/// <summary>Returns true if the point is on canvas, otherwise false.</summary>
public bool OnCanvas(Codel codel)
{
return(codel.X >= 0 &&
codel.Y >= 0 &&
codel.X < Width &&
codel.Y < Height);
}
/// <summary>Gets the value of the colour block.</summary>
/// <param name="position">
/// A position of the program that is member of the colour block.
/// </param>
public ColourBlock SelectBlock(Codel position)
{
if (this[position].IsBlack)
{
return(ColourBlock.Border);
}
var val = _blocks[position.X][position.Y];
return(val is null
? DetermineColourBlock(position)
: val);
}
/// <summary>Determines the value of the colour block.</summary>
/// <param name="pointer">
/// A point of the program that is member of the colour block.
/// </param>
private ColourBlock DetermineColourBlock(Codel pointer)
{
var colour = this[pointer];
var counter = 0;
var visited = new HashSet <Codel>();
var todo = new Queue <Codel>();
todo.Enqueue(pointer);
while (todo.TryDequeue(out var p))
{
if (this[p].IsBlack ||
visited.Contains(p) ||
_blocks[p.X][p.Y] != null)
{
continue;
}
// We don't want to do things twice.
if (!visited.Add(p))
{
continue;
}
var testColour = this[p];
if (colour == testColour)
{
counter++;
todo.Enqueue(p.Next(DirectionPointer.top));
todo.Enqueue(p.Next(DirectionPointer.right));
todo.Enqueue(p.Next(DirectionPointer.down));
todo.Enqueue(p.Next(DirectionPointer.left));
}
}
var codels = visited.Where(p => this[p] == colour);
var block = new ColourBlock(colour, codels);
foreach (var codel in codels)
{
_blocks[codel.X][codel.Y] = block;
}
return(block);
}
/// <summary>Gets the codel of the pointer.</summary> public Colour this[Codel position] => OnCanvas(position) ? _codels[position.X][position.Y] : Colour.Black;
