com/android/systemui/shared/recents/utilities/Utilities.java

/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.systemui.shared.recents.utilities;

import android.graphics.Color;
import android.os.Handler;
import android.os.Message;

/* Common code */
public class Utilities {

    /**
     * Posts a runnable on a handler at the front of the queue ignoring any sync barriers.
     */
    public static void postAtFrontOfQueueAsynchronously(Handler h, Runnable r) {
        Message msg = h.obtainMessage().setCallback(r);
        h.sendMessageAtFrontOfQueue(msg);
    }

    /** Calculates the constrast between two colors, using the algorithm provided by the WCAG v2. */
    public static float computeContrastBetweenColors(int bg, int fg) {
        float bgR = Color.red(bg) / 255f;
        float bgG = Color.green(bg) / 255f;
        float bgB = Color.blue(bg) / 255f;
        bgR = (bgR < 0.03928f) ? bgR / 12.92f : (float) Math.pow((bgR + 0.055f) / 1.055f, 2.4f);
        bgG = (bgG < 0.03928f) ? bgG / 12.92f : (float) Math.pow((bgG + 0.055f) / 1.055f, 2.4f);
        bgB = (bgB < 0.03928f) ? bgB / 12.92f : (float) Math.pow((bgB + 0.055f) / 1.055f, 2.4f);
        float bgL = 0.2126f * bgR + 0.7152f * bgG + 0.0722f * bgB;

        float fgR = Color.red(fg) / 255f;
        float fgG = Color.green(fg) / 255f;
        float fgB = Color.blue(fg) / 255f;
        fgR = (fgR < 0.03928f) ? fgR / 12.92f : (float) Math.pow((fgR + 0.055f) / 1.055f, 2.4f);
        fgG = (fgG < 0.03928f) ? fgG / 12.92f : (float) Math.pow((fgG + 0.055f) / 1.055f, 2.4f);
        fgB = (fgB < 0.03928f) ? fgB / 12.92f : (float) Math.pow((fgB + 0.055f) / 1.055f, 2.4f);
        float fgL = 0.2126f * fgR + 0.7152f * fgG + 0.0722f * fgB;

        return Math.abs((fgL + 0.05f) / (bgL + 0.05f));
    }

    /**
     * @return the clamped {@param value} between the provided {@param min} and {@param max}.
     */
    public static float clamp(float value, float min, float max) {
        return Math.max(min, Math.min(max, value));
    }
}