rrw@naucse.cse.nau.edu (Robert Wier) (04/05/91)
OK, I'm confused. I have a situation where I'd like to display
monochrome graphics in at least 16 shades of gray, preferably
256 shades of gray. This is data received from the GOES series
of weather satellites.
Now, I've asked everyone here, but mostly people know about color
cga, ega, and vga boards. No one seems to be running monochrome.
I have several questions. It would seem reasonable that an EGA
board which can display 16 colors SHOULD be able to display 16
shades of gray. But I can't seem to be able to find anything
on whether this can acutually be done. We are running a variety
of boards, such as the EVEREX EV-659 and the Ultimate EGA. We
have multi-sync type monitors made by Mitsubishi and others.
We have software which indicates that we can run Hercules type
compatible b&w graphics. However, no where can I find a specification
of exactly what type of monochrome graphics should be available
(ie, 640 x 480 x 8 - which would give 256 shades of gray...)
Now, we have some high priced AT Vista cards in the graphics lab,
but that's really overkill. I just need something relatively
simple to display sat photos...
I'd GREATLY appreciate any guidence with this.
Please E-Mail or post
THANKS!
- Bob Wier
-------------- insert favorite standard disclaimers here ----------
College of Engineering
Northern Arizona University / Flagstaff, Arizona
Internet: rrw@naucse.cse.nau.edu | BITNET: WIER@NAUVAX | WB5KXH
or uucp: ...arizona!naucse!rrwdj@bragi.ctron.com (DJ Delorie) (04/05/91)
In article <3586@naucse.cse.nau.edu> rrw@naucse.cse.nau.edu (Robert Wier) writes: > > OK, I'm confused. I have a situation where I'd like to display > monochrome graphics in at least 16 shades of gray, preferably > 256 shades of gray. This is data received from the GOES series > of weather satellites. > I have several questions. It would seem reasonable that an EGA > board which can display 16 colors SHOULD be able to display 16 > shades of gray. An EGA board with a color monitor can display up to four shades of grey at a time. The reason? The TTL signals for an EGA supply two bits per color (R,G,B). Total of 64 colors, four of which are grey. An EGA with a MONOCHROME EGA monitor can display up to sixteen greys at a time, but the EGA card itself thinks they're colors. The monitor converts the TTL signals to greys instead of RGB. An EGA with a vanilla mono monitor (ie: from an MDA) is limited to four greys again, because the monitor only watches two of the TTL signals. A VGA can display up to 64 greys at a time, as it's palette has six bits per color, regardless of the type of VGA monitor you attach to it. This still gives you 192 pixel values left in 256 color mode to do simulated color if you want. Of course, 16 greys in 16-color mode is no problem for VGA. DJ dj@ctron.com
osmoviita@cc.helsinki.fi (04/07/91)
In article <1399@bragi.ctron.com>, dj@bragi.ctron.com (DJ Delorie) writes: > In article <3586@naucse.cse.nau.edu> rrw@naucse.cse.nau.edu (Robert Wier) writes: >> >> OK, I'm confused. I have a situation where I'd like to display >> monochrome graphics in at least 16 shades of gray, preferably >> 256 shades of gray. This is data received from the GOES series >> of weather satellites. .... > > A VGA can display up to 64 greys at a time, as it's palette has six > bits per color, regardless of the type of VGA monitor you attach to > it. This still gives you 192 pixel values left in 256 color mode to > do simulated color if you want. Of course, 16 greys in 16-color mode > is no problem for VGA. > > DJ > dj@ctron.com Some newer SuperVGA cards like Orchid ProDesigner II have 6/8 bit DACs, so they should be able to show 256 shades of gray if you know how to switch from 6 bit mode to 8 bit mode. I don't know and if someone can tell please do it. Orchid PD II is a Tseng ET4000 based card. Kari Osmoviita
joe@proto.com (Joe Huffman) (04/09/91)
dj@bragi.ctron.com (DJ Delorie) writes in an otherwise flawless posting: >An EGA with a vanilla mono monitor (ie: from an MDA) is limited to >four greys again, because the monitor only watches two of the TTL >signals. EGA mode 0x0F (for use with the "vanilla ... MDA") has four "colors". Black, white (green on the IBM 5151), high intensity white, and blink. Blinking pixels on the screen would appear to have little use in simulating another shade of grey. -- joe@proto.com
dj@bragi.ctron.com (DJ Delorie) (04/09/91)
In article <1991Apr08.184731.8800@proto.com> joe@proto.com (Joe Huffman) writes: >dj@bragi.ctron.com (DJ Delorie) writes in an otherwise flawless posting: > >>An EGA with a vanilla mono monitor (ie: from an MDA) is limited to >>four greys again, because the monitor only watches two of the TTL >>signals. > >EGA mode 0x0F (for use with the "vanilla ... MDA") has four "colors". >Black, white (green on the IBM 5151), high intensity white, and blink. >Blinking pixels on the screen would appear to have little use in simulating >another shade of grey. You can shut off the blink with a BIOS call (or if not, through hardware), giving you: black "intense" (dim) normal normal & "intense" The monochrome monitor has two digital inputs, for a total of *four* intensity levels. The EGA card is capable of driving the lines in all four states, giving four available intensity levels. The *default* behavior, however, is to simulate blinking for the benefit of backward compatibility. I know it works this way because I wrote a graphics terminal emulator that used EGA, vanilla Mono monitor, and mode 0x0f, and it produced four levels of intensity - and no blinking. DJ