Inverting command line session colours

Inverting command line session colours

[Laura Lazzati]

Hi Guix!

I am having trouble inverting the colours of the command line session
videos. They should be black in the foreground with white text.
Gábor, I guess you solved that, could you remind me how you did it?
There was a link with -negate in convert but did not work for me.

Regards :)
Laura

Re: Inverting command line session colours

[Gábor Boskovits]

Hello Laura,

> I am having trouble inverting the colours of the command line session
> videos. They should be black in the foreground with white text.
> Gábor, I guess you solved that, could you remind me how you did it?
> There was a link with -negate in convert but did not work for me.
>

Here is a command that works for me:

convert xyz.ps -background white -flatten -negate xyz.png

> Regards :)
> Laura

Best regards,
g_bor

Re: Inverting command line session colours

[Laura Lazzati]

Hi!
> convert xyz.ps -background white -flatten -negate xyz.png
I had already tried the -negate before but didn't work, I only got
full white pngs (the text turned white)
I am running  imagemagick    6.9.10-14 this is the rule:
-------------starts----------------
(VIDEO)/$(LOCALE_LANG)/out/$(SESSION)-%.png:
$(VIDEO)/$(LOCALE_LANG)/out/$(SESSION)-%.txt
    tail -n 20 $< | \
    paps --landscape --columns=80 --font "Monospace 20" | \
    convert -density 128 \
            -fill black \
            -background white \
            -flatten \
            -rotate 90 \
            -delete 0--2 - $@
-------ends-------------------

Re: Inverting command line session colours

[Björn Höfling]

[-- Attachment #1.1: Type: text/plain, Size: 2976 bytes --]

Hi Laura,

this kept me awake, I had to open my laptop again :-)

On Fri, 8 Feb 2019 19:53:50 -0300
Laura Lazzati <laura.lazzati.15@gmail.com> wrote:

> Hi!
> > convert xyz.ps -background white -flatten -negate xyz.png  
> I had already tried the -negate before but didn't work, I only got
> full white pngs (the text turned white)
> I am running  imagemagick    6.9.10-14 this is the rule:
> -------------starts----------------
> (VIDEO)/$(LOCALE_LANG)/out/$(SESSION)-%.png:
> $(VIDEO)/$(LOCALE_LANG)/out/$(SESSION)-%.txt
>     tail -n 20 $< | \
>     paps --landscape --columns=80 --font "Monospace 20" | \
>     convert -density 128 \
>             -fill black \
>             -background white \
>             -flatten \
>             -rotate 90 \
>             -delete 0--2 - $@
> -------ends-------------------

I can confirm this problem, let's track it down the Guix way:

## Make sure we are really talking about the same, getting into a fresh
container of latest guix:

# To make sure you are at the same commit where I tested this, you
could do a:
$ guix pull --commit=307182d4f7b1a56e220f208ad5f886e7784db115

$ guix describe
Generation 46	Feb 08 2019 23:58:31	(current)
[.. other channels here ..]
  guix 307182d
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: 307182d4f7b1a56e220f208ad5f886e7784db115

$ cd /tmp
$ mkdir tst
$ cd tst
# really get into a container, to be extra sure!
/tmp/tst$ guix environment -C --ad-hoc coreutils less imagemagick paps

$ convert -version
Version: ImageMagick 6.9.10-14 Q16 x86_64 2018-11-14 https://imagemagick.org
Copyright: © 1999-2018 ImageMagick Studio LLC
License: https://imagemagick.org/script/license.php
Features: Cipher DPC OpenMP 
Delegates (built-in): bzlib fftw fontconfig freetype gvc jng jpeg lcms lzma pangocairo png tiff x xml zlib

# Create a postscript file we can work with:
$ echo "Hello, World!" | paps --landscape --columns=80 --font "Monospace 20" > hello-world.ps

# This output looks good, white background, black text:
cat hello-world.ps| convert -density 128 -fill black -background white -flatten -rotate 90 -delete 0--2 - out.png

# Though I'm getting this warning, is that the problem?:
# convert: profile 'icc': 'RGB ': RGB color space not permitted on grayscale PNG `out.png' @ warning/png.c/MagickPNGWarningHandler/1667.

# This produces only whiteness:
# Same warning as above:
cat hello-world.ps| convert -density 128 -fill black -background white -flatten -rotate 90 -delete 0--2 -negate - out-negated.png

#But at least this works afterwards: White text on black background:
convert out.png -negate outout.png



Conclusion: As a quick workaround, you can add another pipe and use
convert twice.

But there should be a way to do it in one way. ImageMagick is a bit
tricky in that. I have no idea for now.

As reference, I'm attaching my output files.

Björn


[-- Attachment #1.2: hello-world.ps --]
[-- Type: application/postscript, Size: 10321 bytes --]

[-- Attachment #1.3: out.png --]
[-- Type: image/png, Size: 4213 bytes --]

[-- Attachment #1.4: out-negated.png --]
[-- Type: image/png, Size: 1185 bytes --]

[-- Attachment #1.5: outout.png --]
[-- Type: image/png, Size: 2079 bytes --]

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 195 bytes --]

Re: Inverting command line session colours

[Laura Lazzati]

Go to bed Bruno :) I will be writing another mail, and answer back
this one. but go to bed! your intern will tell Sage, you have to
recover from your cold.
On Fri, Feb 8, 2019 at 8:44 PM Björn Höfling
<bjoern.hoefling@bjoernhoefling.de> wrote:
>
> Hi Laura,
>
> this kept me awake, I had to open my laptop again :-)
>
> On Fri, 8 Feb 2019 19:53:50 -0300
> Laura Lazzati <laura.lazzati.15@gmail.com> wrote:
>
> > Hi!
> > > convert xyz.ps -background white -flatten -negate xyz.png
> > I had already tried the -negate before but didn't work, I only got
> > full white pngs (the text turned white)
> > I am running  imagemagick    6.9.10-14 this is the rule:
> > -------------starts----------------
> > (VIDEO)/$(LOCALE_LANG)/out/$(SESSION)-%.png:
> > $(VIDEO)/$(LOCALE_LANG)/out/$(SESSION)-%.txt
> >     tail -n 20 $< | \
> >     paps --landscape --columns=80 --font "Monospace 20" | \
> >     convert -density 128 \
> >             -fill black \
> >             -background white \
> >             -flatten \
> >             -rotate 90 \
> >             -delete 0--2 - $@
> > -------ends-------------------
>
> I can confirm this problem, let's track it down the Guix way:
>
> ## Make sure we are really talking about the same, getting into a fresh
> container of latest guix:
>
> # To make sure you are at the same commit where I tested this, you
> could do a:
> $ guix pull --commit=307182d4f7b1a56e220f208ad5f886e7784db115
>
> $ guix describe
> Generation 46   Feb 08 2019 23:58:31    (current)
> [.. other channels here ..]
>   guix 307182d
>     repository URL: https://git.savannah.gnu.org/git/guix.git
>     branch: master
>     commit: 307182d4f7b1a56e220f208ad5f886e7784db115
>
> $ cd /tmp
> $ mkdir tst
> $ cd tst
> # really get into a container, to be extra sure!
> /tmp/tst$ guix environment -C --ad-hoc coreutils less imagemagick paps
>
> $ convert -version
> Version: ImageMagick 6.9.10-14 Q16 x86_64 2018-11-14 https://imagemagick.org
> Copyright: © 1999-2018 ImageMagick Studio LLC
> License: https://imagemagick.org/script/license.php
> Features: Cipher DPC OpenMP
> Delegates (built-in): bzlib fftw fontconfig freetype gvc jng jpeg lcms lzma pangocairo png tiff x xml zlib
>
> # Create a postscript file we can work with:
> $ echo "Hello, World!" | paps --landscape --columns=80 --font "Monospace 20" > hello-world.ps
>
> # This output looks good, white background, black text:
> cat hello-world.ps| convert -density 128 -fill black -background white -flatten -rotate 90 -delete 0--2 - out.png
>
> # Though I'm getting this warning, is that the problem?:
> # convert: profile 'icc': 'RGB ': RGB color space not permitted on grayscale PNG `out.png' @ warning/png.c/MagickPNGWarningHandler/1667.
>
> # This produces only whiteness:
> # Same warning as above:
> cat hello-world.ps| convert -density 128 -fill black -background white -flatten -rotate 90 -delete 0--2 -negate - out-negated.png
>
> #But at least this works afterwards: White text on black background:
> convert out.png -negate outout.png
>
>
>
> Conclusion: As a quick workaround, you can add another pipe and use
> convert twice.
>
> But there should be a way to do it in one way. ImageMagick is a bit
> tricky in that. I have no idea for now.
>
> As reference, I'm attaching my output files.
>
> Björn
>

Re: Inverting command line session colours

[Ricardo Wurmus]

Björn Höfling <bjoern.hoefling@bjoernhoefling.de> writes:

> Conclusion: As a quick workaround, you can add another pipe and use
> convert twice.
>
> But there should be a way to do it in one way. ImageMagick is a bit
> tricky in that. I have no idea for now.

My guess is that it doesn’t work the first time around because the
background is in fact transparent.

I recommend not to waste time on this as colour management will be
overhauled eventually anyway.  With the use of Pango markup to specify
text colours you probably don’t want to invert the colours.

-- 
Ricardo

Re: Inverting command line session colours

[Laura Lazzati]

Hi!
Thank you Bruno for helping.
> Björn Höfling <bjoern.hoefling@bjoernhoefling.de> writes:
>
> > Conclusion: As a quick workaround, you can add another pipe and use
> > convert twice
I also tried with your example and made it work in my Makefile. BUT
the typography kind of changed Weird again, Stayed up late trying to
solve it.

> I recommend not to waste time on this as colour management will be
> overhauled eventually anyway.  With the use of Pango markup to specify
> text colours you probably don’t want to invert the colours.
Ok, great! Thank you, will switch to another task then :)

Regards :)
Laura