Cream of the Crop 1/Cream of the Crop 1.iso/PRINTER/LJVGA161.ARJ/LJVGA.TXT

Text File | 1992-08-18 | 28KB | 713 lines

LJVGA:  A VGA to HP Laserjet Print Screen Utility

Version 1.61

Copyright (c) 1992 Ares Technologies.  All Rights Reserved.


































VGA is a trademark of International Business Machines
Corporation.
Hewlett-Packard and HP are registered trademarks of Hewlett-
Packard Corporation.


LJVGA:  A VGA to HP Laserjet Print Screen Utility


LJVGA is Terminate-and-Stay-Resident (TSR) program that allows
you to print any VGA or Super VGA screen to an HP Laserjet or
compatible printer.  With a memory overhead of only 8.5k, you can
print anything you can display on your VGA card - graphics, text,
even hi-res text and 256-color screens!

LJVGA is simple to use.  Just run the command LJVGA, and you're
ready to print anything!  Hitting the Print Screen key (PrtSc)
will activate LJVGA, causing it to print your current screen to
the printer.  Text screens print just like they look, with lines
and other special characters you don't usually get.  Graphics
screens are automatically scaled to the resolution and page you
choose.


NEW AND IMPROVED!


If you have previously used LJVGA, you will find a number of
useful enhancements in this version.  Perhaps the most popular of
these is the new orientation option, which now allows you to
print your graphics screens in landscape mode!  Also new are a
selection of dither algorithms and contrast and brightness
controls.  With these new controls you have much more control
over the appearance of your printed output.

The dither algorithms in this version have changed somewhat.
Previous versions of LJVGA used one dither - the Floyd-Steinberg
algorithm.  Version 1.61 adds new variations of the Bayer
algorithm.  These two dithers are 30% faster than the Floyd-
Steinberg algorithm, but produce a poorer image.  The older Floyd-
Steinberg method is still available, but is no longer the
default.  If you notice a difference in your output with this
version, it is because you are now using the Bayer algorithms.
See the section on Using LJVGA for instructions on choosing the
selecting the appropriate algorithm.


USING LJVGA


Using LJVGA is simple.  Running the command LJVGA will load LJVGA
as a TSR.  LJVGA will load with its default options, allowing you
to print most any text or graphics screen by simply hitting the
Print Screen key.  You can modify the default options by using a
combination of command-line switches, either the first time you
run LJVGA, or later to modify the options already loaded in
memory.  LJVGA cannot be loaded twice.  If you have already
loaded LJVGA, it will update the copy in memory when you run it
again.

LJVGA supports several different command-line switches.  These
can be entered alone or as a group to change the default behavior
of LJVGA.  Be aware that when you use LJVGA to update a TSR
already in memory, all options are reset to their defaults.
Therefore, you must be careful to use all appropriate options
each time you run LJVGA.

LJVGA can also read its options from the DOS environment.  When
it is run, LJVGA will look for the environment variable "LJVGA".
If "LJVGA" is set, LJVGA will read the value as if it were
entered on the command-line.  The environment is read first, so
settings entered on the command-line will override any settings
entered in the environment.  See the examples below for more
information.


The possible options are listed below.

-?      Print synopsis.  This option prints a copyright notice
        and a short summary of options.  No other action is taken
        if you use this option.

-d      Disable LJVGA.  This option will cause LJVGA to return
        control to the previously loaded print-screen routines
        (usually in the system BIOS).  This option does not
        remove LJVGA from memory.

-e      Enable LJVGA.  This option will enable LJVGA if it has
        been previously disabled.  LJVGA will regain control with
        the settings it had when it was disabled.

-u      Unload LJVGA.  This option will disable LJVGA and remove
        it from memory.  LJVGA will only unload if it is the last
        TSR loaded.

-n      Instant print.  This option will cause LJVGA to
        immediately print the current screen without becoming
        resident.  This option can be used to run LJVGA from
        batch files, and could be used to create a primitive file
        printing program.  This option will cause LJVGA to ignore
        any previously loaded copy, and will use only default
        options and options set on the command-line.

-lN     Set printer port.  This option allows you to change the
        printer port LJVGA will print to.  Possible values for N
        are 1 for LPT1, 2 for LPT2, or 3 for LPT3.  You can also
        set N to 0 to print to PRN:.  Note: Setting the printer
        port to 0 will also force LJVGA into DOS print mode
        (explained below).

-pN     Set print mode.  This option allows you to change the
        method by which LJVGA sends data to the printer.  This is
        useful in cases where you are using certain print
        redirectors or when you have a defective BIOS.  Possible
        values for N are listed below.

        0 - BIOS print mode.  All printing is done through calls
            to the system BIOS.  This is the default option and
            is the fastest print mode.  This option should be
            chosen except in special situations.

        1 - BIOS print mode with DOS Signalling.  This print mode
            is intended for use with some network software.  When
            using this mode, LJVGA prints all data through the
            system BIOS, but also uses DOS to open and close a
            phantom print file.  This method can be used on
            certain networks to signal the beginning and ending
            of a print job.

        2 - DOS print mode.  When using this print mode, LJVGA
            prints all data through DOS calls.  This option is
            included for situations in which compatibility is a
            problem, or where output should be redirected to
            special DOS devices.

-rN     Set resolution.  This option allows you to set your
        printer's graphics resolution in dots-per-inch (DPI).
        Possible values for N are 75, 100, 150, and 300.  The
        default is 300 DPI.  LJVGA will automatically scale
        graphics to the resolution you choose.

-ox     Set page orientation.  This option allows you to select
        portrait (upright) or landscape (sideways) graphics.  Set
        x to "p" for portrait or "l" for landscape.  The default
        is portrait graphics.

-f      Suppress form-feed.  Normally, LJVGA will eject the page
        from the printer once it has finished the screen.  This
        option will cause LJVGA to leave the page in the printer
        until it is full.

        NOTE:  You may run out of memory while printing high-res
        graphics with this switch.  Make sure your printer has
        enough memory for the whole page!

        Also, LJVGA normally resets the printer options to
        produce the cleanest print possible.  It cannot do this
        while using the -f option.  If you experience problems
        printing with the -f option, manually reset your printer
        before printing.

-i      Invert colors.  This option will invert the colors for
        graphics screens so that white on the screen will print
        as black and vice-versa.  Other colors are similarly
        reversed, printing a "negative" of the screen image.

-aN     Select dither algorithm.  This option allows you to
        select the method LJVGA uses for creating the output
        image.  The "dither" is the method by which LJVGA
        determines the pattern of dots to print on the output to
        simulate different colors.  The different algorithms
        produce different results and are useful for different
        types of applications.  Experiment with these options to
        see which works best for you.  Possible values for N are
        listed below.

        0 - Bayer-Dispersed algorithm.  This is the fastest
            dither method and is the default.  This is a good
            general-purpose algorithm and is characterized by
            cross-hatch patterns in the output.

        1 - Bayer-Clustered algorithm.  This is a modification of
            the Bayer-Dispersed algorithm and is commonly
            referred to as "halftoning."  This method produces a
            pattern of different size dots producing an image
            similar to the pictures in a newspaper.

        2 - Bayer Semi-Clustered.  This is a variation of the
            Bayer-Clustered algorithm that produces four smaller
            dot rather than one large dot.  Results are
            comparable to the Bayer-Clustered algorithm, but the
            resulting image is more pleasing due to the smaller
            dot size.

        3 - Bayer Semi-Clustered Vertical algorithm.  This is a
            modification of the Bayer algorithms which produces
            vertical line patterns in the image.  This produces a
            very pleasing, consistent image, but results in very
            poor contrast.

        4 - Floyd-Steinberg algorithm.  This dither method is
            slower than the Bayer algorithms, but produces much
            better output for continuous-tone images.  This is
            the same algorithm used in the original versions of
            LJVGA.

-cN     Set contrast.  This option allows you to change the
        contrast of the printed output.  Areas of similar color
        can be blended or accentuated using this option.
        Possible values for N range from -32 to 1024.  Negative
        values decrease the contrast, with -32 corresponding to
        50% grey output.  Positive values increase the contrast,
        with 1024 corresponding to an image with only pure black
        and white.  0 is the default and results in no
        adjustment.

-bN     Set brightness.  This option allows you to change the
        brightness of the printed output.  The output can be made
        "blacker" or "whiter" with this option.  Possible values
        for N range from -64 to 64.  Negative values increase the
        black level, with -64 corresponding to a completely black
        image.  Positive values increase the white level, with 64
        corresponding to a completely white image.  0 is the
        default and results in no adjustment.

        Note:  At 300 DPI on most laser printers, the black dots
        tend to overwhelm the white space, resulting in fairly
        dark images.  This can be compensated by increasing the
        brightness.  Good results have been achieved print GIF
        images with a brightness of approximately 16.

-sN,N   Set scaling.  This option allows you to control the size
        of the printed image.  LJVGA will normally print the
        largest image that will fit on the page at the given
        orientation and resolution, but you can scale the size up
        or down with this option.

        This option takes a pair of numbers representing the x-
        and y-scaling respectively.  Each number represents the
        number of printed pixels that will be used to represent
        each screen pixel in the respective direction.  For
        example, LJVGA normally uses the values 3,3 when printing
        a 640x480 screen at 300 DPI in portrait orientation.
        This means that for each pixel on the screen, LJVGA will
        print a box 3 pixels wide by 3 pixels long.

        These values come from the following computation.  Most
        laser printers can print approximately 2450 pixels across
        at 300 DPI.  We want to represent 640 screen pixels
        across, so 2450 / 640 = 3.83.  Since LJVGA cannot print
        fractional pixels, it will print 3 pixels across for
        every screen pixel.  This is the x value.  The y value is
        computed from the x value to produce the correct aspect
        ratio on output.

        With this option, you can set the scaling for a smaller
        image or for a larger image.  If you specify a scaling
        factor greater than the maximum, the output image will be
        clipped to the dimensions of the page.

        You do not have to set both values.  If either number
        given is 0, the scaling value for that direction will be
        determined from the value for the other direction in
        order to preserve the correct aspect ratio.  Setting both
        values to 0 will result in the default, maximum-size
        image.

        For your reference in determining the appropriate scaling
        values, LJVGA assumes that the output must fit on a 8.25"
        x 10" page.  The number of output pixels that this
        represents varies depending on the resolution chosen.
        Also, note that the x and y values correspond to screen
        dimensions, and thus may change depending on the page
        orientation selected.

-z      Load debugging code.  This option will cause LJVGA to
        load an additional 1k of debugging code.  This option can
        only be specified the first time LJVGA is loaded and
        cannot be disabled without unloading LJVGA.  Once this
        option is loaded, LJVGA will produce an extra page
        containing information about the state of your VGA card
        each time you press the Print Screen key.  This option
        should be used on the advice of Ares Technologies
        personnel to assist in resolving printing problems.

-xN     Set VGA card type.  This option allows owners of ATI VGA
        boards to use LJVGA.  Because the ATI BIOS does not
        return certain parameters correctly, this option is
        necessary to print the ATI high-resolution modes.  Owners
        of all other board types should use the default BIOS
        option.  Possible values for N are listed below.

        0 - BIOS support.  This is the default for LJVGA.

        1 - ATI hardware support.  This option allows LJVGA to
            access the ATI hardware directly.


EXAMPLES


LJVGA             : Load LJVGA into resident memory using the
                    default options.

LJVGA -l2         : Load LJVGA into resident memory and redirect
                    output to LPT2:.

LJVGA -ol -a4     : Load LJVGA into resident memory and choose
                    landscape graphics with Floyd-Steinberg
                    dithering.

LJVGA -r75 -n     : Print the current screen at 75 DPI.  Do not
                    load LJVGA into resident memory.

LJVGA -s1,1       : Load LJVGA into resident memory and set the
                    scaling so that each screen pixel is
                    represented by one printer pixel.

LJVGA -s0,4       : Load LJVGA into resident memory and set the
                    scaling so that each screen pixel is
                    represented by 4 printer pixels down and by
                    an appropriate number of printer pixels
                    across.

LJVGA -d          : Disable a previously loaded copy of LJVGA and
                    return print-screen control to the system
                    BIOS.

set LJVGA=-b16 -ol
LJVGA             : Load LJVGA into resident memory and choose
                    landscape graphics with brightness set to 16.

set LJVGA=-ol -a4
LJVGA -a0         : Load LJVGA into resident memory and choose
                    landscape graphics.  Choose Bayer-Dispersed
                    dithering.  (The command line option -a0
                    overrides the environment option -a4.)


HOW IT WORKS


LJVGA has two primary jobs - printing text and printing graphics.
Printing text is straightforward.  LJVGA simply reads the text
from the screen and sends it to the printer.  LJVGA has an
advantage over the built-in print screen routines, however, since
it knows how to control the laser printer.  Thus, LJVGA can set
up the printer to print the extended characters such as the line-
drawing characters.  It can also set up the printer to handle
special screen modes such as the 132x60 text modes available on
some SuperVGA cards.

Printing graphics is where LJVGA is most useful.  DOS has only
very basic graphics printing capability - and even then this
ability is only made available by loading large TSRs.  LJVGA
solves this shortcoming by providing high-quality printing in a
very small package - approximately 8.5k resident.

The biggest problem faced by LJVGA is how to produce a
recognizable image of the screen, which can have up to 256 colors
out of a palette of 262,144 colors, on the laser printer, which
has only 2 colors - black and white.  LJVGA solves this problem
by a method called dithering.  This is a method by which a larger
number of colors can be represented by using patterns of dots
chosen from a smaller number of colors.  In this case, that
allows up to 256 colors to be represented by different patterns
of only two colors.

Actually, colors images cannot be accurately reproduced on a
black-and-white printer (obviously!)  Therefore, LJVGA actually
produces a print that is based on the intensities of the colors
on the screen.  This is the same as saying that if you were to
convert the colors on screen to shades of grey, LJVGA produces an
approximation of the shades-of-grey screen.  This works because
the human eye is more sensitive to certain colors than to others,
thus these colors can be approximated by different shades of
grey.  Thus, by printing areas of dots of varying densities,
LJVGA can approximate these grey shades.  Printing just a few
dots results in bright areas, while printing more dots results in
dark areas.

LJVGA uses two major varieties of dithering to produce these dot-
densities.  The first, fastest method is known as ordered or
Bayer dithering and uses a predefined pattern to reproduce each
color.  This pattern contains a set of numbers representing color
threshold values.  As the image is generated, each screen pixel
is compared against the threshold value at the spot in the
pattern where that pixel will be plotted.  If the pixel color is
greater than the threshold value, a dot is printed.  Otherwise,
no dot is printed.  Thus the output image has a regular, ordered
appearance, because it is based completely on the original
pattern.

LJVGA uses two different patterns for this method.  The first is
a "dispersed" pattern which produces dots in a widely spread
pattern.  Because of the way this pattern is generated, it
produces a characteristic cross-hatched output.  The second
pattern is a "clustered" pattern.  In this pattern, similar
threshold values are grouped closely together to produce large
dots.  This pattern generates an image which appears to be made
up of different sized dots, much like the pictures in a
newspaper.

The second variety of dithering is known as random dithering
because it produces dots in a seemingly random manner.  This
dither is also known as an error-dispersion dither because of the
way it produces dots.  This method works in two steps.  In the
first step, the current screen pixel is compared against a
predefined threshold value.  If the color is greater than the
threshold, a dot is printed, otherwise, no dot is printed.  The
second step compares what is actually printed against what should
be printed.  This produces an "error" value which is divided up
and added to the neighboring screen pixels.  This is repeated for
every pixel in the image.  Thus if a dot is supposed to be dark
grey and we plot black, the error value generated reduces the
chance that the next pixel plotted will also be black, ensuring
that we get an area of "dark grey" on the output.

This method is slower than the ordered dithers because of the
math involved, but because it is based on the image itself, and
not on a predefined pattern, it significantly reduces the chances
of incidental patterns ("artifacts") emerging in the final
output.  There are many variations of random dithering, but LJVGA
uses only one of these, the Floyd-Steinberg dither.


ADDITIONAL NOTES


Printing graphics on a laser printer requires large amounts of
memory.  If you are planning on printing graphics screens at 300
DPI, you should have at least 1 megabyte of memory in your laser
printer.  512k should be sufficient for printing text and
graphics at lower resolutions.

LJVGA is only guaranteed to work with VGA screen modes that are
supported by video BIOS.  Most SuperVGA cards have extended BIOS
chips which support all of the vendor-defined modes and thus will
work with LJVGA.  However, some graphics packages such as PICEM
and VPIC can directly program VGA cards into modes not supported
by BIOS.  LJVGA is NOT guaranteed to work with these modes.

For the future, we plan to enhance LJVGA to support VGA hardware
directly.  This will increase its speed and flexibility, and will
allow it to print these special modes.  If you discover any
unsupported modes, please let us know about them and we will
consider them when the enhancements are made.


REPORTING BUGS


If you discover what seems to be a bug in LJVGA, please let us
know!  If we verify a bug you discover, you will receive a free
registered version of the fixed program!




CURRENT KNOWN PROBLEMS


Only supports video BIOS-supported modes.

When using print modes 1 or 2, LJVGA cannot be invoked while a
DOS function is active.  This is due to an untraceable bug and
will be corrected soon.


LJVGA RELEASE HISTORY


v0.50  (910307)

Initial release.

v1.00  (910326)

Added resolution option.
Added printer port option.
Added error detection for missing or off-line printers.
Added the ability to detect and update a previously loaded copy.

v1.10  (910622)

Added the disable/enable options.

v1.20  (910730)

Added suppress form-feed option.

v1.30  (920304)

Fixed a bug with command-line parsing under MS-DOS 4.0/5.0.
Added invert option.
Added unload option.

v1.50  (920422)

Added instant print option.
Added print mode option.
Added page orientation option.
Added Bayer dithers.  Up to 30% faster than previous dither.
Added contrast option.
Added brightness option.
Added scaling option.
Added debugging option.
Fixed an error in the Floyd-Steinberg dithering option.  Output
     is now much improved.
Added better interrupt handling for improved safety and error
     control.
Fixed a bug which would allow LJVGA to load when using the
     enable/disable controls.
Fixed a bug which prevented LJVGA from finding a previously
     loaded copy in fragmented memory.
Fixed text print routine so that control characters are printed,
     not interpreted.

v1.52  (920608)

Corrected color mapping for 16-color modes.
Corrected control character printing.  This bug was only
     noticable on non-HP printers.

v1.53  (920627)

Added use of DOS print-screen busy flag.
Made resident section more crash-proof.
Added serial numbering.

v1.61  (920814)

Added two new Bayer dithers.
Modified to keep only one dither pattern in active memory.
Increased support for older networks.
Fixed a problem with the DOS print-logging flag in Gateway
     machines.
Added color resolution checks for certain VGA adapters.
Added ATI-specific code.


TECHNICAL SUPPORT


If you have any questions or comments about LJVGA, contact:

    Mail:       Ares Technologies
                243 Fairfax Rd.
                Blacksburg, VA  24060

    Phone:      [phone]

    E-Mail:     CIS 73237,1572


Ares Technologies is also available for custom programming
projects.  Please feel free to contact us if you would like to
discuss your programming needs.




REGISTRATION


If you find LJVGA useful and convenient, a registration of $10 or
more would be appreciated.

If you send $20 or more, you will receive a disk containing the
current version of the software.  You will also receive a disk
with the next major version when it becomes available.

For a fee of $50, you will receive a lifetime registration for
LJVGA.  This will entitle you to every major and minor version of
LJVGA as they are released.  These will be automatically sent to
you free of additional charge.

Site licenses are available for commercial and multiple user
organizations.  Please read the file REGISTER.TXT for more
information.

Reseller information is available for developers wishing to
bundle pre-registered versions of LJVGA with their own software.
Please contact Ares Technologies directly for more information.

Please state the current version of the software you are using.
Send check or money order to:

                        Ares Technologies
                         243 Fairfax Rd.
                      Blacksburg, VA  24060


You can also order LJVGA from the Public Software Library with
your Visa, MasterCard, American Express, or Discover card at one
of the following numbers.  These numbers are for ordering only.
For all other information concerning LJVGA, please contact Ares
Technologies directly.

    Mail:       PsL
                P.O. Box 35705
                Houston, TX  77235-5705

    Phone:      [phone]-PSL
                713-524-6394

    FAX:        [phone]

    E-Mail:     CIS 71355,470
SOFTWARE LICENSE


LJVGA VGA/HP Laserjet Print Screen Utility
Copyright (c) 1992 Ares Technologies.  All Rights Reserved.


Notice:  By using LJVGA, you agree to be bound by the terms of
this license.  If you do not agree with the conditions listed
herein, you may not use LJVGA.  If you have any questions
regarding your software license, please contact Ares Technologies
at the address listed elsewhere in this document.


You may use, copy, and distribute LJVGA for noncommercial
purposes only, provided the following conditions are met:

    No fees may be charged for use or distribution.

    The program and accompanying documentation must be
distributed in unmodified form.

    Reverse compilation, reverse engineering, or any other form
of code decomposition is expressly prohibited.

    Clubs, user groups, and shareware distributors may charge a
nominal fee for expenses and handling only while distributing
LJVGA.  Operators of electronic bulletin board systems may charge
only normal membership fees, and may not require additional fees
for access to LJVGA.  Distributors are encouraged to register
with Ares Technologies.  See the file SYSOP.TXT for additional
information.

    Site and commercial licenses are available for LJVGA.  Please
read the file REGISTER.TXT, or contact Ares Technologies for more
information.




Ares Technologies hereby disclaims all warranties relating to
this software, express or implied, including without limitation
any warranties of merchantability or fitness for a particular
application.  Ares Technologies will not be liable for any
damages, direct, consequential, or otherwise, suffered due to
loss of data or any other reason, even if Ares Technologies has
been advised of the possibly of such damage.  In no event shall
Ares Technologies' liability for any such damages exceed the
price paid for the license to use the software, regardless of the
form of the claim.  The user of this software bears all risk as
to the quality and performance of the software.