The .NET Compact Framework provides programs with support for creating graphical output. We prefer using .NET Compact Framework classes whenever possible. To accomplish something beyond what the .NET Compact Framework supports, however, we drill through the managed-code layer to the underlying Win32 API substrate. This tip from Informit provides a brief introduction to working with graphics in the .NET Compact Framework.
In general, programs do not create graphical output by drawing directly to device hardware. A program typically calls a library of graphical output functions. Those drawing functions, in turn, rely on device drivers that provide the device-specific elements needed to create output on a device. Historically, creating output on a graphic device such as a display screen or a printer involves these software layers:
- Drawing program
- Graphic function library
- Graphic device driver (display driver or printer driver)
The core graphics library on desktop Windows is the Graphics Device Interface (GDI, gdi32.dll). With the coming of .NET, Microsoft added a second library (GDI+, gdiplus.dll) to supplement GDI drawing support. This second library provides a set of enhancements on top of the core GDI drawing functions. While the primary role for GDI+ was to support graphics for the managed-code library, it also provides a nice bonus for native-mode application programmers: the library can be called from unmanaged (native-mode) C++ programs. On the desktop, these two graphic libraries—GDI and GDI+—provide the underpinnings for all of the .NET graphic classes. And so, with .NET Framework programs running on the Windows desktop, the architecture of graphical output involves the following elements:
- Managed-code program
- Shared managed-code library (System.Drawing.dll)
- GDI+ native-code library (gdiplus.dll)
- GDI native-code library (gdi32.dll)
- Graphic device driver (display driver or printer driver)
Windows CE supports a select set of GDI drawing functions. There is no library explicitly named GDI in Windows CE. Instead, the graphical output functions reside in the coredll.dll library. These functions are exactly like their desktop counterparts, so even if there is no library named GDI in Windows CE, we refer to these functions as GDI functions.
More information on the working with graphics in the .NET Compact Framework is available at Informit.
