Journal:   Dr. Dobb's Journal  Sept 1991 v16 n9 p127(7).
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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.
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Descriptors..
Topic:     VGA Standard
           Functional Capabilities
           Programming Instruction
           Tutorial
           Animation
           Methods.
Feature:   illustration
           program.
Caption:   Mode X system memory-to-display memory masked copy routine.
           (program)
           Generates all four possible mode X image/mask alignments.
           (program)
           Sample mode X VGA animation program. (program)

