This method calculates the suitable contrasting color that is viewable. - Android User Interface

Android examples for User Interface:TableRow

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Description

This method calculates the suitable contrasting color that is viewable.

Demo Code

/*/*from   ww  w . j av  a2  s. c  o m*/
 * Copyright (C) 2015 Twitter, Inc.
 *
 * 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.java2s;
import android.graphics.Color;

public class Main {
    private static final int RGB_TOTAL_COLORS = 256;
    private static final float DEFAULT_LIGHTNESS_THRESHOLD = .6f;
    private static final int OPAQUE_ALPHA = Math.round(255 * 1.0f);
    private static final int TRANSPARENT_ALPHA = Math.round(255 * 0.9f);
    private static final int COLOR_FULLY_WHITE = Math.round(255 * 1.0f);
    private static final int COLOR_PARTIALLY_BLACK = Math.round(255 * 0.4f);

    /**
     * This method calculates the suitable contrasting color that is viewable.
     *
     * @param color A color value.
     * @return  The calculated contrasting color that is viewable.
     */
    public static int calculateContrastingColor(final int color) {
        final boolean isLightColor = isLightColor(color);
        final int alpha = isLightColor ? OPAQUE_ALPHA : TRANSPARENT_ALPHA;
        final int rgbColor = isLightColor ? COLOR_PARTIALLY_BLACK
                : COLOR_FULLY_WHITE;
        return Color.argb(alpha, rgbColor, rgbColor, rgbColor);
    }

    public static boolean isLightColor(final int color) {
        return isLightColor(color, DEFAULT_LIGHTNESS_THRESHOLD);
    }

    /**
     * This method uses HSL to determine in a human eyesight terms if a color is light or not.
     * See: http://en.wikipedia.org/wiki/HSL_and_HSV. The threshold values are from ITU Rec. 709
     * http://en.wikipedia.org/wiki/Rec._709#Luma_coefficients
     *
     *
     * @param  color A color value
     * @param  factor A factor of lightness measured between 0-1.0
     * @return Whether or not the color is considered light
     */
    public static boolean isLightColor(final int color, final float factor) {
        final int r = Color.red(color);
        final int g = Color.green(color);
        final int b = Color.blue(color);

        final double threshold = 0.21 * r + 0.72 * g + 0.07 * b;
        return threshold > (RGB_TOTAL_COLORS * factor);
    }
}

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