Font substitution for unavailable fonts

9 Sep 20245 minutes to read

When a font used in a PowerPoint presentation is unavailable in the environment where it is converted to image, then the library substitutes the ‘Microsoft Sans Serif’ as a default font for text rendering. This leads to a difference in text layouts of PowerPoint presentation and the converted image. To avoid this, the Essential Presentation library allows you to set an alternate font for the missing font used in the PowerPoint presentation.

NOTE

Font substitution for Unavailable fonts is not supported in UWP platform.

The following code sample demonstrates how to set a substitute font for a missing font while converting a PowerPoint presentation to image.

//Load the PowerPoint presentation and convert to image
using (IPresentation pptxDoc = Presentation.Open("Sample.pptx"))
{
    //Initialize the PresentationRenderer to perform image conversion.
    pptxDoc.PresentationRenderer = new PresentationRenderer();
    // Initializes the 'SubstituteFont' event to set the replacement font
    pptxDoc.FontSettings.SubstituteFont += FontSettings_SubstituteFont;
    //Convert PowerPoint slide to image as stream.
    using (Stream stream = pptxDoc.Slides[0].ConvertToImage(ExportImageFormat.Jpeg))
    {
        //Create the output image file stream
        using (FileStream fileStreamOutput = File.Create("Output.jpg"))
        {
         //Copy the converted image stream into created output stream
         stream.CopyTo(fileStreamOutput);
        }
     }        
}
/// <summary>
/// Sets the alternate font when a specified font is unavailable in the production environment
/// </summary>
/// <param name="sender">FontSettings type of the Presentation in which the specified font is used but unavailable in production environment. </param>
/// <param name="args">Retrieves the unavailable font name and receives the substitute font name for conversion. </param>
private static void FontSettings_SubstituteFont(object sender, SubstituteFontEventArgs args)
{
    if (args.OriginalFontName == "Arial Unicode MS")

        args.AlternateFontName = "Arial";
    else
        args.AlternateFontName = "Times New Roman";
}
//Load the PowerPoint presentation and convert to image
using (IPresentation pptxDoc = Presentation.Open("Sample.pptx"))
{
    //Initialize 'ChartToImageConverter' to convert charts in the slides, and this is optional
    pptxDoc.ChartToImageConverter = new ChartToImageConverter();
    // Initializes the 'SubstituteFont' event to set the replacement font
    pptxDoc.FontSettings.SubstituteFont += FontSettings_SubstituteFont;
    //Converts the first slide into image
    Image image = pptxDoc.Slides[0].ConvertToImage(Syncfusion.Drawing.ImageType.Metafile);
    //Saves the image as file
    image.Save("slide1.png");
    //Disposes the image
    image.Dispose();
}
/// <summary>
/// Sets the alternate font when a specified font is unavailable in the production environment
/// </summary>
/// <param name="sender">FontSettings type of the Presentation in which the specified font is used but unavailable in production environment. </param>
/// <param name="args">Retrieves the unavailable font name and receives the substitute font name for conversion. </param>
private static void FontSettings_SubstituteFont(object sender, SubstituteFontEventArgs args)
{
    if (args.OriginalFontName == "Arial Unicode MS")
        args.AlternateFontName = "Arial";
    else
        args.AlternateFontName = "Times New Roman";
}
'Load the PowerPoint presentation and convert to image
Dim pptxDoc As IPresentation = Presentation.Open("Sample.pptx")
'Initialize 'ChartToImageConverter' to convert charts in the slides, and this is optional
pptxDoc.ChartToImageConverter = New ChartToImageConverter()
'Initializes the 'SubstituteFont' event to set the replacement font
AddHandler pptxDoc.FontSettings.SubstituteFont, AddressOf SubstituteFont
'Convert the PowerPoint presentation to image.
Dim image As Image = pptxDoc.Slides(0).ConvertToImage(Syncfusion.Drawing.ImageType.Metafile)
'Save the image.
image.Save("slide1.png")
'Dispose the Presentation instance
pptxDoc.Dispose()
'Dispose the image
image.Dispose()
''' <summary>
''' Sets the alternate font when a specified font is unavailable in the production environment
''' </summary>
''' <param name="sender">FontSettings type of the Presentation in which the specified font is used but unavailable in production environment. </param>
''' <param name="args">Retrieves the unavailable font name and receives the substitute font name for conversion. </param>
Private Sub SubstituteFont(ByVal sender As Object, ByVal args As SubstituteFontEventArgs)
    ' Sets the alternate font when a specified font is not installed in the production environment
    If args.OriginalFontName = "Arial Unicode MS" Then
        args.AlternateFontName = "Arial"
    Else
        args.AlternateFontName = "Times New Roman"
    End If
End Sub

You can download a complete working sample from GitHub.