content: /*
   * Copyright 2021 Google LLC
   *
   * 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.google.material.color.quantize;
  
  import com.google.material.color.utils.ColorUtils;
  
  /**
   * Provides conversions needed for K-Means quantization. Converting input to points, and converting
   * the final state of the K-Means algorithm to colors.
   */
  public final class PointProviderLab implements PointProvider {
      /**
       * Convert a color represented in ARGB to a 3-element array of L*a*b* coordinates of the color.
       */
      @Override
      public double[] fromInt(int argb) {
          double[] lab = ColorUtils.labFromArgb(argb);
          return new double[]{lab[0], lab[1], lab[2]};
      }
  
      /**
       * Convert a 3-element array to a color represented in ARGB.
       */
      @Override
      public int toInt(double[] lab) {
          return ColorUtils.argbFromLab(lab[0], lab[1], lab[2]);
      }
  
      /**
       * Standard CIE 1976 delta E formula also takes the square root, unneeded here. This method is
       * used by quantization algorithms to compare distance, and the relative ordering is the same,
       * with or without a square root.
       *
       * <p>This relatively minor optimization is helpful because this method is called at least once
       * for each pixel in an image.
       */
      @Override
      public double distance(double[] one, double[] two) {
          double dL = (one[0] - two[0]);
          double dA = (one[1] - two[1]);
          double dB = (one[2] - two[2]);
          return (dL * dL + dA * dA + dB * dB);
    }
  }
  