Q51860: How to Print VGA SCREEN 13 Image to Epson Printer
Article: Q51860
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom appnote BQ0085 SR# S891207-106 | mspl13_basic
Last Modified: 18-OCT-1990
The program listing below demonstrates one method of printing VGA
SCREEN 13 images to an Epson (or compatible) printer with graphics
capability.
This information applies to Microsoft QuickBASIC versions 4.00, 4.00b,
and 4.50 for MS-DOS, to Microsoft BASIC Compiler versions 6.00 and
6.00b for MS-DOS, and to Microsoft BASIC PDS (Professional Development
System) versions 7.00 and 7.10 for MS-DOS. (Earlier versions do not
support VGA SCREEN 13.)
This article is one part of the application note titled "How to Print
BASIC Video Screens to Epson Printers." A printed copy of this
application note can be obtained by calling Microsoft Product Support
Services at (206) 637-7096. This application note can also be obtained
in separate parts in this Knowledge Base by searching for the
following words:
Epson and print and screen and QuickBASIC
If you have a printer other than an Epson-compatible, you must change
the printer control codes used in the following program for setting
line spacing and graphics mode. Control codes can be found in your
printer's manual.
The routine below for printing VGA SCREEN mode 13 is required only if
you aren't running under MS-DOS versions 4.00 or later. In MS-DOS 4.00
and later, the program GRAPHICS.COM supports all standard EGA and VGA
SCREEN modes. Thus, the routine given in a separate article (part of
this application note) for printing CGA SCREEN modes can be used to
print EGA and VGA SCREENs in MS-DOS 4.00 and later.
If you want further information about graphics memory and the various
graphics modes, please refer to the following book, which is available
in bookstores or by calling Microsoft Press at (800) 888-3303 or (206)
882-8661:
"Programmer's Guide to PC and PS/2 Video Systems," by Richard
Wilton (published by Microsoft Press, 1987)
Printing VGA Screen Mode 13
---------------------------
The method used in the program below prints the image sideways, which
avoids the need to do any bit-shifting and uses a simple
eight-dots-per-pixel shading pattern to represent different colors.
To produce different patterns for different colors, each byte of pixel
information must be analyzed. In SCREEN 13, each pixel is represented
by 1 contiguous byte of information, thus allowing 256 colors per
pixel. Since 8 printer pins are fired for each pixel, a direct mapping
of the pixel byte to the printer pins to be fired is done.
As stated before, 8 pins are fired for each pixel; the pins are fired
in a 2 by 4 pattern. Since this is not square, some slight image
distortion does occur.
The Epson printer can fire up to eight pins per graphics byte sent.
Thus, moving from left to right, a loop that reads screen data from
the bottom of the screen upward can access eight vertical columns at a
time. This behavior coincides with the printer firing eight pins at a
time and creates eight horizontal columns on the page, turning the
printout sideways.
DECLARE SUB VGAtoEpson (f$, flip%)
'--- VGAEPSON.BAS
'--- Demonstrates the use of VGAtoEpson, a subprogram that
'--- dumps a SCREEN 13 image to an Epson printer.
'--- Copyright (c) 1988 Microsoft Corp.
REM $INCLUDE: 'QB.BI'
DIM SHARED inregs AS regtype
DIM SHARED outregs AS regtype
SCREEN 13
'--- Draw picture on screen
xmax% = 319
ymax% = 199
halfx% = xmax% / 2
halfy% = ymax% / 2
x% = halfx%
c% = 1
FOR y% = ymax% TO halfy% STEP -2
LINE (halfx%, y%)-(x%, halfy%), c%
LINE (x%, ymax%)-(xmax%, y%), c% + 20
LINE (halfx%, (ymax% - y%))-(x%, halfy%), c% + 40
LINE (x%, 0)-(xmax%, (ymax% - y%)), c% + 60
LINE (halfx% + 1, y%)-((xmax% - x%), halfy%), c% + 80
LINE ((xmax% - x%), ymax%)-(0, y%), c% + 100
LINE (halfx%, (ymax% - y%))-((xmax% - x%), halfy% + 1), c% + 120
LINE ((xmax% - x%), 0)-(0, (ymax% - y%)), c% + 140
x% = x% + (((xmax% + 1) / (ymax% + 1)) * 5)
c% = c% + 1
NEXT y%
CALL VGAtoEpson("LPT1", 1)
SCREEN 0
END
SUB VGAtoEpson (f$, flip%) STATIC
'--- Sends the image on SCREEN 13 to an Epson graphics printer
'--- Parameters:
' f$ - Name of file or device to send image to
' flip% - Invert flag (0 = normal, not 0 = invert)
OPEN f$ FOR BINARY AS 1 'Open the output file
WIDTH #1, 255
esc$ = CHR$(27)
line$ = esc$ + "A" + CHR$(8)
PUT #1, , line$ 'set printer to 8/72 lpi
DEF SEG = &HA000 'Start of VGA screen memory
'--- This loop is the horizontal byte location
FOR Col% = 0 TO 79
'--- Set the printer to receive 800 bytes of graphics data
line$ = esc$ + "L" + MKI$(800)
PUT #1, , line$ '(for init)
'--- This loop is the vertical byte position
FOR row% = 199 TO 0 STEP -1
place& = row% * 320&
place& = place& + Col% * 4
' 4 bytes of pixel information are read in. Each
' of these bytes is broken up across 4 variables
' that are used to fire the printer pins. 2 bits
' from each pixel byte are stored to each of the
' variables.
mem1% = 0 ' Initialize storage bytes for
mem2% = 0 ' color information.
mem3% = 0
mem4% = 0
FOR byte% = 0 TO 3
newplace& = place& + byte%
shift% = 2 ^ ((7 - 2 * byte%) - 1)
mem% = PEEK(newplace&)
mem% = mem% AND 3
mem% = mem% * shift%
mem1% = mem1% OR mem%
mem% = PEEK(newplace&)
mem% = (mem% AND 12) / 4
mem% = mem% * shift%
mem2% = mem2% OR mem%
mem% = PEEK(newplace&)
mem% = (mem% AND 48) / 16
mem% = mem% * shift%
mem3% = mem3% OR mem%
mem% = PEEK(newplace&)
mem% = (mem% AND 192) / 64
mem% = mem% * shift%
mem4% = mem4% OR mem%
NEXT
'--- Flip the byte, if called from
IF flip% <> 0 THEN
mem1% = 255 - mem1%
mem2% = 255 - mem2%
mem3% = 255 - mem3%
mem4% = 255 - mem4%
END IF
'--- Send bytes to device
line$ = CHR$(mem1%) + CHR$(mem2%)
line$ = line$ + CHR$(mem3%) + CHR$(mem4%)
PUT #1, , line$
NEXT
line$ = CHR$(13) + CHR$(10)
PUT #1, , line$
NEXT
ResetPrn$ = esc$ + "@"
PUT #1, , ResetPrn$ ' Reset printer
line$ = CHR$(12)
PUT #1, , line$ ' Send formfeed (page eject)
CLOSE 1 ' All done
END SUB
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