]);
53             result = Color.HSVToColor(hsv);
54         }
55         return result;
56     }
57 
58     /**
59      * Resolves a color such that it has enough contrast to be used as the
60      * color of an icon or text on the given background color.
61      *
62      * @return a color of the same hue with enough contrast against the background.
63      *
64      * This was copied from com.android.internal.util.NotificationColorUtil.
65      */
resolveContrastColor(Context context, int color, int background)66     public static int resolveContrastColor(Context context, int color, int background) {
67         final int resolvedColor = resolveColor(context, color);
68 
69         int contrastingColor = ensureTextContrast(resolvedColor, background);
70 
71         if (contrastingColor != resolvedColor) {
72             if (DEBUG){
73                 Log.w(TAG, String.format(
74                         "Enhanced contrast of notification for %s " +
75                                 "%s (over background) by changing #%s to %s",
76                         context.getPackageName(),
77                         contrastChange(resolvedColor, contrastingColor, background),
78                         Integer.toHexString(resolvedColor), Integer.toHexString(contrastingColor)));
79             }
80         }
81         return contrastingColor;
82     }
83 
84     /**
85      * Resolves {@param color} to an actual color if it is {@link Notification#COLOR_DEFAULT}
86      *
87      * This was copied from com.android.internal.util.NotificationColorUtil.
88      */
resolveColor(Context context, int color)89     private static int resolveColor(Context context, int color) {
90         if (color == Notification.COLOR_DEFAULT) {
91             return context.getColor(R.color.notification_icon_default_color);
92         }
93         return color;
94     }
95 
96     /** For debugging. This was copied from com.android.internal.util.NotificationColorUtil. */
contrastChange(int colorOld, int colorNew, int bg)97     private static String contrastChange(int colorOld, int colorNew, int bg) {
98         return String.format("from %.2f:1 to %.2f:1",
99                 ColorUtils.calculateContrast(colorOld, bg),
100                 ColorUtils.calculateContrast(colorNew, bg));
101     }
102 
103     /**
104      * Finds a text color with sufficient contrast over bg that has the same hue as the original
105      * color.
106      *
107      * This was copied from com.android.internal.util.NotificationColorUtil.
108      */
ensureTextContrast(int color, int bg)109     private static int ensureTextContrast(int color, int bg) {
110         return findContrastColor(color, bg, 4.5);
111     }
112     /**
113      * Finds a suitable color such that there's enough contrast.
114      *
115      * @param fg the color to start searching from.
116      * @param bg the color to ensure contrast against.
117      * @param minRatio the minimum contrast ratio required.
118      * @return a color with the same hue as {@param color}, potentially darkened to meet the
119      *          contrast ratio.
120      *
121      * This was copied from com.android.internal.util.NotificationColorUtil.
122      */
findContrastColor(int fg, int bg, double minRatio)123     private static int findContrastColor(int fg, int bg, double minRatio) {
124         if (ColorUtils.calculateContrast(fg, bg) >= minRatio) {
125             return fg;
126         }
127 
128         double[] lab = new double[3];
129         ColorUtils.colorToLAB(bg, lab);
130         double bgL = lab[0];
131         ColorUtils.colorToLAB(fg, lab);
132         double fgL = lab[0];
133         boolean isBgDark = bgL < 50;
134 
135         double low = isBgDark ? fgL : 0, high = isBgDark ? 100 : fgL;
136         final double a = lab[1], b = lab[2];
137         for (int i = 0; i < 15 && high - low > 0.00001; i++) {
138             final double l = (low + high) / 2;
139             fg = ColorUtils.LABToColor(l, a, b);
140             if (ColorUtils.calculateContrast(fg, bg) > minRatio) {
141                 if (isBgDark) high = l; else low = l;
142             } else {
143                 if (isBgDark) low = l; else high = l;
144             }
145         }
146         return ColorUtils.LABToColor(low, a, b);
147     }
148 }
149