1.3.1 Accelerated Graphics

The remoting of graphics images (see [MS-RDPBCGR] sections 2.2.9.1.1.3.1.2 and 2.2.9.1.2.1.2) is accomplished by continuously sending updated bitmap images from server to client. Even though these bitmaps can be compressed, it is still not a bandwidth-efficient mechanism to employ, especially when dealing with graphics-intensive applications that refresh regularly.

The Remote Desktop Protocol: GDI Acceleration Extension aims to reduce the bandwidth associated with graphics remoting by encoding the drawing operations that produce an image instead of encoding the actual image.

For example, instead of sending the bitmap image of a filled rectangle from server to client, an order to render a rectangle at coordinate (X, Y) with a given width, height, and fill color is sent to the client. The client then executes the drawing order to produce the intended graphics result.

In addition to defining how to encode common drawing operations, the Remote Desktop Protocol: GDI Acceleration Extension also facilitates the use of caches to store drawing primitives such as bitmaps, color tables, and characters. The effective use of caching techniques helps to reduce wire traffic by ensuring that items used in multiple drawing operations are sent only once from server to client (retransmission of these items for use in conjunction with future drawing operations is not required after the item has been cached on the client).

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