Re: Inverting command line session colours

[Laura Lazzati <laura.lazzati.15@gmail.com>]

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
>