ColorUtil.java

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

package com.facebook.react.views.view;

import android.graphics.PixelFormat;

/**
 * Simple utility class for manipulating colors, based on Fresco's
 * DrawableUtils (https://github.com/facebook/fresco).
 * For a small helper like this, copying is simpler than adding
 * a dependency on com.facebook.fresco.drawee.
 */
public class ColorUtil {

  /**
   * Multiplies the color with the given alpha.
   * @param color color to be multiplied
   * @param alpha value between 0 and 255
   * @return multiplied color
   */
  public static int multiplyColorAlpha(int color, int alpha) {
    if (alpha == 255) {
      return color;
    }
    if (alpha == 0) {
      return color & 0x00FFFFFF;
    }
    alpha = alpha + (alpha >> 7); // make it 0..256
    int colorAlpha = color >>> 24;
    int multipliedAlpha = colorAlpha * alpha >> 8;
    return (multipliedAlpha << 24) | (color & 0x00FFFFFF);
  }

  /**
   * Gets the opacity from a color. Inspired by Android ColorDrawable.
   * @return opacity expressed by one of PixelFormat constants
   */
  public static int getOpacityFromColor(int color) {
    int colorAlpha = color >>> 24;
    if (colorAlpha == 255) {
      return PixelFormat.OPAQUE;
    } else if (colorAlpha == 0) {
      return PixelFormat.TRANSPARENT;
    } else {
      return PixelFormat.TRANSLUCENT;
    }
  }
}