Fallback fonts in Word to Image conversion

29 Nov 202415 minutes to read

During Word to image conversions, if a glyph of the input text is unavailable in the specified font, the text will not be rendered properly. To address this, the Syncfusion® Word (DocIO) library allows users to specify fallback fonts. When a glyph is missing, the library will use one of the fallback fonts to render the text correctly in the output image.

Users can configure fallback fonts in the following ways:

  • Initialize default fallback fonts.
  • Set custom fonts as fallback fonts for specific script types, including Arabic, Hebrew, Chinese, Japanese, and more.
  • Set custom fonts as fallback fonts for a particular range of Unicode text.

NOTE

DocIO internally uses user-initialized or specified fallback fonts for Unicode characters during Word to Image conversion. Therefore, the specified fallback fonts must be installed in the production environment or embedded in the input Word document (DOCX). Otherwise, it will not render the text properly using the fallback fonts.

Initialize default fallback fonts

The following code example demonstrates how to initialize a default fallback fonts while converting a Word document to an Image. The InitializeDefault API sets the default fallback fonts for specific script types like Arabic, Hebrew, Chinese, Japanese etc.

//Opens the file as stream.
using (FileStream inputStream = new FileStream("Template.docx", FileMode.Open, FileAccess.Read))
{
   //Loads an existing Word document file stream.
   using (WordDocument wordDocument = new WordDocument(inputStream, Syncfusion.DocIO.FormatType.Docx))
   {
      //Initialize the default fallback fonts collection.
      wordDocument.FontSettings.FallbackFonts.InitializeDefault();
      //Instantiation of DocIORenderer for Word to image conversion.
      using (DocIORenderer render = new DocIORenderer())
      {
         //Convert the entire Word document to images.
         Stream[] imageStreams = wordDocument.RenderAsImages(); 
         int i = 0;
         foreach (Stream stream in imageStreams)
         {
             //Reset the stream position.
             stream.Position = 0;
             //Save the stream as file.
             using (FileStream fileStreamOutput = File.Create("WordToImage_" + i + ".jpeg"))
             {
                stream.CopyTo(fileStreamOutput);
             }
             i++;
         }
      }
   }
}

You can download a complete working sample from GitHub.

Fallback fonts based on script type

The following code example demonstrates how a user can add fallback fonts based on the script types, which DocIO considers internally when converting a Word document to an Image.

//Opens the file as stream.
using (FileStream inputStream = new FileStream("Template.docx", FileMode.Open, FileAccess.Read))
{
   //Loads an existing Word document file stream.
   using (WordDocument wordDocument = new WordDocument(inputStream, Syncfusion.DocIO.FormatType.Docx))
   {
      //Adds fallback font for "Arabic" script type.
      wordDocument.FontSettings.FallbackFonts.Add(ScriptType.Arabic, "Arial, Times New Roman");
      //Adds fallback font for "Hebrew" script type.
      wordDocument.FontSettings.FallbackFonts.Add(ScriptType.Hebrew, "Arial, Courier New");
      //Adds fallback font for "Hindi" script type.
      wordDocument.FontSettings.FallbackFonts.Add(ScriptType.Hindi, "Mangal, Nirmala UI");
      //Adds fallback font for "Chinese" script type.
      wordDocument.FontSettings.FallbackFonts.Add(ScriptType.Chinese, "DengXian, MingLiU");
      //Adds fallback font for "Japanese" script type.
      wordDocument.FontSettings.FallbackFonts.Add(ScriptType.Japanese, "Yu Mincho, MS Mincho");
      //Adds fallback font for "Thai" script type.
      wordDocument.FontSettings.FallbackFonts.Add(ScriptType.Thai, "Tahoma, Microsoft Sans Serif");
      //Adds fallback font for "Korean" script type.
      wordDocument.FontSettings.FallbackFonts.Add(ScriptType.Korean, "Malgun Gothic, Batang");
      //Instantiation of DocIORenderer for Word to image conversion.
      using (DocIORenderer render = new DocIORenderer())
      {
         //Convert the entire Word document to images.
         Stream[] imageStreams = wordDocument.RenderAsImages(); 
         int i = 0;
         foreach (Stream stream in imageStreams)
         {
             //Reset the stream position.
             stream.Position = 0;
             //Save the stream as file.
             using (FileStream fileStreamOutput = File.Create("WordToImage_" + i + ".jpeg"))
             {
                 stream.CopyTo(fileStreamOutput);
             }
             i++;
         }
      }
   }
}

You can download a complete working sample from GitHub.

Fallback fonts for range of Unicode text

Users can set fallback fonts for specific Unicode range of text to be used in Word to Image conversion.

The following code example demonstrates how users can add fallback fonts by using a specific Unicode range of text that DocIO considers internally while converting a Word document to an image.

//Opens the file as stream.
using (FileStream inputStream = new FileStream("Template.docx", FileMode.Open, FileAccess.Read))
{
   //Loads an existing Word document file stream.
   using (WordDocument wordDocument = new WordDocument(inputStream, Syncfusion.DocIO.FormatType.Docx))
   {
      //Adds fallback font for "Arabic" specific unicode range.
      wordDocument.FontSettings.FallbackFonts.Add(new FallbackFont(0x0600, 0x06ff, "Arial"));
      //Adds fallback font for "Hebrew" specific unicode range.
      wordDocument.FontSettings.FallbackFonts.Add(new FallbackFont(0x0590, 0x05ff, "Times New Roman"));
      //Adds fallback font for "Hindi" specific unicode range.
      wordDocument.FontSettings.FallbackFonts.Add(new FallbackFont(0x0900, 0x097F, "Nirmala UI"));
      //Adds fallback font for "Chinese" specific unicode range.
      wordDocument.FontSettings.FallbackFonts.Add(new FallbackFont(0x4E00, 0x9FFF, "DengXian"));
      //Adds fallback font for "Japanese" specific unicode range.
      wordDocument.FontSettings.FallbackFonts.Add(new FallbackFont(0x3040, 0x309F, "MS Gothic"));
      //Adds fallback font for "Thai" specific unicode range.
      wordDocument.FontSettings.FallbackFonts.Add(new FallbackFont(0x0E00, 0x0E7F, "Tahoma"));
      //Adds fallback font for "Korean" specific unicode range.
      wordDocument.FontSettings.FallbackFonts.Add(new FallbackFont(0xAC00, 0xD7A3, "Malgun Gothic"));
      //Instantiation of DocIORenderer for Word to Image conversion.
      using (DocIORenderer render = new DocIORenderer())
      {
         //Convert the entire Word document to images.
         Stream[] imageStreams = wordDocument.RenderAsImages(); 
         int i = 0;
         foreach (Stream stream in imageStreams)
         {
             //Reset the stream position.
             stream.Position = 0;
             //Save the stream as file.
             using (FileStream fileStreamOutput = File.Create("WordToImage_" + i + ".jpeg"))
             {
                 stream.CopyTo(fileStreamOutput);
             }
             i++;
         }
      }
   }
}

You can download a complete working sample from GitHub.

Modify the exiting fallback fonts

The following code example demonstrates how user can modify or customize the existing fallback fonts using FontNames API while converting a Word document to an Image.

//Opens the file as stream.
using (FileStream inputStream = new FileStream("Template.docx", FileMode.Open, FileAccess.Read))
{
   //Loads an existing Word document file stream.
   using (WordDocument wordDocument = new WordDocument(inputStream, Syncfusion.DocIO.FormatType.Docx))
   {
      //Initialize the default fallback fonts collection.
      wordDocument.FontSettings.FallbackFonts.InitializeDefault();
      FallbackFonts fallbackFonts = wordDocument.FontSettings.FallbackFonts;
      foreach (FallbackFont fallbackFont in fallbackFonts) 
      {
         //Customize a default fallback font name as "David" for the Hebrew script.
         if (fallbackFont.ScriptType == ScriptType.Hebrew)
            fallbackFont.FontNames = "David";
         //Customize a default fallback font name as "Microsoft Sans Serif" for the Thai script.
         else if (fallbackFont.ScriptType == ScriptType.Thai)
            fallbackFont.FontNames = "Microsoft Sans Serif";
      }
      //Instantiation of DocIORenderer for Word to Image conversion.
      using (DocIORenderer render = new DocIORenderer())
      {
         //Convert the entire Word document to images.
         Stream[] imageStreams = wordDocument.RenderAsImages(); 
         int i = 0;
         foreach (Stream stream in imageStreams)
         {
             //Reset the stream position.
             stream.Position = 0;
             //Save the stream as file.
             using (FileStream fileStreamOutput = File.Create("WordToImage_" + i + ".jpeg"))
             {
                 stream.CopyTo(fileStreamOutput);
             }
             i++;
         }
      }
   }
}

You can download a complete working sample from GitHub.

Supported script types

The following table illustrates the supported script types by the .NET Word library (DocIO) in Word to Image conversion.

Script types Ranges Default fallback fonts considered in InitializeDefault() API
Arabic 0x0600 - 0x06ff
0x0750 - 0x077f
0x08a0 - 0x08ff
0xfb50 - 0xfdff
0xfe70 - 0xfeff
 Arial, Times New Roman, Microsoft Uighur
Hebrew 0x0590 - 0x05ff
0xfb1d - 0xfb4f
 Arial, Times New Roman, David
Hindi 0x0900 - 0x097F
0xa8e0 - 0xa8ff
0x1cd0 - 0x1cff
 Mangal, Utsaah
Chinese 0x4E00 - 0x9FFF
0x3400 - 0x4DBF
0xd840 - 0xd869
0xdc00 - 0xdedf
0xA960 - 0xA97F
0xFF00 - 0xFFEF
0x3000 - 0x303F
 DengXian, MingLiU, MS Gothic
Japanese 0x30A0 - 0x30FF
0x3040 - 0x309F
 Yu Mincho, MS Mincho
Thai 0x0E00 - 0x0E7F Tahoma, Microsoft Sans Serif
Korean 0xAC00 - 0xD7A3
0x1100 - 0x11FF
0x3130 - 0x318F
0xA960 - 0xA97F
0xD7B0 - 0xD7FF
0xAC00 - 0xD7AF
 Malgun Gothic, Batang

NOTE

  1. In Azure Web Service and Azure APP Service, .NET GDI+ (System.Drawing) does not support the Metafile image (vector image). So, the image will be generated as Bitmap (raster image).
  2. Creating an instance of the ChartToImageConverter class is mandatory to convert the charts present in the Word document to Image. Otherwise, the charts are not preserved in the generated image.
  3. Total number of images may vary based on unsupported elements in the input Word document.
  4. Word to Image conversion has the same limitations and unsupported elements of Word to PDF conversion.
  5. Different styles of borders are known limitations in Word to Image conversion in ASP.NET Core, Xamarin, Blazor, WinUI, and .NET MAUI platforms.
  6. In ASP.NET Core, Blazor, Xamarin, WinUI and .NET MAUI platforms, to convert Word document to images we recommend you to use Word to image assemblies or NuGet as a reference in your application.
  7. DocIO supports Word to image conversion in UWP application using DocIORenderer.
  8. In addition to the previous NuGet packages, we recommend to use SkiaSharp.NativeAssets.Linux v2.88.8 and HarfBuzzSharp.NativeAssets.Linux v7.3.0.2 NuGets to perform Word to Image conversion in Linux environment.
  9. The .NET Word Library (DocIO) uses System.Drawing functionalities for Word to image conversion in .NET Framework applications. And System.Drawing itself uses a fallback font to preserve the Unicode text while drawing the text in the image. So, these Fallback fonts APIs are not supported in .NET Framework.