The MCGA Engine

Having largly discussed the history and conceptual development behind both graphics engines in other sections (see the development history), I will largly confine this page to a description of the engines capabilites and uses. The engine is available for download as the MCGA Toolkit, which contains the basic MCGA graphics engine, GraphV1.Pas (and its compiled version, GraphV1.tpu), and the imaging engine Images31.Pas in a source and compiled state. These units are in turn reliant upon the third party EMS and XMS memory engines, full description of which can be found in the tools section, notably the units entitled XMSLib and EMS. To link the engine to your program, simply invoke the graphics engine and the images engine, if required, in your uses statement. The engines are relatively compact, and your only memory considerations should be those required for the image buffers. The graphics engine can be invoked with two simple procedure, and shut down with one. Drawing onto the real display can occur immediately, and the virtual screen can be used once initialised. Images are loaded either in .IMG format (see Canvas II for more info) or extracted from compressed libraries created by the image compressor. The memory for the storage of these images can be reserved using one command, and the images given a simple handle in the form of a number. This number is then used to invoke the image for drawing on the real or virtual screen or for use in several drawing effects. Information concerning images loaded can be extracted directly by examining the ImgPos registry, that stores details of all images loaded. Palette routines are dealt with entirely independent of imaging, so the palette can be changed and manipulated at will; palettes have their source in palette files (.PAL) which can be created with Canvas II. Included with the download is a simple graphical demo showing the capabilites of the engine, and full source for the demo and all units, allowing an insight into how to being coding your own MCGA graphics. A short tutorial is included in the download, and the source code for the imaging engine is fully anotated. Much of the MCGA engine is written in pascal, with the exception of the PCX reading routines, screen clearing and virtual page flipping. The engine includes provision for fast pixel read/write, drawing of simple geometical shapes and retrace waiting, as well as fast page flipping and screen clearance. Sadly, time constrains me to this simple list of the engine's attributes, but I hope you can make some sense of the engine and produce the desired results. Any problems, questions of observations, down't hesitate to contact me (preferably through the communicate section). Enjoy it, Jon

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