CMap Tables
A CMap specifies the mapping from character codes to character selectors and serves the role of a font encoding.
CMaps are usually fully embedded into the PDF document and obtained from it during reading. A CMap can also be defined by a PDF name object, where the name identifies a well-known predefined CMap. The list of predefined CMaps is available at https://github.com/adobe-type-tools/cmap-resources.
Working with Documents Containing Predefined CMap Tables
RadPdfProcessing enables you to use a default implementation for the known predefined CMap tables. You can also create a custom one if you encounter a specific scenario in which the resources are not available for the default class.
Default Implementation
The Telerik[.Windows].Documents.CMapUtils package provides a default implementation for obtaining the data of a predefined CMap table by a given name. The class that contains implementations for all the CMap tables defined by the PDF Format Specification is called PredefinedCMapsProvider. To register an instance of the default implementation, use the FixedExtensibilityManager class.
To use this feature, you must add a reference to the Telerik[.Windows].Documents.CMapUtils package.
Example 1: Register Default CMapsProvider
Telerik.Windows.Documents.Extensibility.FixedExtensibilityManager.PredefinedCMapsProvider = new PredefinedCMapsProvider();After you register the PredefinedCMapsProvider class, you can import any document containing a predefined CMap table.
Creating a Custom Implementation
The default implementation covers the majority of the scenarios but in some rare cases, you might need to provide a custom CMap. The API enables you to create a custom implementation for a CMap provider so you can provide the data for the custom CMap table. To achieve that, inherit the PredefinedCMapsProviderBase abstract class and implement the following members:
| Member | Description |
|---|---|
byte[] GetCidCMapData(string name) | Retrieves the character code to CID mapping of a predefined CMap. Returns the CMap resource data for the specified name. |
byte[] GetUnicodeCMapData(string name) | Retrieves the character code to Unicode mapping of a predefined CMap. Returns the CMap resource data for the specified name. |