SetLineAlpha Method (GdPicturePDF)

In This Topic

Sets the transparency level (the current stroking alpha constant) for all subsequent stroking operations, means those with the defined Stroke parameter, like the DrawCircle method or the DrawRectangle method. This constant specifies the constant shape or constant opacity value. The initial value is set to 255.

The alpha constant parameter is one of the graphics state parameters. These parameters are initialized to their default values at the beginning of each page (see PDF Reference, Section "Graphics State").

Syntax

Visual Basic
C#
Delphi
JScript
Managed Extensions for C++
C++/CLI

'Declaration
 
Public Function SetLineAlpha( _
   ByVal Alpha As Byte _
) As GdPictureStatus

public GdPictureStatus SetLineAlpha( 
   byte Alpha
)

public function SetLineAlpha( 
    Alpha: Byte
): GdPictureStatus;

public function SetLineAlpha( 
   Alpha : byte
) : GdPictureStatus;

public: GdPictureStatus SetLineAlpha( 
   byte Alpha
)

public:
GdPictureStatus SetLineAlpha( 
   byte Alpha
)

Parameters

Alpha: A new value for the transparency level. Use the value between 0 (full transparency) and 255 (full opacity).

Return Value

A member of the GdPictureStatus enumeration. If the method has been successfully followed, then the return value is GdPictureStatus.OK.

We strongly recommend always checking this status first.

Remarks

This method is only allowed for use with non-encrypted documents.

Be aware also that graphics state parameters are initialized to their default values at the beginning of each page.

Example

How to set the transparency to be used when drawing various rectangles.

VB.NET
C#

Dim caption As String = "Example: SetLineAlpha"
Dim gdpicturePDF As New GdPicturePDF()
Dim status As GdPictureStatus = gdpicturePDF.NewPDF()
If status = GdPictureStatus.OK Then
    gdpicturePDF.SetOrigin(PdfOrigin.PdfOriginTopLeft)
    gdpicturePDF.SetMeasurementUnit(PdfMeasurementUnit.PdfMeasurementUnitMillimeter)
    If (gdpicturePDF.NewPage(210, 297) = GdPictureStatus.OK) AndAlso
       (gdpicturePDF.ResetGraphicsState() = GdPictureStatus.OK) AndAlso 'The default graphics state is set.
       (gdpicturePDF.SetLineWidth(3) = GdPictureStatus.OK) AndAlso
       (gdpicturePDF.SetLineColor(0, 0, 255) = GdPictureStatus.OK) AndAlso
       (gdpicturePDF.SetFillColor(0, 255, 255) = GdPictureStatus.OK) AndAlso
       (gdpicturePDF.DrawRectangle(70, 10, 60, 30, True, True) = GdPictureStatus.OK) AndAlso
       (gdpicturePDF.DrawRectangle(70, 80, 60, 30, True, True) = GdPictureStatus.OK) AndAlso
       (gdpicturePDF.DrawRectangle(70, 150, 60, 30, True, True) == GdPictureStatus.OK) AndAlso
       (gdpicturePDF.SetLineColor(255, 165, 0) = GdPictureStatus.OK) AndAlso
       (gdpicturePDF.SetFillColor(188, 143, 143) = GdPictureStatus.OK) AndAlso
       (gdpicturePDF.SetLineWidth(8) = GdPictureStatus.OK) AndAlso
       (gdpicturePDF.DrawRectangle(10, 25, 180, 40, True, True) = GdPictureStatus.OK) AndAlso
       (gdpicturePDF.SetLineAlpha(200) = GdPictureStatus.OK) AndAlso
       (gdpicturePDF.SetFillAlpha(200) = GdPictureStatus.OK) AndAlso
       (gdpicturePDF.DrawRectangle(10, 95, 180, 40, True, True) = GdPictureStatus.OK) AndAlso
       (gdpicturePDF.SetLineAlpha(100) == GdPictureStatus.OK) AndAlso
       (gdpicturePDF.SetFillAlpha(100) == GdPictureStatus.OK) AndAlso
       (gdpicturePDF.DrawRectangle(10, 165, 180, 40, True, True) == GdPictureStatus.OK) Then
        status = gdpicturePDF.SaveToFile("test_Lines.pdf")
        If status = GdPictureStatus.OK Then
            MessageBox.Show("The example has been followed successfully and the file has been saved.", caption)
        Else
            MessageBox.Show("The example has been followed successfully, but the file can't be saved. Status: " + status.ToString(), caption)
        End If
    Else
        MessageBox.Show("The example has not been followed successfully." + vbCrLf + "The last known status is " + gdpicturePDF.GetStat().ToString(), caption)
    End If
Else
    MessageBox.Show("The NewPDF() method has failed with the status: " + status.ToString(), caption)
End If
gdpicturePDF.Dispose()

string caption = "Example: SetLineAlpha";
GdPicturePDF gdpicturePDF = new GdPicturePDF();
GdPictureStatus status = gdpicturePDF.NewPDF();
if (status == GdPictureStatus.OK)
{
    gdpicturePDF.SetOrigin(PdfOrigin.PdfOriginTopLeft);
    gdpicturePDF.SetMeasurementUnit(PdfMeasurementUnit.PdfMeasurementUnitMillimeter);
    if ((gdpicturePDF.NewPage(210, 297) == GdPictureStatus.OK) &&
        (gdpicturePDF.ResetGraphicsState() == GdPictureStatus.OK) && //The default graphics state is set.
        (gdpicturePDF.SetLineWidth(3) == GdPictureStatus.OK) &&
        (gdpicturePDF.SetLineColor(0, 0, 255) == GdPictureStatus.OK) &&
        (gdpicturePDF.SetFillColor(0, 255, 255) == GdPictureStatus.OK) &&
        (gdpicturePDF.DrawRectangle(70, 10, 60, 30, true, true) == GdPictureStatus.OK) &&
        (gdpicturePDF.DrawRectangle(70, 80, 60, 30, true, true) == GdPictureStatus.OK) &&
        (gdpicturePDF.DrawRectangle(70, 150, 60, 30, true, true) == GdPictureStatus.OK) &&
        (gdpicturePDF.SetLineColor(255, 165, 0) == GdPictureStatus.OK) &&
        (gdpicturePDF.SetFillColor(188, 143, 143) == GdPictureStatus.OK) &&
        (gdpicturePDF.SetLineWidth(8) == GdPictureStatus.OK) &&
        (gdpicturePDF.DrawRectangle(10, 25, 180, 40, true, true) == GdPictureStatus.OK) &&
        (gdpicturePDF.SetLineAlpha(200) == GdPictureStatus.OK) &&
        (gdpicturePDF.SetFillAlpha(200) == GdPictureStatus.OK) &&
        (gdpicturePDF.DrawRectangle(10, 95, 180, 40, true, true) == GdPictureStatus.OK) &&
        (gdpicturePDF.SetLineAlpha(100) == GdPictureStatus.OK) &&
        (gdpicturePDF.SetFillAlpha(100) == GdPictureStatus.OK) &&
        (gdpicturePDF.DrawRectangle(10, 165, 180, 40, true, true) == GdPictureStatus.OK))
    {
        status = gdpicturePDF.SaveToFile("test_Lines.pdf");
        if (status == GdPictureStatus.OK)
            MessageBox.Show("The example has been followed successfully and the file has been saved.", caption);
        else
            MessageBox.Show("The example has been followed successfully, but the file can't be saved. Status: " + status.ToString(), caption);
    }
    else
        MessageBox.Show("The example has not been followed successfully.\nThe last known status is " + gdpicturePDF.GetStat().ToString(), caption);
}
else
    MessageBox.Show("The NewPDF() method has failed with the status: " + status.ToString(), caption);
gdpicturePDF.Dispose();

Reference

GdPicturePDF Class
GdPicturePDF Members
SetLineAlpha Method
SetFillColor(Byte,Byte,Byte) Method
SetLineColor(Byte,Byte,Byte) Method
DrawLine Method
DrawRectangle Method
RestoreGraphicsState Method