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);
}
/// <summary>
/// Classifies a span with regard to already processed spans
/// </summary>
/// <param name="currentSpan"></param>
/// <param name="currentComponentSet"></param>
static void PlaceSpan(Span currentSpan, ConnectedComponentSet currentComponentSet)
{
if (currentSpan.Y == 0)
{
// for the first row, just accumulate the spans in the Generation 0
currentComponentSet.AddNewComponentFromSpan(currentSpan);
return;
}
// find all spans from Generation 1 that "touch" this span
ConnectedComponentSet componentsToJoin = new ConnectedComponentSet();
componentsToJoin.AddRange(
currentComponentSet.Where(
component => component.FrontalSpans.IntersectsWith(currentSpan)));
// if we "touch" 0 existing components, create a new one
if (componentsToJoin.Count == 0)
{
currentComponentSet.AddNewComponentFromSpan(currentSpan);
}
// if we touch one component, append the current span to its bottom
else if (componentsToJoin.Count == 1)
{
componentsToJoin[0].NewFrontalSpans.Add(currentSpan);
}
// if we touch more than one component, it means they all belong together.
// Now we unite all of these components into one.
else
{
for (int i = 1; i < componentsToJoin.Count; i++)
{
componentsToJoin[0].NewFrontalSpans.Add(currentSpan);
componentsToJoin[0].UnionWith(componentsToJoin[i]);
currentComponentSet.Remove(componentsToJoin[i]);
}
}
}
