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2 GDI printers 3 GDI+ 4 External link |
GDI is responsible for tasks such as drawing lines and curves, rendering fonts and handling palettes. It is not directly responsible for drawing windows, menus, etc.: that task is reserved for the user subsystem.
Perhaps the most significant capability of GDI over more direct methods of accessing the hardware is its scaling capabilities, and abstraction of target devices. Using GDI, it is very easy to draw on multiple devices, such as a screen and a printer, and expect proper reproduction in each case. This capability is at the centre of all WYSIWYG applications for Microsoft Windows.
Simple games which do not require fast graphics rendering, such as Freecell or Minesweeper, use GDI. However, for applications requiring more complex graphics, GDI is too slow. This is due to GDI's constant checking to make sure every pixel is inside the proper window, and also its complex driver model. Modern games use DirectX, which gives programmers near-direct access to the video hardware—for example, providing the address of the actual screen memory.
GDI printers, in particular GDI laser printers, replace the traditional processing power of the printer itself with capabilities "borrowed" from the host computer. There are two advantages:
In general, the cheapest current model laser printers are GDI devices. Most manufacturers also produce more flexible models that add PCL compatibility, or Postscript, or both. In most cases it is only the very cheapest models in any given manufacturer's range that are GDI only.
With the introduction of Windows XP, GDI was deprecated in favor of its successor, the C++ based GDI+ subsystem. GDI+ is a "next generation" 2D graphics environment, adding advanced features such as alpha blending, gradient shading, more complex path management, intrinsic support for modern graphics-file formats like JPEG and PNG (which were conspicuously absent in GDI), and general support for composition of affine transformations in the 2D view pipeline. Use of these features are apparent in Windows XP's user interface, and their presence in the basic graphics layer greatly simplifies implementations of vector-graphics systems such as flash or SVG.
GDI+ is similar (in purpose and structure) to Apple's "Quartz 2D" subsystem, and the open-source "libart".GDI
GDI printers
The disadvantages are that:
Most current model inkjet printers are GDI-based (largely for performance reasons, as the cost factor is primarily to do with lasers), but the trend is to add more flexibility: many offer Mac support and the Linux community has become increasingly good at making Linux drivers available. Some (notably Epson) often also offer a more traditional emulation as a fallback.GDI+