When specified, tells xv to automatically issue a Dither
command whenever an image is first displayed. Useful on
displays with limited color capabilities (4-bit and 6-bit
displays), or in conjunction with the '-ncols'
option.
When specified, tells xv to automatically issue a Smooth
command whenever an image is first displayed. This is
useful when you are using one of the image sizing options
(such as '-expand' or '-max').
Forces xv to display the image in Raw mode.
Mainly used to override the autoDither or autoSmooth
resources. Can also be used to turn off the automatic
dithering and smoothing that occurs when you are using Use
Std. Colormap mode or when an image is shrunk to fit
the screen.
Tells xv to automatically crop the specified
region of the image. The rectangle is specified in image
coordinates, which remain constant (regardless of any
expansion/compression of the displayed image).
This is useful if you want to view a series of images,
and you only want to see one common area of the images.
For example, you may have the GIF weather maps of the
United States, but only want to display your general
region of the country.
Automatically rotates the image by the specified amount
whenever an image is loaded. deg can be 0, 90,
180, or 270. Positive values rotate the image clockwise,
negative values rotate the image counter-clockwise.
Makes the specified preset (in the xv color
editor) the default. It does this by swapping the
specified preset ( 1 , 2 , 3 , or 4
) with the settings associated with the Reset
button.
Forces the image to be displayed in greyscale. This is
most useful when you are using certain greyscale X
displays. While xv attempts to determine if it's
running on a greyscale display, many X displays lie,
and claim to be able to do color. (This is often because
they have color graphics boards hooked up to b/w
monitors. The computer, of course, has no way of knowing
what type of monitor is attached.) On these displays, if
you don't specify -mono , what you will see is a
greyscale representation of one of the RGB outputs of the
system. (For example, you'll see the 'red' output on
greyscale Sun 3/60s.) The -mono option corrects
this behavior.
Makes xv display a 'negative' of the loaded image.
White becomes black, and black becomes white. Color
images will have 'interesting' effects, as the RGB
components are individually reversed. For example, red
(255,0,0) will become cyan (0,255,255), yellow will
become blue, and so on.
Specifies the 'black' color used when the picture is b/w
stippled. (When '-ncols 0' has been specified,
or when viewing a b/w image.) Try something like: 'xv
-ncols 0 -bl red -wh yellow <filename>' for
some interesting, late-60's- style psychedelia
effects.
Turns on a 'slide-show' feature. Normally, if you specify
multiple input files, xv will display the first
one, and wait for you to give the Next command (or
whatever). The -wait option makes xv wait
for the specified number of seconds, and then go on to
the next picture, without any user intervention. The
program still accepts commands, so it's possible to
'abort' the current picture without waiting the full
specified time by using the Next command.
Note:
If you are in Use Std. Colormap mode, and you use -wait
0 , the images will not be dithered (as they
normally are when you are in Use Std. Colormap
mode). It's assumed that if you said '-wait 0'
that you want the images displayed at maximum speed. You
can still turn the dithering on if you desire by using
the -dither option.
Normally, when running a slide-show with the -wait
option, xv will terminate after displaying the
last image. If you also specify the -wloop
option, the program will loop back to the first image and
continue the slide-show until the user issues the Quit
command.
Makes xv display multiple image files in a random
order. Useful for breaking up the monotony of having
slide-shows always display in the same order. Also, if
you also use the -quit option, you can have xv
display a single, random file from a list of files. This
may be useful if you'd like xv to pick a random
'background image' from some set of files.
If you were on a PseudoColor display, xv used to
automatically clear the image window (and the root
window, if using a root mode) whenever you loaded a new
image. This was to prevent the potentially
annoying/confusing 'rainbow' effect that happens when
colormap entries are freed and reallocated with different
colors. This has changed. By default, xv no longer
clears the image/root window. This is for two reasons:
I've decided the rainbow effect is semi-entertaining, in
that it gives you something to look at while the next
image is being loaded. Secondly, if you are viewing a
series of images that have the same colors in them, it's
possible for xv to animate them (by using the '-wait'
command line option), albeit no faster than one frame
every 1-2 seconds. For example, you can go get the
satellite radar images from vmd.cso.uiuc.edu (in
the directory wx), run 'xv -wait 0 SA*',
and voila! Just like the evening news!
Whenever you load a new image, xv normally frees
the colors it was using for the previous image, and
allocates new colors for the new image. This can cause
'rainbow' effects on PseudoColor displays as the colors
are changed. You can avoid this problem entirely by using
the -nofreecols option, which suppresses the
normal freeing of old colors. This is most useful when
doing slide-shows. Note, however that there will be fewer
colors available for 'later' images. These images will
wind up being displayed with whatever colors were
allocated for the earlier images. As such, they may or
may not look that hot... (And allow me to reiterate: xv
is not an image animator, despite options like
these that let it do so, albeit poorly.)
Speeds up the performance of the xv load and xv
save windows. (Which are really the same window...)
It keeps xv from doing a stat() system
call for each file in the current directory whenever you
change directories. This is handy on systems with a lot
remote files, where doing the stat() calls takes
too long. One downside: subdirectories will not be shown
with the little folder icons, as it requires a stat()
call to determine whether a file is a subdirectory or a
data file. This will not affect the operation of the
program, just the 'niceness'.
Normally, xv uses the 'best' visual model it can
get. It looks for a 24 or 32-bit deep TrueColor,
or DirectColor visual. If it can get one, that's
what it uses. Otherwise, it will fall back to using the
'default' visual provided by your X server. You can
override this bit of cleverness by explicitly selecting a
visual to use. Valid types are StaticGray, StaticColor,
TrueColor, GrayScale, PseudoColor, DirectColor,
and default. All of these modes are not
necessarily provided on any given X display. Run xdpyinfo
on your display to find out what visual types are
supported. You can also specify a specific visual by
using its numeric visual ID, in the case that you have
multiple instances of a given visual type available ( xv
will pick the 'deepest' one by default)
Specifies an alternate cursor to use in the image window
(instead of the normal 'arrow' cursor). curs
values are obtained by finding the character number of a
cursor you like in the 'cursor' font. (Run 'xfd -fn
cursor' to display the cursor font.) For example, a curs
value of '56' corresponds to the (singularly useless)
'Gumby' cursor.
By default, xv prevents the image window from ever
getting larger than the screen. Unfortunately, because of
this, if you load an image that is larger than your
screen, the image will be shrunk until it fits on your
screen. Some folks find this undesirable behavior.
Specifying the -2xlimit option doubles the size
limitations. The image window will be kept from getting
larger than 2x the width and height of your screen.
Just
in case you're wondering why there are any size
limitations: it's fairly easy to accidentally ask for a
huge image to be generated. Simply Crop a section
of the image, zoom so you can see the individual pixels,
and UnCrop . If there were no size limitations,
the (expanded many times) image could be huge, and might
crash your X server. At the very least, it would take a
long time to generate and transmit to your X server, and
would freeze up your X server during part of it.
Generally undesirable behavior.
For the truly daring, this turns off all limitations on
the maximum size of an image. (Well, there's still an
X-imposed maximum size of 64K by 64K, but that really
shouldn't be a problem.) Warning: as mentioned above, it
is fairly easy to accidentally generate a huge image when
you do an UnCrop command, and you may well crash xv,
your X server, the host machine, or all three. Use At
Your Own Risk!!!
If specified, iconifying the xv image window will
automatically close all the other xv windows.
De-iconifying the xv image window will re-open the
other xv windows.
Specifies an initial directory for xv to switch to
when run. Also specifies the default directory used for
the visual schnauzer and the xv load and xv
save windows.
Tells xv to read a file fname that consists
of a list of names of image files to load, one per line.
This file is in the same format generated by the File
list checkbox in the xv save window. You can
use this to get around shell 'command-length' limitations
(which can hit you if you try 'xv *' in a
directory with a thousand or two files), or you could
have find (or whatever) generate this file based
on some type of criteria (age, size, etc.)
A kludge. In order to do certain operations, xv
needs to be able to precisely position the contents of an
image window on the screen. Unfortunately, window
managers disagree wildly on exactly how the "where's
the window" information will be presented to the
program. The practical upshot is that, despite a sizable
effort to the contrary, xv may very will have its
image window 'drift' on the screen as you resize it. This
option lets you specify correction factors to cancel out
the drift. If the window drifts down and to the right,
use negative values to cancel the drifting. If the window
drifts up and to the left, use positive values to cancel
the drifting.
Lets you specify the mono-spaced font used in the TextView
windows, and a few other places. Be sure you use a
mono-spaced font, or you may well get 'interesting'
effects.
Lets you change what string is displayed in the titlebar
of the image window. Normally, xv will display the
version number and the filename. If you're calling xv
from another program, you may prefer to have it print a
more descriptive string, or perhaps something like
'<click mouse to quit>' if you're also using the -quit
option.
For use when calling xv from some other program.
Forces all user input to be ignored. This keeps the
untrained (or inquisitive) user from nosing around,
creating files, or just generally misbehaving. Also note
that there's no way for the user to quit the program. It
is up to the calling process to manually kill xv
when it feels that the image has been displayed long
enough.
Turns file polling on. If enabled, xv will notice
when the currently displayed image file changes (due to
some other process rewriting it, or something like that),
and it will automatically reload the image file once it
appears to have settled down (once the file size stops
changing for a few seconds). See "Image Reloading"
for further details.
Normally, the visual schnauzer uses its own
private colormap. This is necessary in order to get a
good set of colors to display the image icons, and not
steal colors away from the actual image window. However,
you may find the colormap install/deinstall very
annoying. I do. You can specify this option ( +vsperfect
) to turn the 'perfect' behavior off. If you do so, the visual
schnauzer windows will steal away a small (64-entry)
part of the colormap (unless you are in Use Std.
Colormap mode, in which case they will share the
standard colormap). The downside is that neither the
schnauzer nor the image will look as good.
Completely disables the visual schnauzer. This is
mainly so, if you have vsPerfect turned off, you
can disable the schnauzer and keep it from stealing any
colors from the image. In the default setting ( vsPerfect
is turned on), this option will have no useful effect.
Sets the 'device' that the ghostscript package
will generate output for, which is used whenever you read
a PostScript file in xv. Currently, the default
device is ppmraw , which means all PostScript will
be converted to either a 24-bit color PPM file, an 8-bit
greyscale PGM file, or a 1-bit black- and-white PBM file,
as appropriate (based on the particular PostScript file
in question). Note that your copy of ghostscript
must be configured to support this device, and any other
values you may wish to set this option to. See the xvMakefile for further information.
Also note:
Be very careful when using these options, as it's pretty
easy to have ghostscript generate enormous
data files. For example, for normal 8" by 11"
pages, at 72dpi, a PBM file will require ~60K per page, a
PGM file will require ~500K per page, and a PPM file will
require ~1.5M per page. If you have it generate images at
300 dpi (see below), these sizes explode to roughly 1, 8,
and 24 megabytes per page. As such, you should forget
about viewing color pages at 300 dpi, and you may also
want to forget about viewing multi-page PostScript files
at 300 dpi.
Specifies the resolution of the page files generated by ghostscript,
in dots per inch. Defaults to 72 dpi. You can set it to
any value, but be careful about generating enormous
intermediate datafiles.
Sets the page size of the files generated by ghostscript.
Normally, this defaults to '612x792', which is the size
of 8" by 11" paper, as measured in 72nds of an
inch. Note that these numbers are in 72nds of an inch
regardless of the resolution (dpi) value set by gsResolution
.
Turns off certain decorations on the xv image window's
frame, maybe. Works for mwm, at least. There is no
way to do this trick with olwm, and twm
doesn't need it. Anyway, if you turn off the titlebar and
such on the xv image window, it removes the minimum
size constraint/problem that I talk about in "Cropping" ,
and elsewhere.
If specified, deletes all files specified on the xv
command line when xv exits. This can be handy if
you're using xv as an external viewer, and you'd
like to hand it a file, have it displayed, and then have
it go away.