/// <summary>
/// Retrieves a sequence of adjacent horizontal same-color segments
/// </summary>
/// <param name="field">from this field</param>
/// <param name="y"></param>
/// <returns></returns>
static SpanList GetSpansFromLine(Field field, int y)
{
SpanList result = new SpanList();
Color currentElement = field[0, y];
Span current = new Span()
{
StartX = 0, Y = y, Color = currentElement
};
for (int x = 1; x < field.Size.Width; x++)
{
if (field[x, y] != currentElement)
{
currentElement = field[x, y];
current.EndX = x - 1;
result.Add(current);
current = new Span()
{
StartX = x, Y = y, Color = currentElement
};
}
}
current.EndX = field.Size.Width - 1;
result.Add(current);
return(result);
}
public void ShiftGenerations(ConnectedComponentSet complete)
{
// add first generation to the second
Spans.UnionWith(FrontalSpans);
// if the Generation 0 hasn't been filled,
// it means the component is complete and won't grow anymore
if (NewFrontalSpans.Count == 0)
{
// add it to the list of complete components
complete.Add(this);
}
else
{
// Generation 0 grows older and becomes Generation 1
FrontalSpans = NewFrontalSpans;
// And a new Generation 0 is born
NewFrontalSpans = new SpanList();
}
}
/// <summary>
/// Calculates and returns a set of 4-connected components in a field
/// </summary>
/// <param name="field">The two-dimensional matrix with colors</param>
/// <returns></returns>
public static ConnectedComponentSet FindConnectedComponents(Field field)
{
ConnectedComponentSet result = new ConnectedComponentSet();
ConnectedComponentSet current = new ConnectedComponentSet();
// we scan the entire matrix line by line
for (int y = 0; y < field.Size.Height; y++)
{
SpanList spansOnCurrentLine = GetSpansFromLine(field, y);
foreach (var span in spansOnCurrentLine)
{
PlaceSpan(span, current);
}
// check which components didn't change since the previous iteration
ConnectedComponentSet complete = new ConnectedComponentSet();
foreach (var component in current)
{
component.ShiftGenerations(complete);
}
foreach (var component in complete)
{
component.FrontalSpans.Clear();
current.Remove(component);
result.Add(component);
}
}
// We reached the bottom
// For all the remaining components, add them to the result
foreach (var component in current)
{
component.Spans.UnionWith(component.FrontalSpans);
component.Spans.UnionWith(component.NewFrontalSpans);
result.Add(component);
}
return(result);
}
public ConnectedComponent()
{
Spans = new SpanList();
FrontalSpans = new SpanList();
NewFrontalSpans = new SpanList();
}
public void UnionWith(SpanList otherSpans)
{
this.AddRange(otherSpans);
}
