Image IGraphicalMazeSolver.GenerateSolution(GraphicalMaze maze)
{
if (maze == null)
{
throw new ArgumentNullException(nameof(maze));
}
// Find start pixel
var startPixel = FindStartPixel(maze);
if (startPixel == null)
{
return(maze.MazeImage); // No start pixel found
}
var solutionImage = new Bitmap(maze.MazeImage);
// Move up from start pixel until wall reached
var currPixel = startPixel;
var nextPixel = maze.GetPixelTop(currPixel);
while (!nextPixel.IsColor(maze.WallColor))
{
currPixel = nextPixel;
nextPixel = maze.GetPixelTop(currPixel);
if (nextPixel.IsColor(maze.FinishColor))
{
return(solutionImage);
}
solutionImage.SetPixel(currPixel.X, currPixel.Y, maze.SolutionColor);
}
var startWallPixel = currPixel;
var travelDirection = Direction.Right;
var wallDirection = Direction.Up;
while (!currPixel.IsColor(maze.FinishColor))
{
var nextStep = FollowWall(maze, currPixel, travelDirection, wallDirection);
solutionImage.SetPixel(currPixel.X, currPixel.Y, maze.SolutionColor);
currPixel = nextStep.Item1;
travelDirection = nextStep.Item2;
wallDirection = nextStep.Item3;
if (currPixel.Equals(startWallPixel))
{
return(null); // No solution found if looped around to the first wall pixel
}
}
solutionImage.SetPixel(startPixel.X, startPixel.Y, maze.StartColor); // Reapply start pixel color
return(solutionImage);
}
public void Execute(string[] args)
{
// Validate arguments
if (args.Length != 2)
{
Console.Error.WriteLine("Incorrect number of arguments found.");
Exit(-1);
}
// Process arguments
var currentDirectory = Directory.GetCurrentDirectory();
var sourceFile = Path.Combine(currentDirectory, args[0]);
var outputFile = Path.Combine(currentDirectory, args[1]);
// TODO: Validate file formats
// Get source image
try
{
var sourceImage = Image.FromFile(sourceFile);
var graphicalMaze = GraphicalMaze.Create(sourceImage, DefaultWallColor, DefaultStartColor,
DefaultFinishColor,
DefaultSolutionColor);
// Generate cleaned image
var cleanedImage = CleanMaze(graphicalMaze);
// Write solution image, creating the directory if necessary
var ouputDirectory = Path.GetDirectoryName(outputFile);
if (ouputDirectory != null)
{
Directory.CreateDirectory(ouputDirectory);
cleanedImage.Save(outputFile);
}
else
{
Console.Error.WriteLine("Cannot retrieve directoy information for output file path ("
+ outputFile + ".");
Exit(-1);
}
}
catch (FileNotFoundException)
{
Console.Error.WriteLine("Source image not found (" + sourceFile + ").");
Exit(-1);
}
// Solution generated successfully
if (System.Diagnostics.Debugger.IsAttached)
{
Console.WriteLine("Image cleaned and saved (" + outputFile + ".");
}
Exit(0);
}
private static GraphicalMazePixel FindStartPixel(GraphicalMaze maze)
{
var startingY = 0;
var endingY = maze.Height;
var startingX = 0;
var endingX = maze.Width;
// Spiral iterate, since the start point is most likely on the outside of the maze
while (startingY < endingY && startingX < endingX)
{
// Iterate over the first row from the remaining rows
for (var x = startingX; x < endingX; x++)
{
if (maze.GetPixel(x, startingY).IsColor(maze.StartColor))
{
return(maze.GetPixel(x, startingY));
}
}
startingY++;
// Iterate over the last column from the remaining columns
for (var y = startingY; y < endingY; y++)
{
if (maze.GetPixel(endingX - 1, y).IsColor(maze.StartColor))
{
return(maze.GetPixel(endingX - 1, y));
}
}
endingX--;
// Iterate over the last row from the remaining rows
for (var x = startingX; x < endingX; x++)
{
if (maze.GetPixel(x, endingY - 1).IsColor(maze.StartColor))
{
return(maze.GetPixel(x, endingY - 1));
}
}
endingY--;
// Iterate over the first column from the remaining columns
for (var y = startingY; y < endingY; y++)
{
if (maze.GetPixel(startingX, y).IsColor(maze.StartColor))
{
return(maze.GetPixel(startingX, y));
}
}
startingX++;
}
return(null);
}
public static Image CleanMaze(GraphicalMaze maze)
{
// TODO Consider use of ColorMask for more efficient operation
var palette = new[] { maze.WallColor, maze.StartColor, maze.FinishColor, Color.White };
var cleanedImage = new Bitmap(maze.MazeImage);
for (var y = 0; y < maze.Height; y++)
{
for (var x = 0; x < maze.Width; x++)
{
cleanedImage.SetPixel(x, y, GetNearestColor(palette, maze.MazeImage.GetPixel(x, y)));
}
}
return(cleanedImage);
}
private static List <Point> BestFirstSearch(GraphicalMaze maze, Point startPoint, Point endPoint)
{
var visited = new HashSet <Point>();
// Set of pending nodes to be evaluated, sorted by estimated cost from start to end through the point
var discovered = new Queue <Point>();
discovered.Enqueue(startPoint);
var costMap = new Dictionary <Point, int> {
{ startPoint, 0 }
};
var accessMap = new Dictionary <Point, Point>();
while (discovered.Count > 0)
{
var currentPoint = discovered.Dequeue();
if (currentPoint.Equals(endPoint))
{
return(ReconstructPath(accessMap, currentPoint));
}
visited.Add(currentPoint);
var cost = costMap[Point.Create(currentPoint.X, currentPoint.Y)] + 1;
foreach (var neighbor in maze.GetNeighbors(currentPoint))
{
if (neighbor.IsColor(maze.WallColor) || visited.Contains(neighbor))
{
continue;
}
if (costMap.ContainsKey(neighbor) && cost >= costMap[neighbor])
{
continue; // Not a better path
}
// Record better path
accessMap[neighbor] = currentPoint;
costMap[neighbor] = cost;
discovered.Enqueue(neighbor);
}
}
// No solution found
return(null);
}
public Image GenerateSolution(GraphicalMaze maze)
{
// Find start and end pixels
Point startPoint = null;
Point endPoint = null;
for (var y = 0; y < maze.Height; y++)
{
for (var x = 0; x < maze.Width; x++)
{
var pixel = maze.GetPixel(x, y);
if (pixel.IsColor(maze.StartColor))
{
startPoint = pixel;
}
else if (pixel.IsColor(maze.FinishColor))
{
endPoint = pixel;
}
}
}
if (startPoint == null || endPoint == null)
{
return(null); // No start or end points found
}
// Run best first search
var path = BestFirstSearch(maze, startPoint, endPoint);
if (path == null)
{
return(null); // No solution found
}
var solutionImage = new Bitmap(maze.MazeImage);
foreach (var point in path)
{
solutionImage.SetPixel(point.X, point.Y, maze.SolutionColor);
}
solutionImage.SetPixel(startPoint.X, startPoint.Y, maze.StartColor); // Reapply start pixel color
return(solutionImage);
}
private static Tuple <GraphicalMazePixel, Direction, Direction> FollowWall(GraphicalMaze maze,
Point currentPoint, Direction travelDirection, Direction wallDirection)
{
// Left-hand rule conditions only
while (maze.GetPixel(currentPoint, travelDirection).IsColor(maze.WallColor))
{
// Turn at interior corners
switch (wallDirection)
{
case Direction.Up:
travelDirection = Direction.Down;
wallDirection = Direction.Right;
break;
case Direction.Right:
travelDirection = Direction.Left;
wallDirection = Direction.Down;
break;
case Direction.Down:
travelDirection = Direction.Up;
wallDirection = Direction.Left;
break;
case Direction.Left:
travelDirection = Direction.Right;
wallDirection = Direction.Up;
break;
default:
throw new ArgumentOutOfRangeException(nameof(wallDirection), wallDirection, null);
}
}
var nextPixel = maze.GetPixel(currentPoint, travelDirection);
// Wrap-around if moving away from a wall
switch (travelDirection)
{
case Direction.Up:
if (!maze.GetPixel(nextPixel, Direction.Left).IsColor(maze.WallColor))
{
travelDirection = Direction.Left;
wallDirection = Direction.Down;
}
break;
case Direction.Right:
if (!maze.GetPixel(nextPixel, Direction.Up).IsColor(maze.WallColor))
{
travelDirection = Direction.Up;
wallDirection = Direction.Left;
}
break;
case Direction.Down:
if (!maze.GetPixel(nextPixel, Direction.Right).IsColor(maze.WallColor))
{
travelDirection = Direction.Right;
wallDirection = Direction.Up;
}
break;
case Direction.Left:
if (!maze.GetPixel(nextPixel, Direction.Down).IsColor(maze.WallColor))
{
travelDirection = Direction.Down;
wallDirection = Direction.Right;
}
break;
default:
throw new ArgumentOutOfRangeException(nameof(travelDirection), travelDirection, null);
}
return(new Tuple <GraphicalMazePixel, Direction, Direction>(nextPixel, travelDirection, wallDirection));
}