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    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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 org.apache.commons.imaging.palette;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  
  import java.awt.image.BufferedImage;
  
  import org.apache.commons.imaging.AbstractImagingTest;
  import org.apache.commons.imaging.ImagingException;
  import org.junit.jupiter.api.Test;
  
  public class PaletteQuantizationTest extends AbstractImagingTest {
  
      private void checkPaletteDetails(final BufferedImage image, final int limit, final int expectedSize) throws ImagingException {
          final PaletteFactory paletteFactory = new PaletteFactory();
          Palette palette;
  
          palette = paletteFactory.makeExactRgbPaletteSimple(image, limit);
          // too small palettes are null
          boolean exact = false;
          if (palette != null) {
              assertEquals(expectedSize, palette.length());
              // checkUniqueColors(image, palette);
              exact = true;
          }
          if (exact) {
              // checkDithering(image, palette);
          }
  
          palette = paletteFactory.makeQuantizedRgbaPalette(image, false, limit);
          assertEquals(expectedSize, palette.length());
          checkUniqueColors(image, palette);
          if (exact) {
              checkPixelsAreIdentical(image, palette);
          }
  
          palette = paletteFactory.makeQuantizedRgbPalette(image, limit);
          assertEquals(expectedSize, palette.length());
          // checkUniqueColors(image, palette);
          if (exact) {
              // checkDithering(image, palette);
          }
  
          final MedianCutQuantizer medianCutQuantizer = new MedianCutQuantizer(true);
          palette = medianCutQuantizer.process(image, limit, new MostPopulatedBoxesMedianCut());
          assertEquals(expectedSize, palette.length());
          checkUniqueColors(image, palette);
          if (exact) {
              checkPixelsAreIdentical(image, palette);
          }
      }
  
      private void checkPixelsAreIdentical(final BufferedImage src, final Palette palette) throws ImagingException {
          final BufferedImage dst = new BufferedImage(src.getWidth(), src.getHeight(), BufferedImage.TYPE_INT_RGB);
          dst.getGraphics().drawImage(src, 0, 0, src.getWidth(), src.getHeight(), null);
          Dithering.applyFloydSteinbergDithering(dst, palette);
          for (int y = 0; y < src.getHeight(); y++) {
              for (int x = 0; x < src.getWidth(); x++) {
                  assertEquals(src.getRGB(x, y), dst.getRGB(x, y));
              }
          }
      }
  
      private void checkUniqueColors(final BufferedImage src, final Palette palette) throws ImagingException {
          final BufferedImage dst = new BufferedImage(src.getWidth(), src.getHeight(), BufferedImage.TYPE_INT_RGB);
          dst.getGraphics().drawImage(src, 0, 0, src.getWidth(), src.getHeight(), null);
          Dithering.applyFloydSteinbergDithering(dst, palette);
          final Palette ditheredPalette = new PaletteFactory().makeExactRgbPaletteSimple(dst, palette.length() * 2);
          assertEquals(palette.length(), ditheredPalette.length());
      }
  
      @Test
      public void testPaletteQuantization() throws ImagingException {
          final BufferedImage whiteImage = new BufferedImage(10, 10, BufferedImage.TYPE_INT_RGB);
          for (int y = 0; y < whiteImage.getHeight(); y++) {
              for (int x = 0; x < whiteImage.getWidth(); x++) {
                  whiteImage.setRGB(x, y, 0xFFFFFF);
              }
          }
          checkPaletteDetails(whiteImage, 10, 1);
  
          final BufferedImage whiteAndBlackImage = new BufferedImage(10, 10, BufferedImage.TYPE_INT_RGB);
          for (int y = 0; y < whiteImage.getHeight(); y++) {
              for (int x = 0; x < 5; x++) {
                 whiteAndBlackImage.setRGB(x, y, 0xFFFFFF);
             }
             for (int x = 5; x < 10; x++) {
                 whiteAndBlackImage.setRGB(x, y, 0x000000);
             }
         }
         checkPaletteDetails(whiteAndBlackImage, 10, 2);
 
         final BufferedImage rainbowImage = new BufferedImage(9, 10, BufferedImage.TYPE_INT_RGB);
         for (int y = 0; y < whiteImage.getHeight(); y++) {
             for (int x = 0; x < 3; x++) {
                 rainbowImage.setRGB(x, y, 0xFF0000);
             }
             for (int x = 3; x < 6; x++) {
                 rainbowImage.setRGB(x, y, 0x00FF00);
             }
             for (int x = 6; x < 9; x++) {
                 rainbowImage.setRGB(x, y, 0x0000FF);
             }
         }
         checkPaletteDetails(rainbowImage, 10, 3);
         checkPaletteDetails(rainbowImage, 2, 2);
     }
 }