Stroke.SelfIntersections Property

Stroke.SelfIntersections Property

Gets the self-intersections of the Stroke object.

Definition

Visual Basic .NET	Public ReadOnly Property SelfIntersections As Single()
C#	public float[] SelfIntersections { get; }
Managed C++	public: __property float* get_SelfIntersections();

Property Value

System.Single[]. An array of floating point index values that represents the self-intersections of a Stroke object.

This property is read-only. This property has no default value.

Remarks

A self-intersection is the point of a stroke where the stroke crosses over itself.

A floating point index is a float value that represents a location somewhere between two points in the stroke. As examples, if 0.0 is the first point in the stroke and 1.0 is the second point in the stroke, 0.5 is halfway between the first and second points. Similarly, a floating point index value of 37.25 represents a location that is 25 percent along the line between points 37 and 38 of the stroke.

Note: A floating point index is returned for each intersection and line segment combination. If a stroke has one intersection, the SelfIntersections property will return two self intersections, one for each line segment that is part of the intersection.

Examples

[C#]

This C# example demonstrates several kinds of information that is recorded with each Stroke object. The calling program uses menu items to toggle the display of each stroke's points, polyline cusps, Bezier points, Bezier cusps, and self-intersections. The Renderer object's InkSpaceToPixel method is used to convert the points for display. The LocatePoint method is used to interpolate the locations of the self-intersections.

Microsoft.Ink.InkCollector theInkCollector;

// Event handler for the form's load event.
private void Form1_Load(object sender, System.EventArgs e)
{
    // Create the InkCollector.
    theInkCollector = new InkCollector(this.Handle);

    // Attach an event handler for the Stroke event.
    theInkCollector.Stroke += new InkCollectorStrokeEventHandler(theInkCollector_Stroke);

    // Enable the InkCollector.
    theInkCollector.Enabled = true;
}

// Event handler for the InkCollector's Stroke event.
private void theInkCollector_Stroke(object sender, InkCollectorStrokeEventArgs e)
{
    // Force the form to repaint.
    Refresh();
}

// Event handler for the Clear menu's Click event.
private void menuClear_Click(object sender, System.EventArgs e)
{
    // Delete the strokes in the InkCollector.
    theInkCollector.Ink.DeleteStrokes();

    // Force the form to repaint.
    Refresh();
}

private void menuExit_Click(object sender, System.EventArgs e)
{
    this.Close();
}

// Event handler for the Click event for subitems of the Display menu.
private void menuDisplayItem_Click(object sender, System.EventArgs e)
{
    // Check each subitem to see if it was clicked.
    foreach (System.Windows.Forms.MenuItem menu in menuDisplay.MenuItems)
    {
        if (sender == menu)
        {
            // Toggle the menu item's checked property.
            menu.Checked = !menu.Checked;
        }
    }

    // Force the form to repaint.
    this.Refresh();
}

// Event handler for the form's Paint event.
private void Form1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{
    Graphics g = e.Graphics;

    // Highlight specific points or cusps of each stroke.
    Strokes theStrokes = theInkCollector.Ink.Strokes;
    foreach (Stroke theStroke in theStrokes)
    {
        // Convert the stroke's points and Bezier points from ink space to pixel coordinates.
        Point [] ptBezierPoints = theStroke.BezierPoints;
        Point [] ptStrokePoints = theStroke.GetPoints();
        theInkCollector.Renderer.InkSpaceToPixel(g, ref ptBezierPoints);
        theInkCollector.Renderer.InkSpaceToPixel(g, ref ptStrokePoints);

        // If all points is checked, highlight the points of the stroke.
        if (menuAllPoints.Checked)
        {
            foreach (Point pt in ptStrokePoints)
            {
                // draw a little diagonal line from each point
                g.DrawEllipse(Pens.Magenta, pt.X-2, pt.Y-2, 4, 4);
            }
        }

        // If polyline cusps is checked, highlight the cusps of the stroke.
        if (menuPolylineCusps.Checked)
        {
            int[] theCusps = theStroke.PolylineCusps;
            foreach (int i in theCusps)
            {
                // Draw a little rectangle around each polyline cusp.
                g.DrawEllipse(Pens.BlueViolet, ptStrokePoints[i].X - 3, ptStrokePoints[i].Y - 3, 6, 6);
            }
        }

        // If Bezier points is checked, highlight the Bezier points of the stroke.
        if (menuBezierPoints.Checked)
        {
            foreach (Point pt in ptBezierPoints)
            {
                // Draw a little diagonal line from each Bezier point.
                g.DrawEllipse(Pens.Goldenrod, pt.X-4, pt.Y-4, 8, 8);
            }
        }

        // If Bezier cusps is checked, highlight the Bezier cusps of the stroke.
        if (menuBezierCusps.Checked)
        {
            int [] theCusps = theStroke.BezierCusps;
            foreach (int i in theCusps)
            {
                // Draw a little rectangle around each Bezier cusp.
                g.DrawEllipse(Pens.Blue,
                    ptBezierPoints[i].X-5, ptBezierPoints[i].Y-5, 10, 10);
            }
        }

        // If self intersections is checked, highlight the self intersections of the stroke.
        if (menuSelfIntersections.Checked)
        {
            float [] theSelfIntersectionLocationsArray = theStroke.SelfIntersections;
            foreach (float f in theSelfIntersectionLocationsArray)
            {
                Point pt = LocatePoint(theStroke, f);
                theInkCollector.Renderer.InkSpaceToPixel(g, ref pt);
                // Draw a little circle around each intersection.
                g.DrawEllipse(Pens.Red, pt.X-7, pt.Y-7, 14, 14);
            }
        }
    }
}

// This function returns the approximate point along
// a stroke represented by a float, as a Point.
private Point LocatePoint(Stroke theStroke, float theFIndex)
{
    // Get the two nearest points to the point of interest.
    Point [] ptStrokePoints = theStroke.GetPoints((int)Math.Floor(theFIndex), 2);

    // Get fractional part to interpolate the distance between the points.
    float theFraction = theFIndex - (float)Math.Floor(theFIndex);
    int deltaX = (int)((ptStrokePoints[1].X - ptStrokePoints[0].X) * theFraction);
    int deltaY = (int)((ptStrokePoints[1].Y - ptStrokePoints[0].Y) * theFraction);

    // Return the interpolated point.
    return new Point(ptStrokePoints[0].X + deltaX, ptStrokePoints[0].Y + deltaY);
}

[Visual Basic .NET]

This Microsoft® Visual Basic® .NET example demonstrates several kinds of information that is recorded with each Stroke object. The calling program uses menu items to toggle the display of each stroke's points, polyline cusps, Bezier points, Bezier cusps, and self-intersections. The Renderer object's InkSpaceToPixel method is used to convert the points for display. The LocatePoint method is used to interpolate the locations of the self-intersections.

Dim WithEvents theInkCollector As Microsoft.Ink.InkCollector

' Event handler for the form's Load event.
Private Sub Form1_Load(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles MyBase.Load

    ' Create and enable the InkCollector
    theInkCollector = New Microsoft.Ink.InkCollector(Me.Handle)
    theInkCollector.Enabled = True

    ' Associate the Click event handler with subitems of the Display menu.
    AddHandler menuAllPoints.Click, AddressOf menuDisplayItem_Click
    AddHandler menuPolylineCusps.Click, AddressOf menuDisplayItem_Click
    AddHandler menuBezierPoints.Click, AddressOf menuDisplayItem_Click
    AddHandler menuBezierCusps.Click, AddressOf menuDisplayItem_Click
    AddHandler menuSelfIntersections.Click, AddressOf menuDisplayItem_Click
End Sub

' Event handler for the InkCollector's Stroke event.
Private Sub theInkCollector_Stroke(ByVal sender As Object, _
    ByVal e As Microsoft.Ink.InkCollectorStrokeEventArgs) Handles theInkCollector.Stroke

    ' Force the form to repaint.
    Me.Refresh()
End Sub

' Event handler for the Clear menu's Click event.
Private Sub menuClear_Click(ByVal sender As Object, _
    ByVal e As System.EventArgs) Handles menuClear.Click

    ' Delete the strokes in the InkCollector.
    theInkCollector.Ink.DeleteStrokes()

    ' Force the form to repaint.
    Me.Refresh()
End Sub

' Event handler for the Click event for subitems of the Display menu.
Private Sub menuDisplayItem_Click(ByVal sender As Object, _
    ByVal e As System.EventArgs)

    ' Check each subitem to see if it was clicked.
    For Each menu As System.Windows.Forms.MenuItem In menuDisplay.MenuItems
        If (sender Is menu) Then
            ' Toggle the menu item's checked property.
            menu.Checked = Not menu.Checked
        End If
    Next

    ' Force the form to repaint.
    Me.Refresh()
End Sub

' Event handler for the form's Paint event.
Private Sub Form1_Paint(ByVal sender As Object, _
    ByVal e As System.Windows.Forms.PaintEventArgs) Handles MyBase.Paint

    Dim g As Graphics = e.Graphics

    ' Highlight specific points or cusps of each stroke.
    Dim theStrokes As Microsoft.Ink.Strokes = theInkCollector.Ink.Strokes
    For Each theStroke As Microsoft.Ink.Stroke In theStrokes

        ' Convert the stroke's points and Bezier points from ink space to pixel coordinates.
        Dim ptBezierPoints() As Point = theStroke.BezierPoints
        Dim ptStrokePoints() As Point = theStroke.GetPoints()
        theInkCollector.Renderer.InkSpaceToPixel(g, ptBezierPoints)
        theInkCollector.Renderer.InkSpaceToPixel(g, ptStrokePoints)

        ' If all points is checked, highlight the points of the stroke.
        If (menuAllPoints.Checked) Then
            For Each pt As Point In ptStrokePoints
                ' draw a little diagonal line from each point
                g.DrawEllipse(Pens.Magenta, pt.X - 2, pt.Y - 2, 4, 4)
            Next
        End If

        ' If polyline cusps is checked, highlight the cusps of the stroke.
        If (menuPolylineCusps.Checked) Then
            Dim theCusps() As Integer = theStroke.PolylineCusps
            For Each i As Integer In theCusps
                ' Draw a little rectangle around each polyline cusp.
                g.DrawEllipse(Pens.BlueViolet, ptStrokePoints(i).X - 3, ptStrokePoints(i).Y - 3, 6, 6)
            Next
        End If

        ' If Bezier points is checked, highlight the Bezier points of the stroke.
        If (menuBezierPoints.Checked) Then
            For Each pt As Point In ptBezierPoints
                ' Draw a little diagonal line from each Bezier point.
                g.DrawEllipse(Pens.Goldenrod, pt.X - 4, pt.Y - 4, 8, 8)
            Next
        End If

        ' If Bezier cusps is checked, highlight the Bezier cusps of the stroke.
        If (menuBezierCusps.Checked) Then
            Dim theCusps() As Integer = theStroke.BezierCusps
            For Each i As Integer In theCusps
                ' Draw a little rectangle around each Bezier cusp.
                g.DrawEllipse(Pens.Blue, ptBezierPoints(i).X - 5, ptBezierPoints(i).Y - 5, 10, 10)
            Next
        End If

        ' If self intersections is checked, highlight the self intersections of the stroke.
        If (menuSelfIntersections.Checked) Then
            Dim theSelfIntersectionLocationsArray() As Single = theStroke.SelfIntersections
            For Each f As Single In theSelfIntersectionLocationsArray
                Dim pt As Point = LocatePoint(theStroke, f)
                theInkCollector.Renderer.InkSpaceToPixel(g, pt)
                ' Draw a little circle around each intersection.
                g.DrawEllipse(Pens.Red, pt.X - 7, pt.Y - 7, 14, 14)
            Next
        End If
    Next
End Sub

' This function returns the approximate point along
' a stroke represented by a float, as a Point.
Private Function LocatePoint(ByVal theStroke As Microsoft.Ink.Stroke, _
    ByVal theFIndex As Single) As Point

    ' Get the two nearest points to the point of interest.
    Dim ptStrokePoints() As Point = theStroke.GetPoints(Math.Floor(theFIndex), 2)

    ' Get fractional part to interpolate the distance between the points.
    Dim theFraction As Single = theFIndex - Math.Floor(theFIndex)
    Dim deltaX As Integer = (ptStrokePoints(1).X - ptStrokePoints(0).X) * theFraction
    Dim deltaY As Integer = (ptStrokePoints(1).Y - ptStrokePoints(0).Y) * theFraction

    ' Return the interpolated point.
    LocatePoint = New Point(ptStrokePoints(0).X + deltaX, ptStrokePoints(0).Y + deltaY)
End Function