Garbo/Garbo.cdr/pc/gifutil/vgaimg12.arc/VGAIMAGE.DOC

Text File | 1989-11-15 | 20KB | 429 lines

VGAIMAGE    Version 1.2   11/12/89

  By: Hoke Johnson

VGAIMAGE is a shareware image viewer/maker program for the IBM PC.  It is
optimized for use with VGA cards and monitors but allows viewing of Gif images
on EGA monitors but currently is really only good for 16 color EGA Gif
pictures.  VgaImage was created to provide many additional image viewing
features which I haven't been able to find in other image viewing programs.
This is the third release of VGAIMAGE and it currently supports GIF and TIFF
file formats.

NEW FEATURES:

  VGA 360x480x256 mode support for standard VGA

  VGA 320x400x256 mode support for standard VGA

  Virtual Screen Disk Buffer to process files larger than VGA screen.

  50 percent reduction works on more modes.

FEATURES:

  Gif file viewing and processing

  Viewing and processing of 2, 16 and 256 level B&W Tiff files

  Conversion of Halftoned and 16 level Tiff files to 64 level Gif files
  Conversion of 256 level Tiff files to 256 level Gif files

  Support for Paradise VGA boards in 640x400x256 mode

  High Resolution VGA Support for Tseng Labs VGA boards (Orchid Designer VGA)
  and Paradise VGA boards

  Zoom mode support for Tseng Labs VGA boards

  360x480x256 and 320x400x256 mode support for standard VGA boards

  16 level Gray Scale display of Gif files on normal VGA boards at 640x480

  16 level Gray Scale display of Gif files on Tseng Labs boards at 1024x768

  50% size reduction on large Gif files to fit them on the screen and ability
    to write them as reduced size Gif files

  Gif and Tiff header display

  Brightness controls

  Smooth Vertical scrolling of large images

  Setting of the number of bits of resolution to be used for the RGB primaries
    (Between 1 and 6 bits of resolution)

STARTUP PARAMETERS:

  Usage: vgaimage [GCType]

  Where GCType is: one of the following graphic card types:
    EGA, SUPEREGA, VGA, DESIGNERVGA, PARADVGA

  Graphic card type can also be changed once the program is running by pressing
  the "D" key.

HARDWARE REQUIREMENTS:

  IBM PC with at least 256K memory and a VGA or EGA graphics card and suitable
  monitor.  The graphics card should also have at least 256K of memory.  A
  hard disk is not required but is recommended if the Virtual Disk Buffer is
  used since it performs a large number of I/O,  a large RAM disk works even
  better.

  This program works well with standard VGA cards,  VGA cards based on the
  Tseng labs chip set (such as Orchid Designer VGA cards etc) and on Paradise
  VGA boards.  With the standard VGA card, resolutions of 320x200x256,
  320x400x256, 360x480x256 and 640x480x16 shades of gray are possible. With
  the Tseng labs based cards all the modes of the standard VGA card are
  possible plus 640x480x256, 800x600x256 and 1024x768x16 shades of gray.  With
  the Paradise VGA cards all the modes of the standard VGA card are possible
  plus 640x400x256 colors.  The extended modes of the Tseng labs based cards
  (800x600x256 and 1024x768x16) require multi-sync monitors.


USING VGAIMAGE

  Once VGAIMAGE is started, a list of available files for viewing is displayed
  in the file section which is the upper 2/3 of the screen and a control panel
  is displayed in the control section which is the lower 1/3 of the screen.

  The file section is used to select files for viewing or conversion and the
  control section is used to control the way files are displayed and converted.
  The file selection contains a list of available files that match the input
  file type.  File types currently supported are Tiff and Gif,  Tiff files must
  have an extension of .TIF and Gif files must have an extension of .GIF .
  Change the highlighted file by using the cursor arrow keys as well as the
  home and end keys.  With desired file selected press the enter key to view
  the selected file,  when done viewing press the enter key again to return to
  file selection mode.  Currently the first 120 files in the current directory
  are available for viewing.

  The control section shows the current state of the display control variables.
  Each variable is preceded by a description and an upper case letter in
  parentheses.  The state of the variable is changed by depressing the letter
  in parentheses,  either upper or lower case.  For example:

     Display Type   (D): VGA

     This example shows that the current display type is VGA and to change to
     another display type,  press the "D" key to sequence through all possible
     display types.

  The available control variables and other keys that do things are described
  below:

  F1 - Help Screen

  I  - Changes the input file type for viewing.  Currently GIF and TIFF are
       supported.  Files must have extensions .GIF and .TIF respectively.

  O  - Changes the output file type to be written during a write command.
       Currently only GIF is supported.

  F9,\ Change directory.  Press F9 or \ and then respond with the desired new
       directory followed by a Carriage Return.

  D  - Change the display type.  Pressing the "D" key sequences through all
       the currently supported Graphic Card types.

  A  - Aspect adjustment flag on/off. The aspect adjustment flag is normally
       on and affects the display when the display type is set to standard
       VGA and the 360x480x256 mode is being used.  The result is that every
       other pixel in the horizontal dimension is discarded.  Normal aspect
       GIF files such as 640x480 images should be viewed with this flag on,
       there are some GIF images that have a 360x480 size with the aspect
       already adjusted, these should be viewed with the aspect flag off.

  H  - Causes the file header contents to be displayed prior to the image
       being displayed.  Header remains displayed until an "enter" or CR is
       pressed.

  L  - Causes the display program to shrink the displayed image by 50% in both
       the horizontal and vertical directions.  This mode now works in VGA
       320x200 mode as well as some of the super VGA modes such as 640x480,
       800x600 and 640x400.  It doesn't work in 360x480x256 mode.

  E  - Changes to a 16 level gray scale display mode for Gif files.  For
       normal IBM VGA type boards this gives a 640x480 display with 16 levels
       of gray.  With Designer VGA boards (Tseng Labs) it is possible to
       switch between 640x480 and 1024x768 modes at 16 levels of gray by using
       the F8 key.

  F8 - High Resolution Lock mode.  This is only usable with the Designer VGA
       type boards or boards with Tseng Labs chips.  This gives 800x600 and
       256 colors with the VGA 16 color B&W mode disabled (E key) and
       1024x768 and 16 levels of gray with the VGA 16 color B&W mode enabled.
       (A multisync monitor is also required)

  F10 or ESC are used to exit from VGAIMAGE.

  S  - Sets internal special flag which allows a modified Orchid Designer VGA
       board to display 800x600x256 mode properly.  Normally this setting
       should be left alone (ie OFF), if anyone is interested, write me for
       details.

  G  - In Gif view mode this key selects the number of bits of resolution for
       each primary color to use when viewing.  In Tiff view mode this key is
       used to select the number of levels of gray to use when the Tiff file
       is displayed.  This value can be 2, 16, 64 or 256.  Not all Tiff files
       can be viewed in all possible levels of gray output.

       The supported Tiff renderings are:

           2 level Tiff to   2 level display
           2 level Tiff to  64 level display
          16 level Tiff to  16 level display
          16 level Tiff to  64 level display
         256 level Tiff to 256 level display

  V  - Virtual Disc Buffer Enable/Disable.  When the Virtual Disc Buffer is
       enabled,  the bytes of each scan line as they are read from either a GIF
       or a Tiff file are written into a disc file VGAIMAGE.VRT.  This allows
       images larger than the available screen memory to be processed.

COMMANDS WHILE IMAGE IS BEING VIEWED

  B  - Changes image to BW equivalent picture

  C  - Restores original color picture

  T  - Decreases the number of bits of resolution for each primary. Values
       supported are 1 to 6 bits of resolution.  This can be used to get a
       rough idea on the amount of resolution that a given image has by
       starting out at the maximum and reducing until you can see a
       deterioration in the image quality.

  G  - Complement to the T command,  increases the number of bits of
       resolution for each primary.

  +  - Increase the brightness of the displayed image.

 (-) - Decrease the brightness of the displayed image.

  0  - Restore image to its original brightness (Zero key)

  W  - Writes the currently displayed image in the specified outfile format.
       Currently only GIF is supported.  The actual image can be longer than
       the display screen,  for instance 640x819 for the Designer VGA card.
       Large files can be output in GIF format in a minute or two on an AT
       machine.  The output filename of the new file is the same as the first
       filename with the new extension if we are converting from one file type
       to another.  If the intended new filename already exists,  a new
       filename is used which has the last letter of the filename
       "incremented".

       If the Virtual Disc Buffer is not enabled,  VGAIMAGE reads the image
       from the display memory and creates the output file,  this works for
       VGA 320x200x256, DESIGNERVGA 320x200x256, 640x350x256, 640x480x256,
       800x600x256 modes.  If "W" is pressed without Virtual Disc Buffer
       enabled and a display mode other than those just mentioned is in use,
       VGAIMAGE terminates the display of the current image and returns to
       the file selection menu.

       If the Virtual Disc Buffer is enabled,  VGAIMAGE reads the image from
       the Virtual Disc Buffer file VGAIMAGE.VRT and creates the output file.
       The Virtual Disc Buffer only functions when the display type is one of
       VGA, DESIGNERVGA or PARADVGA.  Images larger than the display can be
       handled with the Virtual Disc Buffer.

       Currently you can tell that the GIF write process is in progress by
       the disk busy light,  the completion of the write process is signalled
       by two short beeps.

  Z  - Turns Zoom mode on and off for Tseng boards (Designer VGA)

  <  - Decrease Zoom factor (actually the "," key)

  >  - Increase Zoom factor (actually the "." key)

       While in Zoom mode you can scroll around the picture by using the
       Home, PGup, PGdn, and cursor arrow keys.

  M  - Smooth vertical scrolling of images which are larger than the display
       screen.  This is usable on Designer VGA boards and VGA boards with
       images that have a height greater than 480 lines.

NOTES ON USING THE VIRTUAL DISC BUFFER

  The Virtual Disc Buffer is a disc based copy of the pixels which make up
  an image.  It allows for images larger than the display memory to be
  converted or processed.  It also allows for images which VGAIMAGE can't
  readback from display memory to be converted or processed.  The virtual disc
  buffer should only be enabled when you want to output a GIF file such as when
  you are converting from Tiff to GIF or when you are adjusting the brightness
  on a GIF file or doing a 50% reduction on a GIF file.  If the virtual disk
  buffer is enabled all the time,  VGAIMAGE will operate much slower due to
  the great increase in extra I/O.  A file VGAIMAGE.VRT is created in the
  current directory and used as the virtual disc buffer,  upon exit of
  VGAIMAGE, the file VGAIMAGE.VRT is left and is not deleted,  if space is a
  problem, be sure to delete the VGAIMAGE.VRT files.  The virtual disk buffer
  shouldn't be with a floppy drive unless you are prepared to wait a very
  long time since the virtual disc buffer requires a lot of I/O.  For best
  results use with a large Ram Disc or a fast hard disk.

  VGAIMAGE can read interlaced images but normally only outputs non-interlaced
  images.  The one exception is for a GIF image which is already interlaced and
  is displayed with the virtual disk buffer enabled,  a subsequent write of that
  image will be as an interlaced image.

NOTES ON VIEWING TIFF FILES AND MAKING GIF FILES FROM TIFF FILES

  Black and White Tiff files can be viewed and converted into Gif files.  Tiff
  file support is currently only available for VGA type boards.  Tiff files
  with 1 bit per pixel, 4 bits per pixel and 8 bits per pixel are supported.

  When viewing Tiff files with 1 bit per pixel, and Tiff Gray Levels set to
  64, VGAIMAGE converts to an image with 64 levels of gray.  In doing so the
  pixel width and height of the original Tiff Image is reduced by a factor of
  eight.  For instance a 1 bit per pixel Tiff image with a width of 4800
  pixels and a height of 6400 pixels will reduce to an image with a width of
  600 pixels by a height of 800 pixels where each pixel has six bits per
  pixel.  It is also possible to view Tiff images without the conversion to 6
  bits per pixel by setting the Tiff Gray Levels to 2 by pressing the G key.
  Currently it is not possible to make a valid Gif file when there is only one
  bit per pixel.

  When viewing Tiff files with 4 bits per pixel, VGAIMAGE can display an image
  with either 16 or 64 levels of gray.  The Tiff Gray Levels setting controls
  which mode is used (G key).  When viewing Tiff files with 4 bits per pixel
  and 64 levels of gray displayed, the height and width of the image is
  reduced by a factor of 2, thus a 1200 x 960 image will reduce to 600 x 480.

  VGAIMAGE has been tested with a few 256 level Tiff files,  this type of Tiff
  file should produce the best results.  The 6 bit per primary limitation of
  the VGA card causes the displayed image to be of only 64 levels but the full
  resolution is maintained when creating an output GIF file.  (If the 256
  level Tiff file is brightened or darkened prior to saving as a GIF then the
  gray scale levels will be rounded off to 6 bits or 64 gray levels in the
  palette)

  VGAIMAGE has been tested with Tiff files created by HP Scanning Gallery and
  with Tiff files created by HALO DPE.  Good image results are achieved by
  using HP Scanning Gallery,  using the Fatting Dither setting and a custom
  resolution of 600 dots per inch.  Experiment with setting the brightness
  control to "Lighten" and "Normal" to find the best result.  This allows a
  normal A size sheet of paper to be scanned and produces an image of
  approximately 600 x 800 with 64 levels of gray.  Normally it is necessary to
  brighten the image by pressing the "+" key approximately 6 to 10 times prior
  to saving the image as a Gif file.  The Tiff files produced using this
  method vary from 2.5 to 4.4 Megabytes but can be compressed using one of the
  available "archiving" utilities to produce files < 1.2 Mbytes which allows
  them to be stored on 1.2 M floppies and thus moved between machines.  Images
  can be produced using the 16 levels of gray however I have found that the
  images are usually darker and need to be brightened so much that you loose
  image quality.  The 16 levels of gray would probably do well on a picture
  that was very bright to start with.  Images that are dark to start with
  generally don't scan well.

SHAREWARE:

  VGAIMAGE is user supported software.  VGAIMAGE is made available for a
  free ten day trial period.  If you find VGAIMAGE useful,  you may license
  the program for non-commercial use on one machine by sending $15.00 to:

              Hoke Johnson
              P.O. Box 35602
              Monte Sereno, CA 95030

  All other rights reserved.

  VGAIMAGE may not be modified in any way by anyone other than the author.
  VGAIMAGE may be freely distributed to others only in its complete and
  unmodified form with no fee charged other than postage, media or
  duplication charges.

  Regardless of how your copy of VGAIMAGE was obtained,  it is requested
  that you comply with the above licensing agreement.

  All warranties are disclaimed,  including damage to hardware and/or
  software from use of this product.

FUTURE ENHANCEMENTS

  The following are some of the planned future enhancements:

  -Support for more types of high resolution VGA boards

  -Color GIF file creation from scanned Tiff files

  -Pseudo 640x400x256 color mode on standard VGA

  -Better error checking during GIF decoding

  -PCX file format support

  -Support for more types of TIFF files (64 gray level)

  -Test escape (ESC) key during image decoding or writing to abort current
   action.

FEEDBACK AND COMMENTS

  I welcome your comments, you can contact me by mail

              Hoke Johnson
              P.O. Box 35602
              Monte Sereno, CA 95030

  For now,  I do not plan on trying to support compressed Tiff files since the
  packages I have seen have the option of specifying whether the output Tiff
  file is compressed or not and the compression efficiency is not that good
  anyway.

KNOWN BUGS, FEATURES OR LIMITATIONS:

  - When using virtual disk buffer, a file VGAIMAGE.VRT is created in the
    currently selected directory,  this file is not deleted when VGAIMAGE
    terminates and thus the temporary file VGAIMAGE.VRT is left undeleted.
    This file contains a sequence of bytes which are the values of the pixels
    for the last image which was decoded while the virtual disk buffer was
    enabled.  A source for the uncompressed bytes of a Gif image.
  - Empty Gif files are created in the current directory.  This happens when
    trying to write a Gif file and the Virt Disk Buffer is not enabled and the
    display mode is one which cannot be read.  For example displaying in
    Paradise 640x400 mode with the Virt Disk Buffer disabled.
  - Some modes don't vertically scroll or pageup and pagedown smoothly and
    tend to cause the picture to jump sideways, this happens on the PARADVGA
    mode.
  - When using the 50% reduction and vertically moving the picture with either
    the pageup/pagedown keys or the "m" key, the scrolling continues on beyond
    the bottom of the picture and sometimes the top of the picture will start
    to appear at the bottom only shifted sideways.  This also happens on the
    1024x768x16 B&W mode on the Designer VGA.
  - 2 level Tiff files can be viewed but cannot be saved correctly as GIF files.

CHANGES:

VGAIMAGE Version 1.0,  03/27/89 - Initial Release

VGAIMAGE Version 1.1,  05/15/89

  - Fixed problem which didn't sort directory listing properly when there
    were only two files to be displayed
  - Enhanced GIF output routine to produce maximally compressed files and
    improved speed drastically by using hashing and improving the disk
    i/o routines.
  - Added support for displaying 640x400x256 colors on the Paradise VGA
    board.
  - Decreased the amount of memory required for displaying very large GIF
    files.
  - Added additional Tiff Tag handling and allowed program to attempt to
    display image even if there are some unhandled tags.  A list of
    unhandled tags is also listed when the Header display is enabled.
  - Added support for 256 level Tiff files

VGAIMAGE Version 1.2,  11/12/89

  - Allow files to be opened which are secured as read-only
  - Fixed error handling of opening invalid Tiff files
  - Added Virtual Screen Disc Buffer support which allows image conversion
    on images which exceed the size of the display memory.
  - Added support for 360x480x256 and 320x400x256 modes on the standard VGA
    card.  For the 360x480x256 mode there is an aspect adjustment flag which
    allows 640x480x256 images to display.
  - Added line clipping when displaying images larger than the screen.
  - Added support for 50 percent reduction on super VGA modes such as
    640x480x256, 800x600x256 and 640x400x256.