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#54 -rv currently does not reverse colours of EPS figures
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nobody
5
2004-05-24
2004-05-24
Anonymous
No
Currently, xdvi -rv (or xdvi -fg white -bg black) only
reverses the
colours of the text, not the colours of the EPS diagrams*.
This results in bad fg/bg contrasts in those diagrams.
E.g.
an EPS diagram meant to be printed on white paper may
use dark-blue, dark-green and dark-red for drawing.
Such a diagram displays well and prints well on light
background.
However, they become unreadable when viewed using 'xdvi
-rv'
(for slide presentations). Preparing a separate EPS
diagram with
adjusted colours is tedious, and is indeed difficult
because
Ghostscript would change the bg/fg colours[*] when invoked
from xdvi.
Solution: better control of the colour handling of
Ghostscript:
-gsfg <colour> sets the foreground colour that
Ghostscript uses
-gsbg <colour> sets the background colour that
Ghostscript uses
-gsrv causes GS to reverse ALL colours
Then, we can display those diagrams nicely in reverse
video with:
xdvi -fg white -bg black -gsrv mydoc.dvi
A new hotkey "I" toggles the -gsrv feature on-the-fly.
Attached is a patch that has implemented these features.
The patch is against the CVS source checked out at
2004-05-24 13:38 (UTC).
It has been tested on a SuSE8.1 system, configured with
./configure --with-tetex
--with-default-texmf-path=/usr/share/texmf
--with-default-font-path=/var/cache/fonts//
Also tested with the "--disable-ps-gs" configure option.
Submitted by: Sau Dan LEE
<danlee@informatik.uni-freiburg.de
[*] Except for mono-colour EPS diagrams
using the default foreground colour (black) for drawing
and the default background colour (white) for erasing.
In this case, Ghostscript will substitute those colours
with the {fore,back}ground colours inherited from the
xdvi window.
Unfortunately, Ghostscript won't adjust any other colours.
patch < pathfile
Logged In: YES
user_id=177175
Thanks very much for your report and the patches. However
I'm still
not sure I've understood the problem correctly.
With the attached test file (test.tgz), an unpatched xdvi with:
xdvi -fg yellow -bg black
makes the foreground and the lines in the EPS file yellow,
which is
what I would expect. (On the other hand, with your patch,
the lines in
the EPS become black again - is that desired?)
But the green color of the `test' text, the blue rectangle
and the red oval are not affected by the -gs... options.
Do you maybe have an example for an EPS file with multiple
colors
as described in your report, and where using the -gs... options
does change the colors?
Logged In: NO
I'm Sau Dan LEE.
Yes, your file does display the rectangle in blue and
ellipse in red. The -fg/bg options changed the background
of the figure to black and the rims of the shapes to yellow,
but other colours remain.
But that is not always desirable. Your figure uses the
typical "programmer colours" (100% red, 100% green, blue,
cyan, magenta, yellow), which are visually bad because of
the poor contrast either against a light (e.g. white)
background and a dark (e.g. blue) background. e.g. your
text "test" is hard to read. That's why you don't notice
the problem.
A good colour scheme should make the things contrast well
(readable even if converted to grayscale). I'm giving a
patch file to your test.eps file to change the colours to
darkblue, darkgreen and darkred. This make the figure look
much better on white paper, because of the increased
contrast with white. Try to convert both to grayscale and
you'll see the difference! Now, the problem is: if I use
-bg black, the darkgreen text becomes unreadable. Darkgreen
text on a black background. That's terrible. The shapes
are still visible, but that's just because the rims are
drawn with yellow (due to -fg yellow). If the rims were
gone , then they're hardly visible.
Using my patch, you can add the "-gsrv" option to reverse
the colours of the EPS diagram. Volia. The rectangle now
shows up in light-yellow, which contrasts well with the
background. The ellipse is in light-cyan, which is also
eye-catching. The text is in light-magenta -- very readable
now. Yes, the original colours are replaced with new ones.
But that is what makes the text/background contrast high again.
Here is a patch to recolourize your figure:
--- test.eps.orig 2004-06-17 13:28:26.000000000 +0200
+++ test.eps 2004-06-17 13:34:38.000000000 +0200
@@ -14,15 +14,15 @@
/col1 {0.000 0.000 1.000 srgb} bind def
/col2 {0.000 1.000 0.000 srgb} bind def
/col3 {0.000 1.000 1.000 srgb} bind def
-/col4 {1.000 0.000 0.000 srgb} bind def
+/col4 {0.600 0.000 0.000 srgb} bind def
/col5 {1.000 0.000 1.000 srgb} bind def
/col6 {1.000 1.000 0.000 srgb} bind def
/col7 {1.000 1.000 1.000 srgb} bind def
/col8 {0.000 0.000 0.560 srgb} bind def
/col9 {0.000 0.000 0.690 srgb} bind def
-/col10 {0.000 0.000 0.820 srgb} bind def
+/col10 {0.000 0.000 0.520 srgb} bind def
/col11 {0.530 0.810 1.000 srgb} bind def
-/col12 {0.000 0.560 0.000 srgb} bind def
+/col12 {0.000 0.350 0.000 srgb} bind def
/col13 {0.000 0.690 0.000 srgb} bind def
/col14 {0.000 0.820 0.000 srgb} bind def
/col15 {0.000 0.560 0.560 srgb} bind def
Logged In: NO
Here is Sau Dan LEE again.
If you want good contrast PLUS yellow rims for the shapes, use:
xdvi -fg yellow -bg black -gsbg yellow -gsfg black -gsrv
(-gsrv has effect on -gsbg and -gsfg)
Logged In: NO
Here is Sau Dan LEE again.
If you want good contrast PLUS yellow rims for the shapes, use:
xdvi -fg yellow -bg black -gsbg yellow -gsfg black -gsrv
(-gsrv has effect on -gsbg and -gsfg)
Logged In: NO
Here is Sau Dan LEE <danlee@informatik.uni-freiburg.de> again.
If you want good contrast PLUS yellow rims for the shapes, use:
xdvi -fg yellow -bg black -gsbg yellow -gsfg black -gsrv
(-gsrv has effect on -gsbg and -gsfg)
Logged In: YES
user_id=177175
> Using my patch, you can add the "-gsrv" option to reverse
> the colours of the EPS diagram. Volia. The rectangle now
> shows up in light-yellow, which contrasts well with the
> background. The ellipse is in light-cyan, which is also
> eye-catching. The text is in light-magenta -- very readable
> now. Yes, the original colours are replaced with new ones.
> But that is what makes the text/background contrast high
again.
Thanks, I can see your point now. However there seems to be
a problem
with the implementation of the -gsbg flag; whith AFPL
ghostscript 8.10
(running at 24bpp), this leads to an unpleasant `flashing'
effect:
With the example file test.dvi, first a yellow background
appears
shortly at startup which is then overdrawn with black. You can
exacerbate this effect by toggling ghostscript anti-aliasing
via the
`V' keystroke; the image will then have wrong colors altogether.
I've attached a screenshot of the display (gsalpha.gif); can you
reproduce this problem?
screenshot of artefact with -gsbg after toggling `V'