Aspose.Diagram Font Operations

How to Specify TrueType Fonts Location

Aspose.Diagram lets developers to set the font directories for rendering in Visio diagrams. This article shows how to utilize fonts from custom directories.

Working with Fonts

Where Aspose.Diagram Looks for TrueType Fonts on Windows

Aspose.Diagram searches for fonts in the Windows\Fonts folder. This default setting works most of the time so only specify your own fonts folders if you really need to.

How to Explicitly Specify a Font Folder

Aspose.Diagram APIs has exposed FontDirs property for the Diagram class to specify the fonts folders as described below.

  1. The Diagram.FontDirs property accepts a string array so developer may specify many font directories using this approach.

Programming Sample

The code example below demonstrates how to set Aspose.Diagram to look in multiple folders for TrueType fonts when rendering or embedding fonts.

Receive Notification of Missing Fonts and Font Substitution during Rendering

Aspose.Diagram API requires access to the accurate font in order to properly render the drawing to PDF format. If the required font is not available on the machine, then Aspose.Diagram API renders any instance of that font using the default font or the closest available font on the machine, since this substitution can change the look of the rendered drawing, developers may need to be notified when a font is missing and with what font it will be replaced.

Notification of Missing Fonts and Font Substitution Programming Sample

To be notified of font substitution during rendering:

  1. Create a class that implements the IWarningCallback
  2. Pass it to the PdfSaveOptions.WarningCallback property.

During saving of the drawing the instance of IWarningCallback is called if there are any potential fidelity issues with the drawing. In this case, we choose to only process warnings that are of font substitution and print the warning to the screen. The below example demonstrates how to receive notifications of font substitutions by using IWarningCallback.


 // The path to the documents directory.

string dataDir = RunExamples.GetDataDir_Intro();

// load the document to render.

Diagram diagram = new Diagram(dataDir + "Drawing1.vsdx");

// initialize PdfSaveOptions object

PdfSaveOptions saveOp = new PdfSaveOptions();

// create a new class implementing IWarningCallback which collect any warnings produced during drawing save.

HandleDocumentWarnings callback = new HandleDocumentWarnings();

saveOp.WarningCallback = callback;

// pass the save options along with the save path to the save method.

diagram.Save(dataDir + "NotificationofMissingFonts_Out.pdf", saveOp);

Implementing the IWarningCallback

The last step is to create the class implementing the IWarningCallback interface. This class will print out any warnings of font substitution to the console. The below example demonstrates how to implement the IWarningCallback to be notified of any font substitution during document save.


 class HandleDocumentWarnings : IWarningCallback



    * Our callback only needs to implement the "Warning" method. This method is

    * called whenever there is a potential issue during document processing.

    * The callback can be set to listen for warnings generated during document

    * load and/or document save.


    public void Warning(WarningInfo info)


        // We are only interested in fonts being substituted.

        if (info.WarningType == WarningType.FontSubstitution)


            Console.WriteLine("Font substitution: " + info.Description);