How to implement FontsProvider
| Product Version | Product | Author |
|---|---|---|
| 2023.3.1106 | PdfProcessing | Yoan Karamanov |
Description
This article describes how to implement a FontsProvider in .NET Standard due to font limitations in PdfProcessing.
PdfProcessing needs to have access to the font data so that it can read it and add it to the PDF file. The .NET Standard version of the library does not offer a default mechanism to do that which is why, to allow the library to create and use fonts, an implementation of the FontsProviderBase abstract class needs to be provided and set to the FontsProvider property of the FixedExtensibilityManager.
Solution
You must know the fonts the PDF file contains beforehand. Then all fonts must be manually added to the implementation in a similar pattern in order to obtain each font file. Through validation, the corresponding font files are extracted.
In the validation, each font name (FontFamilyName) must be explicitly specified (e.g. "Calibri", "Century Gothic") along with the different font styles (e.g. "Italic", "Bold", "Bold Italic"). Depending on the combination of the font name and font properties a corresponding font file is obtained. The font file names must also be manually specified and known beforehand because each font has a different naming convention which cannot be predicted or automated (e.g. "calibriz - gothicbi" - both used for the Bold Italic style).
If the FontsProvider property is not set, a default font will be used when exporting the document.
Creating custom implementation by inheriting the FontsProviderBase abstract class
public class FontsProvider : Telerik.Windows.Documents.Extensibility.FontsProviderBase
{
public override byte[] GetFontData(Telerik.Windows.Documents.Core.Fonts.FontProperties fontProperties)
{
string fontFileName = fontProperties.FontFamilyName + ".ttf";
string fontFolder = Environment.GetFolderPath(Environment.SpecialFolder.Fonts);
//The fonts can differ depending on the file
if (fontProperties.FontFamilyName == "Calibri")
{
if (fontProperties.FontStyle == FontStyles.Italic && fontProperties.FontWeight == FontWeights.Bold)
{
fontFileName = $"calibriz.ttf";
}
else if (fontProperties.FontStyle == FontStyles.Italic)
{
fontFileName = $"calibrii.ttf";
}
else if (fontProperties.FontWeight == FontWeights.Normal)
{
fontFileName = "calibri.ttf";
}
else if (fontProperties.FontWeight == FontWeights.Bold)
{
fontFileName = $"calibrib.ttf";
}
}
else if (fontProperties.FontFamilyName == "Century Gothic")
{
if (fontProperties.FontStyle == FontStyles.Italic && fontProperties.FontWeight == FontWeights.Bold)
{
fontFileName = $"gothicbi.ttf";
}
else if (fontProperties.FontStyle == FontStyles.Italic)
{
fontFileName = $"gothici.ttf";
}
else if (fontProperties.FontWeight == FontWeights.Normal)
{
fontFileName = "gothic.ttf";
}
else if (fontProperties.FontWeight == FontWeights.Bold)
{
fontFileName = $"gothicb.ttf";
}
}
else if (fontProperties.FontFamilyName == "Wingdings")
{
if (fontProperties.FontWeight == FontWeights.Normal)
{
fontFileName = $"wingding.ttf";
}
}
//...add more fonts if needed...
DirectoryInfo directory = new DirectoryInfo(fontFolder);
FileInfo[] fontFiles = directory.GetFiles();
var fontFile = fontFiles.FirstOrDefault(f => f.Name.Equals(fontFileName, StringComparison.InvariantCultureIgnoreCase));
if (fontFile != null)
{
var targetPath = fontFile.FullName;
using (FileStream fileStream = File.OpenRead(targetPath))
{
using (MemoryStream memoryStream = new MemoryStream())
{
fileStream.CopyTo(memoryStream);
return memoryStream.ToArray();
}
}
}
return null;
}
}
Set the custom implementation inheriting the FontsProviderBase abstract class
Telerik.Windows.Documents.Extensibility.FontsProviderBase fontsProvider = new FontsProvider();
Telerik.Windows.Documents.Extensibility.FixedExtensibilityManager.FontsProvider = fontsProvider;