A simple Flood Fill implementation for Unity3D C# for video games. https://elfgames.com/2016/12/14/identify-unwanted-maze-solutions-using-flood-fill-with-unity3d/

FloodFill.cs

// Copyright (c) 2022 Piero Dotti, Elf Games
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without
// restriction, including without limitation the rights to use,
// copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following
// conditions:

// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.

using UnityEngine;
using System.Collections.Generic;

// Flood Fill implementation for Unity3D C#
// Used in: https://www.elfgamesworks.com/2016/12/14/identify-unwanted-maze-solutions-using-flood-fill-with-unity3d/
public static class ImageUtils
{

	public struct Point {

		public int x;
		public int y;

		public Point(int x, int y) {
			this.x = x;
			this.y = y;
		}
	}

	public static void FloodFill(Texture2D readTexture, Texture2D writeTexture, Color sourceColor, float tollerance, int x, int y) {
		var targetColor = Color.red;
		var q = new Queue<Point> (readTexture.width * readTexture.height);
		q.Enqueue (new Point (x, y));
		int iterations = 0;

		var width = readTexture.width;
		var height = readTexture.height;
		while (q.Count > 0) {
			var point = q.Dequeue ();
			var x1 = point.x;
			var y1 = point.y;
			if (q.Count > width * height) {
				throw new System.Exception ("The algorithm is probably looping. Queue size: " + q.Count);
			}

			if (writeTexture.GetPixel (x1, y1) == targetColor) {
				continue;
			}

			writeTexture.SetPixel (x1, y1, targetColor);


			var newPoint = new Point (x1 + 1, y1);
			if (CheckValidity (readTexture, readTexture.width, readTexture.height, newPoint, sourceColor, tollerance))
				q.Enqueue (newPoint);

			newPoint = new Point (x1 - 1, y1);
			if (CheckValidity (readTexture, readTexture.width, readTexture.height, newPoint, sourceColor, tollerance))
				q.Enqueue (newPoint);

			newPoint = new Point (x1, y1 + 1);
			if (CheckValidity (readTexture, readTexture.width, readTexture.height, newPoint, sourceColor, tollerance))
				q.Enqueue (newPoint);

			newPoint = new Point (x1, y1 - 1);
			if (CheckValidity (readTexture, readTexture.width, readTexture.height, newPoint, sourceColor, tollerance))
				q.Enqueue (newPoint);

			iterations++;
		}
	}

	static bool CheckValidity(Texture2D texture, int width, int height, Point p, Color sourceColor, float tollerance) {
		if (p.x < 0 || p.x >= width) {
			return false;
		}
		if (p.y < 0 || p.y >= height) {
			return false;
		}

		var color = texture.GetPixel(p.x, p.y);

		var distance = Mathf.Abs (color.r - sourceColor.r) +  Mathf.Abs (color.g - sourceColor.g) +  Mathf.Abs (color.b - sourceColor.b);
		return distance <= tollerance;
	}
}

Thank you!
That is exactly what I was looking for!

This looks very useful! It currently doesn't appear to have a license associated with it. I would like to use and build on the code, but only if it has an open-source license. Would you please specify its license? Thanks!

Hi @sprale , I've added a MIT license to it ;)

Thank you!!