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/* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
package org.mozilla.gecko.util;
import android.graphics.Color;
public class ColorUtil {
public static int darken(final int color, final double fraction) {
int red = Color.red(color);
int green = Color.green(color);
int blue = Color.blue(color);
red = darkenColor(red, fraction);
green = darkenColor(green, fraction);
blue = darkenColor(blue, fraction);
final int alpha = Color.alpha(color);
return Color.argb(alpha, red, green, blue);
}
public static int getReadableTextColor(final int backgroundColor) {
final int greyValue = grayscaleFromRGB(backgroundColor);
// 186 chosen rather than the seemingly obvious 128 because of gamma.
if (greyValue < 186) {
return Color.WHITE;
} else {
return Color.BLACK;
}
}
private static int darkenColor(final int color, final double fraction) {
return (int) Math.max(color - (color * fraction), 0);
}
private static int grayscaleFromRGB(final int color) {
final int red = Color.red(color);
final int green = Color.green(color);
final int blue = Color.blue(color);
// Magic weighting taken from a stackoverflow post, supposedly related to how
// humans perceive color.
return (int) (0.299 * red + 0.587 * green + 0.114 * blue);
}
}
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