Gets a resource from the resources dictionary.
Resources are cached for fast lookup of repeated requests.
The ResourceType enumeration may take the following values:
- ExtGState - External graphics states.
- ColorSpace - Color space for graphics.
- Pattern - Pattern for filling areas.
- Shading - Shading type for filling areas.
- XObject - Encapsulated image in raster or vector form.
- Font - Font typeface for drawing text.
- ProcSet - Predefined procedure sets. This property is
deprecated in the PDF specification.
- Properties - Marked content properties.