/// <summary>
/// Simplifies a segment of the line string.
/// </summary>
/// <param name="startIndex">The starting index of the segment.</param>
/// <param name="endIndex">The ending index of the segment.</param>
protected void SimplifySegment(Int32 startIndex, Int32 endIndex)
{
if (endIndex <= startIndex + 1) // the segment is a line
{
return;
}
Double maxDistance = 0;
Int32 maxIndex = startIndex;
// find the most distant coordinate from the line between the starting and ending coordinates
for (Int32 coordinateIndex = startIndex + 1; coordinateIndex < endIndex; coordinateIndex++)
{
Double distance = LineAlgorithms.Distance(_source[startIndex], _source[endIndex], _source[coordinateIndex], PrecisionModel);
if (distance > maxDistance)
{
maxIndex = coordinateIndex;
maxDistance = distance;
}
}
if (maxDistance <= _delta) // the distance is smaller than the delta, the all coordinates should be removed
{
return;
}
// recursively simplify both segments
_marks[maxIndex] = true;
SimplifySegment(startIndex, maxIndex);
SimplifySegment(maxIndex, startIndex);
}
/// <summary>
/// Simplifies a segment of the line string.
/// </summary>
/// <param name="startIndex">The starting index of the segment.</param>
/// <param name="endIndex">The ending index of the segment.</param>
private void SimplifySegment(Int32 startIndex, Int32 endIndex)
{
if (this.Source[startIndex] == null || this.Source[endIndex] == null)
{
return;
}
if (endIndex <= startIndex + 1) // the segment is a line
{
return;
}
Double maxDistance = 0;
Int32 maxIndex = startIndex;
// find the most distant coordinate from the line between the starting and ending coordinates
for (Int32 coordinateIndex = startIndex + 1; coordinateIndex < endIndex; coordinateIndex++)
{
if (this.Source[coordinateIndex] == null)
{
continue;
}
Double distance = LineAlgorithms.Distance(this.Source[startIndex], this.Source[endIndex], this.Source[coordinateIndex], this.PrecisionModel);
if (distance > maxDistance)
{
maxIndex = coordinateIndex;
maxDistance = distance;
}
}
if (maxDistance <= this.delta)
{
// the distance is smaller than the delta, all coordinates should be removed
return;
}
// recursively simplify both segments
this.marks[maxIndex] = true;
this.SimplifySegment(startIndex, maxIndex);
this.SimplifySegment(maxIndex, startIndex);
}
public void LineAlgorithmsDistanceTest()
{
// distance of a line and a coordinate
Coordinate lineStart = new Coordinate(0, 1);
Coordinate lineEnd = new Coordinate(100, 1);
Coordinate coordinate = new Coordinate(1, 1);
Assert.AreEqual(0, LineAlgorithms.Distance(lineStart, lineEnd, coordinate));
lineStart = new Coordinate(0, 1);
lineEnd = new Coordinate(100, 1);
coordinate = new Coordinate(1, 7);
Assert.AreEqual(6, LineAlgorithms.Distance(lineStart, lineEnd, coordinate));
lineStart = new Coordinate(5, 7);
lineEnd = new Coordinate(5, 70);
coordinate = new Coordinate(5, 6);
Assert.AreEqual(1, LineAlgorithms.Distance(lineStart, lineEnd, coordinate));
lineStart = new Coordinate(5, 7);
lineEnd = new Coordinate(5, 70);
coordinate = new Coordinate(4, 7);
Assert.AreEqual(1, LineAlgorithms.Distance(lineStart, lineEnd, coordinate));
lineStart = new Coordinate(0, 0);
lineEnd = new Coordinate(2, -3);
coordinate = new Coordinate(2, 1);
Assert.AreEqual(2.22, Math.Round(LineAlgorithms.Distance(lineStart, lineEnd, coordinate), 2));
// distance of two lines
lineStart = new Coordinate(0, 0);
lineEnd = new Coordinate(100, 0);
Coordinate secondLineStart = new Coordinate(0, 0);
Coordinate secondLineEnd = new Coordinate(0, 100);
Assert.AreEqual(0, LineAlgorithms.Distance(lineStart, lineEnd, secondLineStart, secondLineEnd));
lineStart = new Coordinate(0, 0);
lineEnd = new Coordinate(100, 0);
secondLineStart = new Coordinate(0, 1);
secondLineEnd = new Coordinate(100, 1);
Assert.AreEqual(1, LineAlgorithms.Distance(lineStart, lineEnd, secondLineStart, secondLineEnd));
lineStart = new Coordinate(2, 4);
lineEnd = new Coordinate(5, 3);
secondLineStart = new Coordinate(6, 2);
secondLineEnd = new Coordinate(6, 6);
Assert.AreEqual(1, LineAlgorithms.Distance(lineStart, lineEnd, secondLineStart, secondLineEnd));
lineStart = new Coordinate(1, 1);
lineEnd = new Coordinate(1, 4);
secondLineStart = new Coordinate(4, 2);
secondLineEnd = new Coordinate(0, 2);
Assert.AreEqual(0, LineAlgorithms.Distance(lineStart, lineEnd, secondLineStart, secondLineEnd));
// distance of an infinite line and a point
lineStart = new Coordinate(1, 1);
CoordinateVector coordinateVector = new CoordinateVector(0, 1);
coordinate = new Coordinate(2, 1500);
Assert.AreEqual(1, LineAlgorithms.Distance(lineStart, coordinateVector, coordinate));
lineStart = new Coordinate(1, 1);
coordinateVector = new CoordinateVector(0, 1);
coordinate = new Coordinate(1, 1500);
Assert.AreEqual(0, LineAlgorithms.Distance(lineStart, coordinateVector, coordinate));
lineStart = new Coordinate(1, 1);
coordinateVector = new CoordinateVector(0, 1);
coordinate = new Coordinate(0, -100);
Assert.AreEqual(1, LineAlgorithms.Distance(lineStart, coordinateVector, coordinate));
lineStart = new Coordinate(2, 4);
coordinateVector = new CoordinateVector(-3, 1);
coordinate = new Coordinate(14, 0);
Assert.AreEqual(0, LineAlgorithms.Distance(lineStart, coordinateVector, coordinate));
lineStart = new Coordinate(2, 4);
coordinateVector = new CoordinateVector(-3, 1);
coordinate = new Coordinate(5, 3);
Assert.AreEqual(0, LineAlgorithms.Distance(lineStart, coordinateVector, coordinate));
}
public void LineAlgorithmsDistanceTest()
{
// distance of a line and a coordinate
Coordinate lineStart = new Coordinate(0, 1);
Coordinate lineEnd = new Coordinate(100, 1);
Coordinate coordinate = new Coordinate(1, 1);
LineAlgorithms.Distance(lineStart, lineEnd, coordinate).ShouldBe(0);
lineStart = new Coordinate(0, 1);
lineEnd = new Coordinate(100, 1);
coordinate = new Coordinate(1, 7);
LineAlgorithms.Distance(lineStart, lineEnd, coordinate).ShouldBe(6);
lineStart = new Coordinate(5, 7);
lineEnd = new Coordinate(5, 70);
coordinate = new Coordinate(5, 6);
LineAlgorithms.Distance(lineStart, lineEnd, coordinate).ShouldBe(1);
lineStart = new Coordinate(5, 7);
lineEnd = new Coordinate(5, 70);
coordinate = new Coordinate(4, 7);
LineAlgorithms.Distance(lineStart, lineEnd, coordinate).ShouldBe(1);
lineStart = new Coordinate(0, 0);
lineEnd = new Coordinate(2, -3);
coordinate = new Coordinate(2, 1);
LineAlgorithms.Distance(lineStart, lineEnd, coordinate).ShouldBe(2.22, 0.01);
// distance of two lines
lineStart = new Coordinate(0, 0);
lineEnd = new Coordinate(100, 0);
Coordinate secondLineStart = new Coordinate(0, 0);
Coordinate secondLineEnd = new Coordinate(0, 100);
LineAlgorithms.Distance(lineStart, lineEnd, secondLineStart, secondLineEnd).ShouldBe(0);
lineStart = new Coordinate(0, 0);
lineEnd = new Coordinate(100, 0);
secondLineStart = new Coordinate(0, 1);
secondLineEnd = new Coordinate(100, 1);
LineAlgorithms.Distance(lineStart, lineEnd, secondLineStart, secondLineEnd).ShouldBe(1);
lineStart = new Coordinate(2, 4);
lineEnd = new Coordinate(5, 3);
secondLineStart = new Coordinate(6, 2);
secondLineEnd = new Coordinate(6, 6);
LineAlgorithms.Distance(lineStart, lineEnd, secondLineStart, secondLineEnd).ShouldBe(1);
lineStart = new Coordinate(1, 1);
lineEnd = new Coordinate(1, 4);
secondLineStart = new Coordinate(4, 2);
secondLineEnd = new Coordinate(0, 2);
LineAlgorithms.Distance(lineStart, lineEnd, secondLineStart, secondLineEnd).ShouldBe(0);
// distance of an infinite line and a point
lineStart = new Coordinate(1, 1);
CoordinateVector coordinateVector = new CoordinateVector(0, 1);
coordinate = new Coordinate(2, 1500);
LineAlgorithms.Distance(lineStart, coordinateVector, coordinate).ShouldBe(1);
lineStart = new Coordinate(1, 1);
coordinateVector = new CoordinateVector(0, 1);
coordinate = new Coordinate(1, 1500);
LineAlgorithms.Distance(lineStart, coordinateVector, coordinate).ShouldBe(0);
lineStart = new Coordinate(1, 1);
coordinateVector = new CoordinateVector(0, 1);
coordinate = new Coordinate(0, -100);
LineAlgorithms.Distance(lineStart, coordinateVector, coordinate).ShouldBe(1);
lineStart = new Coordinate(2, 4);
coordinateVector = new CoordinateVector(-3, 1);
coordinate = new Coordinate(14, 0);
LineAlgorithms.Distance(lineStart, coordinateVector, coordinate).ShouldBe(0);
lineStart = new Coordinate(2, 4);
coordinateVector = new CoordinateVector(-3, 1);
coordinate = new Coordinate(5, 3);
LineAlgorithms.Distance(lineStart, coordinateVector, coordinate).ShouldBe(0);
}