Re: FVWM: fvwm2 - xv can't grab screens

From: Grant McDorman <grant_at_isgtec.com>
Date: Fri, 29 May 1998 13:07:00 -0400

According to Kendrick Vargas:
> On Thu, 28 May 1998, Marc D. Williams wrote:
>
> > > Don't know ... I've never had trouble with xv, even on many many platforms.
> > > You could use xwd in the meantime.
> >
> > It's me again. Just now I got around to playing with the screen grab
> > stuff and am still having problems.
> > As I mentioned before, xv (3.10a) will not grab fvwm2 screens but has
> > no problem with other window managers. Running at 1024x768, 16bpp.
> > I now get errors that I never received before. I'm in DOS now so
> > I sorta forgot it. :-) Something like 'can't grab 0,0 1024x760'.
> >
> > Anyway, tried xwd as mentioned. Xwd created images that are near black
> > so they're useless. Almost like someone turned out the lights on the
> > image. This happens with other wm's also.
> > Just read on a newsgroup that xwd doesn't support above 8bpp.
> > Is this true?

Both xv and xwd don't work with mixed visuals - i.e. if your default visual
is 8bpp, but you're grabbing windows that are 16 or 24 bits deep. If that
isn't the case, then they're fine; if, on the other hand, you do have that
case you get what you described - black images. They both work with 24 bits
- or, at least, the vanilla X11R6.3 and Solaris 2.5 xwd work with 24 bits. I
do not know about 16bpp.

ImageMagick, on the other hand, handles mixed visuals with no problem. (The
command-line utility to do a screen grab in ImageMagick is 'import'; grabs
can also be done with 'display'.) I use ImageMagick because of this, and
also because it supports more image formats (not to mention being actively
maintained...).

Note, also, that with your 16bpp display could be TrueColour or
PseudoColour. In the latter case, you have a (rather large) colourmap; it is
unlikely that xv and xwd would expect to get a 64K colourmap instead of the
usual 256.

You can find out what your default visual is with 'xdpyinfo', and you can
find out what a particular window is with 'xwininfo'.

I will try to fix the VNC X server to work with 16bpp and test xv, xwd, and
ImageMagick with that later today.

> > Any suggestions on another app with screen grab features?
> > Not sure if KDE's ksnapshot would work outside of KDE (don't ksnapshot
> > yet anway).
>
> Well, I've never found XV's screen grab utils to be very stable (shame
> tho). I don't like KDE so I wouldn't suggest it... I don't think XWD works
> with anything better than 8bit displays.
>
> My suggestion would be to use GIMP ... as early as the 0.99.29 release of
> GIMP, there's been a grabbing (screen, window, rubberband) feature.

GIMP - at least early versions I tried - did not work at all with
non-TrueColour displays (it made invalid assumptions about what could be
done with colourmapped displays). If your display is TrueColour, then it's
feasible; otherwise, I wouldn't suggest it.

-- 
Grant McDorman <grant_at_isgtec.com>
ISG Technologies, Inc.  http://www.isgtec.com
Mississauga, Ontario, Canada


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Received on Fri May 29 1998 - 12:17:45 BST

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