OS/2 Shareware BBS: 11 Util/11-Util.zip/VGAUTILS.ZOO/vgautils.doc

Text File | 1989-07-09 | 13KB | 269 lines

VGAUTILS.DOC FILE FOR VGA MONITOR SETUP/TEST UTILITIES:
VGRID.EXE, VGRID-M.EXE, VBOX.EXE, VGACOLOR.EXE

Contained in this "package" (the file VGAUTILS.ARC) are four
utilities that you can use to test and align your VGA display
adapter/monitor combination, along with this file, VGAUTILS.DOC.
VGRID.EXE, VGRID-M.EXE, and VBOX.EXE require a VGA or 100%
compatible display adapter and a VGA or VGA-compatible
multiscanning monitor.  They may work with certain "Super EGA"
cards with 640 x 480 16 color modes that are compatible with VGA
mode 18 (decimal) when used with a monitor capable of displaying
this resolution.  Beyond this, I cannot make any claims for the
compatibility of these programs with your equipment.

VGACOLOR.EXE requires a VGA or MCGA (or 100% compatible) display
adapter, and a VGA or compatible monitor.

These programs were written and compiled in Microsoft QuickBASIC
version 4.5.  They are to be considered as FREE software for
everyone's use and enjoyment.  The descriptions of the programs
are as follows:


VGRID.EXE

This program puts a white grid on your monitor screen in VGA mode
18 (decimal), -the 640 x 480 16 color graphics mode.  The outer
border of the grid is 640 pixels wide by 480 pixels high.  The
individual boxes of the grid are 40 pixels on a side.  This
screen pattern is useful for testing and aligning you VGA or
multiscanning monitor for the following:

     FOCUS - The grid should, of course, be sharp all the way
     across your monitor screen.  If it is not, the focus may
     need to be adjusted.  Some poorly designed monitors may have
     trouble maintaining focus in the corners when the center of
     the screen is sharp.

     VERTICAL AND HORIZONTAL SIZE - The accurate display of
     graphics is important when using CAD or paint programs, -the
     size and shape of displayed objects must be correct.  This
     requires that the vertical and horizontal size controls of
     your monitor be correctly set.  Since the borders of the
     VGRID screen display measure the full 640 by 480 pixels
     (width to height) of the VGA mode 18 screen, they should be
     displayed at an aspect ratio of 4 units wide to 3 units high
     (or 1.33 to 1, if you're so inclined).  If this is not the
     case, adjust your monitor's vertical size control and/or the
     horizontal size control for the correct screen aspect ratio.
     You can set this by actually measuring the size of the grid
     on the screen, or you can simply set your monitor so that
     the individual boxes that make up the grid appear to be
     square.  You can also set your monitor's screen height and
     width visually using the program VBOX.EXE.

     CENTERING - If your monitor's horizontal and vertical
     position controls are set correctly, the grid display should
     be centered on the screen.  Adjust these controls accord-
     ingly if this is not the case.

     HORIZONTAL AND VERTICAL LINEARITY - The boxes that make up
     the grid display should (ideally) appear as perfect squares
     of the same size across the entire screen display.  If they
     are not all the same size, the horizontal and vertical
     linearity adjustments of your monitor may be incorrectly
     set.  Please note that it may be impossible to achieve
     perfect linearity across the screen, -sometimes a compromise
     setting may have to be determined to achieve the best
     overall display quality.

     CURVILINEAR DISTORTION - The horizontal and vertical lines
     in the grid should appear perfectly straight.   They may,
     however, be curved outward (barrel distortion) or inward
     (pincushion distortion) in monitors that are out of adjust-
     ment or just plain poorly designed.  Some monitors have
     provisions to correct for these problems, others may not.

     CONVERGENCE - In a color monitor, the three electron beams
     for each of the primary colors (red, green, and blue) must
     be aligned so that they meet ("converge") to form the
     smallest possible point on the screen.  If convergence is
     improperly set, there is a loss of sharpness in the form of
     colored fringes on text and graphics.  The white grid
     display of VGRID.EXE, when used in conjunction with the
     magenta grid produced by VGRID-M.EXE, can be used to check
     and set your monitor's convergence.


The VGRID display will remain on your screen until you press a
key.


VGRID-M.EXE

VGRID-M.EXE can be used along with VGRID.EXE to check and align
convergence in color monitors.  VGRID-M produces a display
identical to that of VGRID, except that the grid is magenta
instead of white.

The NEC Multisync II service manual recommends using magenta and
white "crosshatch" displays (such as those produced by VGRID-M
and VGRID) to set convergence.  The magenta grid display is used
first to set the alignment of blue and red.  There are tabs along
the neck of the monitor's CRT tube that move small permanent
magnets which control the convergence of these beams in both the
horizontal and vertical directions.  The idea is to get the
horizontal and vertical magenta lines to appear as sharp as
possible, without red or blue fringes.

Next, a white grid display (VGRID.EXE) is used to set the
convergence of magenta (red + blue) with green.  A different set
of tabs along the neck of the CRT are used this time, but the
principle is the same as that used in the red/blue alignment.
The white grid lines should appear as sharp as possible, with no
colored fringes.  When this condition has been obtained, all
three colors are properly converged.

The procedure for the convergence alignment of monitors other
than the NEC Multisync II should be similar.  It is recommended
that you obtain the service manual for your particular brand and
model of monitor, and adhere to its recommendations for setting
convergence and any other monitor adjustments.  Care must be
taken, as there may be control tabs near those used for con-
vergence that are used to set other things (such as color purity)
that you DON'T normally want to disturb.

CAUTION: Aligning convergence and other monitor settings usually
requires that you remove the cover from your monitor, thus
exposing yourself to the dangerous voltages that are inside.
Care must be taken to avoid electrical shock!  Nonconducting
plastic alignment tools (available at places like Radio Shack)
should be used.  Again, the best advice is to obtain the service
manual for your monitor, and follow its recommendations.

It may be impossible to obtain perfect convergence across the
full width of your monitor's screen.  Typically, convergence
error is greater in the corners.  As is the case with linearity,
a compromise setting may be necessary to obtain the best overall
alignment across the entire display width.


VBOX.EXE

This is a program that generates a screen display especially made
for setting the vertical and horizontal size controls of your
monitor.  The circles should appear to be perfectly round, and
the boxes should be perfectly square.  The border of the display
measures 640 pixels wide by 480 pixels high, so the screen aspect
ratio should be 4 to 3 (or 1.33 to 1).


VGACOLOR.EXE

This is a demo program that shows the capabilities of the
320 x 200 256 color mode (decimal mode 19) of the VGA or MCGA
display adapters.  The 256 colors used can be chosen from a total
"palette" of "256K" (actually 262,144) possible colors, which
vary in hue (shade), intensity (brightness), and saturation.
The colors of the palette are produced from all the possible
combinations of the three primary colors (red, green, and blue),
each of which can be varied through 64 steps of intensity (64 x
64 x 64 = 262,144).  On monochrome monitors, these colors are
displayed as 64 shades of gray.

The first screen shows the "default" color settings of the 256
screen color attributes.  The numbers and letters along the top
and left side of the color bar display are hexadecimal numbers.
You can determine the hex attribute number of a displayed color
bar by using the numeral displayed to the left of its horizontal
display row as the first digit, and the numeral directly above
its vertical display column as the second digit.

The top row (attributes 00H to 0FH) of the first screen is the same
as the "default" color set used by the EGA.  The second row (10H
to 1FH) shows the range of 64 gray levels possible in 16 evenly
spaced steps.  Attributes 20H through F7H consist of 24 color
groups, each consisting of nine shades of a color.  Three
intensity levels and nine saturation levels are provided for each
shade.  Attributes F8H through FFH are set to black for reasons
known only to the designers of the VGA standard.

The second screen uses attributes 20H through FFH to show how the
colors used can be varied in hue (shade) and intensity (bright-
ness).  Hue is varied along the vertical axis of the display.
The primary colors (red, green, blue), secondary colors (yellow,
magenta, cyan), and some intermediate shades are shown.   The
"spacing" of the hues shown is not "even" in the sense of the
numerical values of each color, but were chosen to visually
present discrete "steps" of hue variation.  Exactly how
this looks to you will depend on the contrast and brightness
settings of your monitor, as well as your own eyes.  The 64 step
range of intensity/brightness for each displayed hue is varied
from left to right in 16 evenly spaced steps ranging from "0"
(black) to full intensity.

The third screen uses attributes 20H through FFH to show how
colors can be varied in saturation.  As in the previous screen,
hue is varied in the vertical axis.  The 64 step range of color
saturation is shown from left to right in 16 evenly spaced steps
ranging from "no saturation" (pure white) to full color
saturation.

VGACOLOR, besides being a demonstration of the capabilities of
VGA/MCGA mode 19 (decimal) can be useful for setting the
brightness and contrast settings of your monitor.  It is also
an aid in convincing your spouse that the hundreds of dollars
that you spent on a VGA adapter and monitor were worth it.


NOTES ON MONITOR VERTICAL/HORIZONTAL SIZE SETTINGS

Depending on the brand and model of your display adapter and
monitor, the display vertical and horizontal size settings that
you determine using VGRID.EXE or VBOX.EXE may only be valid for
the VGA 640 x 480 mode.  Other screen resolutions may require
that the monitor be readjusted for the proper display aspect
ratio.

The reason for this is that different monitors can behave in
dissimilar ways as the video horizontal and vertical scan rates
are varied for different on-screen resolutions.  Normally, if
nothing is done by the monitor to compensate for these changes,
the size of the displayed image will vary considerably with scan
frequency.

Normally, this is not a problem with the standard VGA display
modes and VGA-only monitors.  The VGA standard specifies a
constant horizontal scan frequency of 31.5 KHz regardless of the
video mode, with a vertical scan rate of either 60 or 70 Hz.
Most VGA display adapters adhere to this, and most VGA monitors
expect this range of scan rates, and all is well.

However, problems can arise with some of the non-standard,
higher resolution "Super VGA" modes (800 x 600, 1024 x 768, and
the like) found in some display adapters when those modes are
used with the "multiscanning" or "multisync" monitors needed to
display the higher resolutions.  In the Super VGA modes, the
horizontal scan rate may be as high as 35 KHz, while the vertical
scan frequency may be as low as a flickery 50 Hz (this is done to
keep the overall video bandwidth down to something most monitors
can handle).  Different monitors deal with these changes in
horizontal and vertical scan frequencies in various ways.  Most
multiscanning displays have some sort of "autosizing" circuitry
built into them to maintain a constant image size despite changes
in scanning rates.  In some of these monitors, the autosizing
feature works very well, and once you have set the width and
height for one display standard, it is also correctly set for
other modes as well.  Other monitors have autosizing circuits
that do not work as well, or they may lack this feature entirely.
With these displays, you may have to reset the screen vertical
and horizontal size controls when switching between different
resolutions and display modes.

It is also possible that the centering of the image on your
monitor screen may vary with the resolution being displayed.
This is particularly true for the horizontal image position.
Some multiscanning monitors (such as the NEC Multisync II) have a
separate horizontal image centering control for each of several
horizontal scan frequency ranges.


QUESTIONS AND COMMENTS

You can leave questions or comments regarding these programs for
me on CompuServe (73710,2014).


-Arthur Stoppe
 July, 1989