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Add flood fill (#224)
* add FloodFill.cs * add FloodFillTest.cs * update DIRECTORY.md * update README.md
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‎Algorithms.Tests/Other/FloodFillTest.cs

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using System;
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using NUnit.Framework;
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using FluentAssertions;
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using System.Drawing;
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namespace FloodFillTest
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{
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public static class Tests
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{
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private static Color black = Color.FromArgb(255, 0, 0, 0);
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private static Color green = Color.FromArgb(255, 0, 255, 0);
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private static Color violet = Color.FromArgb(255, 255, 0, 255);
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private static Color white = Color.FromArgb(255, 255, 255, 255);
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private static Color orange = Color.FromArgb(255, 255, 128, 0);
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[Test]
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public static void BreadthFirstSearch_ThrowsArgumentOutOfRangeException()
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{
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Action act = () => Algorithms.Other.FloodFill.BreadthFirstSearch(GenerateTestBitmap(), (10, 10), black, white);
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act.Should().Throw<ArgumentOutOfRangeException>();
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}
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[Test]
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public static void DepthFirstSearch_ThrowsArgumentOutOfRangeException()
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{
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Action act = () => Algorithms.Other.FloodFill.DepthFirstSearch(GenerateTestBitmap(), (-1, -1), black, white);
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act.Should().Throw<ArgumentOutOfRangeException>();
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}
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[Test]
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public static void BreadthFirstSearch_Test1()
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{
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TestAlgorithm(Algorithms.Other.FloodFill.BreadthFirstSearch, (1, 1), green, orange, (1, 1), orange);
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}
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[Test]
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public static void BreadthFirstSearch_Test2()
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{
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TestAlgorithm(Algorithms.Other.FloodFill.BreadthFirstSearch, (1, 1), green, orange, (0, 1), violet);
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}
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[Test]
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public static void BreadthFirstSearch_Test3()
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{
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TestAlgorithm(Algorithms.Other.FloodFill.BreadthFirstSearch, (1, 1), green, orange, (0, 1), violet);
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}
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[Test]
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public static void BreadthFirstSearch_Test4()
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{
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TestAlgorithm(Algorithms.Other.FloodFill.BreadthFirstSearch, (1, 1), green, orange, (6, 4), white);
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}
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[Test]
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public static void DepthFirstSearch_Test1()
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{
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TestAlgorithm(Algorithms.Other.FloodFill.DepthFirstSearch, (1, 1), green, orange, (1, 1), orange);
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}
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[Test]
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public static void DepthFirstSearch_Test2()
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{
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TestAlgorithm(Algorithms.Other.FloodFill.DepthFirstSearch, (1, 1), green, orange, (0, 1), violet);
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}
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[Test]
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public static void DepthFirstSearch_Test3()
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{
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TestAlgorithm(Algorithms.Other.FloodFill.DepthFirstSearch, (1, 1), green, orange, (0, 1), violet);
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}
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[Test]
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public static void DepthFirstSearch_Test4()
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{
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TestAlgorithm(Algorithms.Other.FloodFill.DepthFirstSearch, (1, 1), green, orange, (6, 4), white);
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}
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private static Bitmap GenerateTestBitmap()
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{
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Color[,] layout =
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{
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{violet, violet, green, green, black, green, green},
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{violet, green, green, black, green, green, green},
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{green, green, green, black, green, green, green},
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{black, black, green, black, white, white, green},
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{violet, violet, black, violet, violet, white, white},
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{green, green, green, violet, violet, violet, violet},
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{violet, violet, violet, violet, violet, violet, violet}
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};
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Bitmap bitmap = new Bitmap(7, 7);
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for (int x = 0; x < layout.GetLength(0); x++)
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{
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for (int y = 0; y < layout.GetLength(1); y++)
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{
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bitmap.SetPixel(x, y, layout[y, x]);
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}
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}
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return bitmap;
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}
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private static void TestAlgorithm(
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Action<Bitmap, ValueTuple<int, int>, Color, Color> algorithm,
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ValueTuple<int, int> fillLocation,
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Color targetColor,
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Color replacementColor,
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ValueTuple<int, int> testLocation,
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Color expectedColor)
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{
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Bitmap bitmap = GenerateTestBitmap();
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algorithm(bitmap, fillLocation, targetColor, replacementColor);
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Color actualColor = bitmap.GetPixel(testLocation.Item1, testLocation.Item2);
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actualColor.Should().Be(expectedColor);
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}
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}
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}

‎Algorithms/Other/FloodFill.cs

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using System;
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using System.Collections.Generic;
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using System.Drawing;
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using System.Numerics;
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namespace Algorithms.Other
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{
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/// <summary>
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/// Flood fill, also called seed fill, is an algorithm that determines and
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/// alters the area connected to a given node in a multi-dimensional array with
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/// some matching attribute. It is used in the "bucket" fill tool of paint
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/// programs to fill connected, similarly-colored areas with a different color.
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/// (description adapted from https://en.wikipedia.org/wiki/Flood_fill)
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/// (see also: https://www.techiedelight.com/flood-fill-algorithm/).
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/// </summary>
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public static class FloodFill
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{
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private static List<(int xOffset, int yOffset)> neighbors = new List<(int xOffset, int yOffset)> { (-1, -1), (-1, 0), (-1, 1), (0, -1), (0, 1), (1, -1), (1, 0), (1, 1) };
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/// <summary>
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/// Implements the flood fill algorithm through a breadth-first approach using a queue.
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/// </summary>
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/// <param name="bitmap">The bitmap to which the algorithm is applied.</param>
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/// <param name="location">The start location on the bitmap.</param>
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/// <param name="targetColor">The old color to be replaced.</param>
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/// <param name="replacementColor">The new color to replace the old one.</param>
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public static void BreadthFirstSearch(Bitmap bitmap, (int x, int y) location, Color targetColor, Color replacementColor)
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{
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if (location.x < 0 || location.x >= bitmap.Width || location.y < 0 || location.y >= bitmap.Height)
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{
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throw new ArgumentOutOfRangeException(nameof(location), $"{nameof(location)} should point to a pixel within the bitmap");
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}
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var queue = new List<(int x, int y)>();
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queue.Add(location);
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while (queue.Count > 0)
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{
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BreadthFirstFill(bitmap, location, targetColor, replacementColor, queue);
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}
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}
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/// <summary>
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/// Implements the flood fill algorithm through a depth-first approach through recursion.
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/// </summary>
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/// <param name="bitmap">The bitmap to which the algorithm is applied.</param>
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/// <param name="location">The start location on the bitmap.</param>
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/// <param name="targetColor">The old color to be replaced.</param>
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/// <param name="replacementColor">The new color to replace the old one.</param>
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public static void DepthFirstSearch(Bitmap bitmap, (int x, int y) location, Color targetColor, Color replacementColor)
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{
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if (location.x < 0 || location.x >= bitmap.Width || location.y < 0 || location.y >= bitmap.Height)
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{
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throw new ArgumentOutOfRangeException(nameof(location), $"{nameof(location)} should point to a pixel within the bitmap");
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}
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DepthFirstFill(bitmap, location, targetColor, replacementColor);
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}
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private static void BreadthFirstFill(Bitmap bitmap, (int x, int y) location, Color targetColor, Color replacementColor, List<(int x, int y)> queue)
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{
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(int x, int y) currentLocation = queue[0];
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queue.RemoveAt(0);
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if (bitmap.GetPixel(currentLocation.x, currentLocation.y) == targetColor)
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{
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bitmap.SetPixel(currentLocation.x, currentLocation.y, replacementColor);
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for (int i = 0; i < neighbors.Count; i++)
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{
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int x = currentLocation.x + neighbors[i].xOffset;
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int y = currentLocation.y + neighbors[i].yOffset;
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if (x >= 0 && x < bitmap.Width && y >= 0 && y < bitmap.Height)
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{
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queue.Add((x, y));
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}
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}
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}
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}
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private static void DepthFirstFill(Bitmap bitmap, (int x, int y) location, Color targetColor, Color replacementColor)
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{
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if (bitmap.GetPixel(location.x, location.y) == targetColor)
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{
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bitmap.SetPixel(location.x, location.y, replacementColor);
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for (int i = 0; i < neighbors.Count; i++)
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{
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int x = location.x + neighbors[i].xOffset;
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int y = location.y + neighbors[i].yOffset;
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if (x >= 0 && x < bitmap.Width && y >= 0 && y < bitmap.Height)
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{
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DepthFirstFill(bitmap, (x, y), targetColor, replacementColor);
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}
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}
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}
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}
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}
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}

‎DIRECTORY.md

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* [Mandelbrot](https://github.com/TheAlgorithms/C-Sharp/blob/master/Algorithms/Other/Mandelbrot.cs)
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* [Koch Snowflake](https://github.com/TheAlgorithms/C-Sharp/blob/master/Algorithms/Other/KochSnowflake.cs)
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* [RGB-HSV Conversion](https://github.com/TheAlgorithms/C-Sharp/blob/master/Algorithms/Other/RGBHSVConversion.cs)
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* [Flood Fill](https://github.com/TheAlgorithms/C-Sharp/blob/master/Algorithms/Other/FloodFill.cs)
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## Problems
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* [Stable Marriage](https://github.com/TheAlgorithms/C-Sharp/blob/master/Algorithms/Problems/StableMarriage/GaleShapley.cs)
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* [N-Queens](https://github.com/TheAlgorithms/C-Sharp/blob/master/Algorithms/Problems/NQueens/BacktrackingNQueensSolver.cs)

‎README.md

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* [Mandelbrot](./Algorithms/Other/Mandelbrot.cs)
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* [Koch Snowflake](./Algorithms/Other/KochSnowflake.cs)
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* [RGB-HSV Conversion](./Algorithms/Other/RGBHSVConversion.cs)
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* [Flood Fill](./Algorithms/Other/FloodFill.cs)
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* [Problems](./Algorithms/Problems)
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* [Stable Marriage](./Algorithms/Problems/StableMarriage)
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* [Gale-Shapley](./Algorithms/Problems/StableMarriage/GaleShapley.cs)

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