| Re: pixmap problem [message #36220 is a reply to message #6988] |
Thu, 28 August 2003 11:47   |
Steve Ready
Messages: 6
Registered: July 2000
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Junior Member |
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I have replicated this with a Radion VE 32mb, Invidia GForce 64mb, and a
Matrox 32mb under Win2k and XP. The maximum image size returned by the
correct behavior for all these boards seems to scale loosely with the color
resolution (16 versus 32 bit) coupled with the amount of card memory. It
would be nice to have a better understanding of this and have IDL correctly
report the limitiations.
I have reported this to RSI and here was their response:
********************************************
We have no reason to believe that you are running into any issue other than
the limits imposed by the Windows O.S. in its interface with your graphics
card. One way to see this would be to try to make a bigger PIXMAP with the
Windows Visual C++/MFC API. In both cases, you would want to make sure that
both IDL and the MFC comparative program would have a "virgin" O.S.
environment; that is, there would not be other applications running about in
the background making demands on the video card memory. Consider that video
card memory could get fragmented just like process memory.
IDL's WINDOWS, /PIXMAP call is making a basic call on the Win32 API pixmap
library. I do not know the underlying source code for Microsoft's library,
but it is very possible that that memory automatically makes a 3x or 4x
pixmap-coordinates demand on the video card. Perhaps it does this only when
your display is set to true color; you could test and see if setting your
display to 256-colors provided you the bigger pixmap you want.
We would expect the larger memory video card to allow for a much larger
maximum PIXMAP size, but, to be certain, you may need to consult with the
video card vendor about what THEY think the maximum pixmap is that Windows
can make on their card.
***************************************************
"Karl Schultz" <kschultz_no_spam@rsinc.com> wrote in message
news:vksds6nnjrv1a@corp.supernews.com...
>
> This is a known problem, # 22066 should you call IDL tech support about
it.
>
> There is no clear resolution to the problem, but it does appear to be
pretty
> sensitive to the graphics card and/or driver software. On many machines,
> the attempt to create a "too large" pixmap will fail and any pixmap that
is
> created successfully returns the correct data on a TVRD; this is the
correct
> behavior. However, several users have reported the same symptoms as you
are
> describing. If you can report what graphics hardware and driver software
> (including version information) you are using, perhaps we can identifiy a
> pattern. (And I suppose the canned response of "check your drivers for an
> update" is a good thing to offer here as well.)
>
> Another strange behavior on the failing hardware is that the ORDER keyword
> can affect the pixmap size threshhold where the data is not read back
> correctly via TVRD. IDL itself does not perform the "flip" as controlled
by
> ORDER. IDL instead modifies parameters to a WIN32 GDI call, thus making
the
> GDI or graphics driver perform the flip. A change in behavior like this
is
> somewhat suggestive of a driver problem.
>
> Karl
>
>
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