PixelDistanceProvider

package com.hypixel.hytale.server.worldgen.zoom;

import it.unimi.dsi.fastutil.ints.IntOpenHashSet;
import it.unimi.dsi.fastutil.ints.IntSet;
import javax.annotation.Nonnull;

public class PixelDistanceProvider {
   private static final int TABLE_SIZE = 8;
   @Nonnull
   protected final PixelProvider image;
   protected final int width;
   protected final int height;
   protected final int cellsX;
   protected final int cellsY;
   @Nonnull
   protected final PixelDistanceProvider.IPixelSet[] table;
   @Nonnull
   protected final IntSet pixels;

   public PixelDistanceProvider(@Nonnull PixelProvider image) {
      this.image = image;
      this.width = image.getWidth();
      this.height = image.getHeight();
      this.cellsX = image.getWidth() / 8;
      this.cellsY = image.getHeight() / 8;
      this.table = new PixelDistanceProvider.IPixelSet[this.cellsX * this.cellsY];
      this.pixels = new IntOpenHashSet();
      this.prepareSegmentTable();
   }

   @Nonnull
   public IntSet getColors() {
      return this.pixels;
   }

   public double distanceSqToDifferentPixel(double ox, double oy, int px, int py) {
      px = this.clampX(px);
      py = this.clampY(py);
      int color = this.image.getPixel(px, py);
      int cellX = px / 8;
      int cellY = py / 8;
      double distance = 1.0 / 0.0;
      int minX = Math.max(cellX - 1, 0);
      int maxX = Math.min(cellX + 2, this.cellsX);
      int minY = Math.max(cellY - 1, 0);
      int maxY = Math.min(cellY + 2, this.cellsY);

      for (int ix = minX; ix < maxX; ix++) {
         for (int iy = minY; iy < maxY; iy++) {
            double dist = this.distanceSqToDiffInSeq(ox, oy, color, ix, iy);
            if (dist < distance) {
               distance = dist;
            }
         }
      }

      return distance;
   }

   protected double distanceSqToDiffInSeq(double ox, double oy, int pixel, int cellX, int cellY) {
      double distSq = 1.0 / 0.0;
      if (this.hasDifferentPixel(cellX, cellY, pixel)) {
         int offsetX = cellX * 8;
         int offsetY = cellY * 8;

         for (int ix = 0; ix < 8; ix++) {
            int px = ix + offsetX;

            for (int iy = 0; iy < 8; iy++) {
               int py = iy + offsetY;
               if (pixel != this.image.getPixel(px, py)) {
                  double dist = distanceSqToPixel(ox, oy, px, py);
                  if (dist < distSq) {
                     distSq = dist;
                  }
               }
            }
         }
      }

      return distSq;
   }

   protected boolean hasDifferentPixel(int cellX, int cellY, int pixel) {
      PixelDistanceProvider.IPixelSet pixelSet = this.table[this.cellIndex(cellX, cellY)];
      return !pixelSet.contains(pixel) || pixelSet.size() > 1;
   }

   private void prepareSegmentTable() {
      for (int cellX = 0; cellX < this.cellsX; cellX++) {
         for (int cellY = 0; cellY < this.cellsY; cellY++) {
            IntSet colors = new IntOpenHashSet();
            int offsetX = cellX * 8;
            int offsetY = cellY * 8;

            for (int ix = 0; ix < 8; ix++) {
               for (int iy = 0; iy < 8; iy++) {
                  int x = ix + offsetX;
                  int y = iy + offsetY;
                  if (x < this.width && y < this.height) {
                     colors.add(this.image.getPixel(x, y));
                  }
               }
            }

            this.pixels.addAll(colors);
            if (colors.size() == 1) {
               this.table[this.cellIndex(cellX, cellY)] = new PixelDistanceProvider.SinglePixelSet(colors.iterator().nextInt());
            } else {
               this.table[this.cellIndex(cellX, cellY)] = new PixelDistanceProvider.MultiplePixelSet(colors);
            }
         }
      }
   }

   protected int clampX(int x) {
      if (x < 0) {
         return 0;
      } else {
         return x >= this.width ? this.width - 1 : x;
      }
   }

   protected int clampY(int y) {
      if (y < 0) {
         return 0;
      } else {
         return y >= this.height ? this.height - 1 : y;
      }
   }

   protected int cellIndex(int cellX, int cellY) {
      return cellX * this.cellsY + cellY;
   }

   private static double distanceSqToPixel(double ox, double oy, int px, int py) {
      double dx = Math.max(Math.max((double)px - ox, ox - (double)px - 1.0), 0.0);
      double dy = Math.max(Math.max((double)py - oy, oy - (double)py - 1.0), 0.0);
      return dx * dx + dy * dy;
   }

   private interface IPixelSet {
      boolean contains(int var1);

      int size();
   }

   private static class MultiplePixelSet implements PixelDistanceProvider.IPixelSet {
      private final IntSet pixels;

      MultiplePixelSet(IntSet pixels) {
         this.pixels = pixels;
      }

      @Override
      public boolean contains(int pixel) {
         return this.pixels.contains(pixel);
      }

      @Override
      public int size() {
         return this.pixels.size();
      }

      @Nonnull
      @Override
      public String toString() {
         return "MultiplePixelSet{pixels=" + this.pixels + "}";
      }
   }

   private static class SinglePixelSet implements PixelDistanceProvider.IPixelSet {
      private final int pixel;

      SinglePixelSet(int pixel) {
         this.pixel = pixel;
      }

      @Override
      public boolean contains(int pixel) {
         return this.pixel == pixel;
      }

      @Override
      public int size() {
         return 1;
      }

      @Nonnull
      @Override
      public String toString() {
         return "SinglePixelSet{pixel=" + this.pixel + "}";
      }
   }
}