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QB4UTIL.BI
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1993-10-19
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'
' QUICKBASIC SUPPORT ROUTINES FOR THEDRAW OBJECT FILES
'-----------------------------------------------------------------------------
' Compatible with Microsoft QuickBasic v4.0 and v4.5 text modes.
'-----------------------------------------------------------------------------
'
' There are a few routines within the QB4UTIL.LIB file. These are
' (along with brief descriptions):
'
' UNCRUNCH - Flash display routine for crunched image files.
' ASCIIDISPLAY - Display routine for ascii only image files.
' NORMALDISPLAY - Display routine for normal full binary image files.
' INITSCREENARRAY - Maps a dynamic integer array to the physical video
' memory.
'
'=============================================================================
' UNCRUNCH (imagedata,video offset)
' ASCIIDISPLAY (imagedata,video offset)
' NORMALDISPLAY (imagedata,video offset)
'=============================================================================
'
' These three subroutines operate similarly. Each takes a specific data
' format (TheDraw crunched data, ascii only, or normal binary) and displays
' the image on the screen. Monochrome and color text video displays are
' supported. The integer offset parameter is useful with block images,
' giving control over where the block appears.
'
' Example calls:
' CALL UNCRUNCH (ImageData&,vidoffset%) <- for crunched data
' CALL ASCIIDISPLAY (ImageData&,vidoffset%) <- for ascii-only data
' CALL NORMALDISPLAY (ImageData&,vidoffset%) <- for normal binary data
'
' The parameter IMAGEDATA is the identifier you assign when saving
' a QuickBasic object file with TheDraw. ImageData actually becomes a
' short function returning information Uncrunch, AsciiDisplay, and
' NormalDisplay use to find the screen contents. In addition, three
' other related integer functions are created. Assuming the identifier
' IMAGEDATA, these are:
'
' IMAGEDATAWIDTH%
' IMAGEDATADEPTH%
' IMAGEDATALENGTH%
'
' The width and depth functions return the size of the block in final
' form (ie: a full screen would yield the numbers 80 and 25 respectfully).
' The length function returns the size of the stored data. For crunched
' files and block saves this might be very small. For a 80x25 full screen
' binary image it will be 4000 bytes. The integer functions are useful for
' computing screen or window dimensions, etc...
'
' You must declare all four functions in your Basic source code before
' they can be used (naturally). The following code example illustrates.
' The identifier used is IMAGEDATA. The data is a 40 character by 10 line
' block saved as normal binary.
'
' ----------------------------------------------------------------------
' REM $INCLUDE: 'QB4UTIL.BI'
' DECLARE FUNCTION ImageData& ' Important! Do not neglect
' DECLARE FUNCTION ImageDataWidth% ' the "&" and "%" symbols
' DECLARE FUNCTION ImageDataDepth% ' after the function names.
' DECLARE FUNCTION ImageDataLength%
'
' CALL NORMALDISPLAY (ImageData&, 34 *2+( 5 *160)-162)
' ----------------------------------------------------------------------
'
' That's it! The above displays the 40x10 block at screen coordinates
' column 34, line 5 (note these two numbers in above example). If the
' data was crunched or ascii use the corresponding routine.
'
' Note: The ascii-only screen image does not have any color controls.
' Whatever the on-screen colors were before, they will be after.
' You might want to insert COLOR and CLS statements before calling
' the ASCIIDISPLAY routine.
'
' Regardless of which routine used, each remembers the original horizontal
' starting column when it goes to the next line. This permits a block to
' be displayed correctly anywhere on the screen. ie:
'
' +-------------------------------------------------+
' | |
' | | <- Pretend this
' | | is the video
' | ┌─────────────────────┐ | display.
' | │█████████████████████│ |
' | │█████████████████████│ |
' | │██ ImageData block ██│ |
' | │█████████████████████│ |
' | │█████████████████████│ |
' | │█████████████████████│ |
' | └─────────────────────┘ |
' | |
' | |
' | |
' +-------------------------------------------------+
'
'
' The ImageData block could be shown in the upper-left corner of the
' screen by changing the call to:
'
' CALL NORMALDISPLAY (ImageData&,0)
'
' Notice the video offset has been removed, since we want the upper-left
' corner. To display the block in the lower-right corner you would use:
'
' CALL NORMALDISPLAY (ImageData&, 40 *2+( 15 *160)-162)
'
' The block is 40 characters wide by 10 lines deep. Therefore to display
' such a large block, we must display the block at column 40, line 15.
' (column 80 minus 40, line 25 minus 10).
'
'
' NOTES ON THE UNCRUNCH ROUTINE
' --------------------------------------------------------------------------
'
' Many people favor "crunching" screens with TheDraw because the size
' of the data generally goes down. When uncrunching an image however,
' there is no guarantee what was previously on-screen will be replaced.
'
' In particular, the uncruncher assumes the screen is previously erased to
' black thus permitting better data compression. For instance, assume the
' video completely filled with blocks, overwritten by an uncrunched image:
'
' ┌─────────────────────┐ ┌─────────────────────┐
' │█████████████████████│ │tetetetetet██████████│
' │█████████████████████│ │█████████████████████│
' │█████████████████████│ │ etetetetetete████│
' │█████████████████████│ │tetetetet████████████│
' │█████████████████████│ │ ete█████████│
' │█████████████████████│ │ etetetetetet██│
' └─────────────────────┘ └─────────────────────┘
' before uncrunch after uncrunch
'
' By omitting a CLS statement, the new text appears surrounded by bits of
' the previous screen. Proper usage would typically be:
'
' ----------------------------------------------------------------------
' REM $INCLUDE: 'QB4UTIL.BI'
' DECLARE FUNCTION ImageData& ' Important! Do not neglect
' DECLARE FUNCTION ImageDataWidth% ' the "&" and "%" symbols
' DECLARE FUNCTION ImageDataDepth% ' after the function names.
' DECLARE FUNCTION ImageDataLength%
'
' COLOR 15,0 : CLS ' Clear to black screen
' CALL UNCRUNCH (ImageData&, 34 *2+( 5 *160)-162)
' ----------------------------------------------------------------------
'
'
'=============================================================================
' INITSCREENARRAY
'=============================================================================
'
' To directly access the video screen memory requires you to use the
' PEEK/POKE statements after setting the DEF SEG value. A cumbersome
' and compiler inefficient approach. In addition, you must have some
' way of determining if a monochrome or color video is being used before
' the DEF SEG can be set properly.
'
' This subroutine offers a simpler approach, by effectively mapping or
' placing an integer array over the video screen. Instead of PEEK/POKE,
' you merely reference an array element. ie:
'
' ----------------------------------------------------------------------
' REM $INCLUDE: 'QB4UTIL.BI'
'
' REM $DYNAMIC <- very important to place this before DIM statement
' DIM S%(0)
' CALL INITSCREENARRAY (S%())
'
' S%(0) = ASC("H") + 15 *256 + 1 *4096
' S%(1) = ASC("E") + 15 *256 + 1 *4096
' S%(2) = ASC("L") + 15 *256 + 1 *4096
' S%(3) = ASC("L") + 15 *256 + 1 *4096
' S%(4) = ASC("O") + 15 *256 + 1 *4096
' ----------------------------------------------------------------------
'
' The above example directly places the message "HELLO" on the screen
' for you, in white lettering (the 15*256) on a blue background (1*4096).
' To alter the foreground color, change the 15's to some other number.
' Change the 1's for the background color.
'
' Each array element contains both the character to display plus the
' color information. This explains the bit of math following each
' ASC statement. You could minimize this using a FOR/NEXT loop.
'
' The S% array has 2000 elements (0 to 1999) representing the entire
' 80 by 25 line video. If in an EGA/VGA screen mode change the 1999 to
' 3439 or 3999 respectfully.
'
' There is no pressing reason to use the array approach, however it
' does free up the DEFSEG/PEEK/POKE combination for other uses. In
' any case, enjoy!
'
'
DECLARE SUB UNCRUNCH (X&, Z%)
DECLARE SUB ASCIIDISPLAY (X&, Z%)
DECLARE SUB NORMALDISPLAY (X&, Z%)
DECLARE SUB INITSCREENARRAY (A%())