256-color VGA animation

 Journal:   Dr. Dobb's Journal  Sept 1991 v16 n9 p127(7).
 Title:     256-color VGA animation. (tutorial)
 Author:    Abrash, Michael.
 AttFile:    Program:  GP-SEP91.ASC  Source code listing.

 Summary:   The third in a series of articles on the undocumented
            320-by-240-pixel, 256-color VGA mode (called 'X-mode' by the
            author) develops a routine for copying a nonrectangular image from
            system memory to display memory.  The 'masked copying' routine
            employs a rectangular bitmap that acts as a mask that corresponds
            to the transmitted image.  The bitmap controls which pixels in the
            display are set according to the image and which are left alone.
            Another routine enables masked copies of images in one section of
            display memory to be rapidly copied to another four at pixels at a
            time through selection of appropriate image and mask pairs in
            off-screen display memory.  A compact but powerful animation
            application is developed that utilizes the various capabilities of
            the X-mode.  The program is based on a page-flipping concept, with
            animation movement achieved through transposal of pixels through
            masked copying.
 Topic:     VGA Standard
            Functional Capabilities
            Programming Instruction
 Feature:   illustration
 Caption:   Mode X system memory-to-display memory masked copy routine.
            Generates all four possible mode X image/mask alignments.
            Sample mode X VGA animation program. (program)

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Date this article was posted to GameDev.net: 7/16/1999
(Note that this date does not necessarily correspond to the date the article was written)

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