invert colors in \externalfigure

invert colors in \externalfigure

[Pablo Rodriguez]

Dear list,

I have the following sample:

    \setuppapersize[A6]
    \setuplayout[width=middle]
    \starttext
    \startmakeup[standard][align=center]
    \dontleavehmode\externalfigure[cow][width=\textwidth]
    \stopmakeup
    \stoptext

How can I invert the colors in the external figure without having to
edit the image file?

Many thanks for your help,

Pablo
-- 
http://www.ousia.tk
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Re: invert colors in \externalfigure

[Wolfgang Schuster]

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> Pablo Rodriguez <mailto:oinos@gmx.es>
> 20. Januar 2016 um 13:10
> Dear list,
>
> I have the following sample:
>
> \setuppapersize[A6]
> \setuplayout[width=middle]
> \starttext
> \startmakeup[standard][align=center]
> \dontleavehmode\externalfigure[cow][width=\textwidth]
> \stopmakeup
> \stoptext
>
> How can I invert the colors in the external figure without having to
> edit the image file?
>
> Many thanks for your help,
You have to use the Adobe Reader to view the PDF.

\setupexternalfigure[location=default]

\starttext

\externalfigure[cow][width=\textwidth]

\startnegative
\externalfigure[cow][width=\textwidth]
\stopnegative

\startnegative
\externalfigure[cow][background=color,backgroundcolor=white,width=\textwidth]
\stopnegative

\stoptext

Wolfgang

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___________________________________________________________________________________

Re: invert colors in \externalfigure

[Marco Patzer]

> How can I invert the colors in the external figure without having
> to edit the image file?

Based on Peter Münster's grph-downsample.lua here some lines that
should get you started. Note that you'll need graphicsmagick (or
imagemagick for that matter. In the latter case change the call from
`gm convert` to `convert`). This will do the conversion on the fly.

\startluacode
  local format = string.format
  local function invert(oldname, newname)
    local s = format("gm convert -negate %s %s", oldname, newname)
    os.execute(s)
  end
  local formats = {"png", "jpg", "gif"}
  for _, s in ipairs(formats) do
    figures.converters[s] = figures.converters[s] or {}
    figures.converters[s]["invert." .. s] = invert
  end
\stopluacode

\setupexternalfigures [conversion=invert.jpg]
\setupexternalfigures [location=default]

\starttext
  \externalfigure[hacker]
\stoptext

Marco
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___________________________________________________________________________________

Re: invert colors in \externalfigure

[Pablo Rodriguez]

On 01/20/2016 01:19 PM, Wolfgang Schuster wrote:
>> Pablo Rodriguez 20. Januar 2016 um 13:10
>> [...]
>> How can I invert the colors in the external figure without having to
>> edit the image file?
>>
>> Many thanks for your help,
> You have to use the Adobe Reader to view the PDF.

Many thanks for your solution, Wolfgang.

I’m afraid that I’m on Linux and I don’t have Adobe Reader installed.

But it is fine for me, since I’m going to print the file with Adobe
Reader DC.

It seems that other viewers don’t implement the /TR entry from
/ExtGState dictionary (according to the PDF spec).

I’m going to report the issue for Ghostscript, mupdf and poppler, so
that they have the feature implemented.

Many thanks for your help,

Pablo


> \setupexternalfigure[location=default]
> 
> \starttext
> 
> \externalfigure[cow][width=\textwidth]
> 
> \startnegative
> \externalfigure[cow][width=\textwidth]
> \stopnegative
> 
> \startnegative
> \externalfigure[cow][background=color,backgroundcolor=white,width=\textwidth]
> \stopnegative
> 
> \stoptext
> 
> Wolfgang

-- 
http://www.ousia.tk
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___________________________________________________________________________________

Re: invert colors in \externalfigure

[Pablo Rodriguez]

On 01/20/2016 02:09 PM, Marco Patzer wrote:
>> How can I invert the colors in the external figure without having
>> to edit the image file?
> 
> Based on Peter Münster's grph-downsample.lua here some lines that
> should get you started. Note that you'll need graphicsmagick (or
> imagemagick for that matter. In the latter case change the call from
> `gm convert` to `convert`). This will do the conversion on the fly.

Many thanks for your reply, Marco.

I’m afraid it doesn’t work with PDF files. But it is fine for me, since
the solution provided by Wolfgang works fine.

Many thanks for your help,


Pablo
-- 
http://www.ousia.tk
___________________________________________________________________________________
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___________________________________________________________________________________

Re: invert colors in \externalfigure

[Alan BRASLAU]

On Wed, 20 Jan 2016 17:56:53 +0100
Pablo Rodriguez <oinos@gmx.es> wrote:

> On 01/20/2016 01:19 PM, Wolfgang Schuster wrote:
> >> Pablo Rodriguez 20. Januar 2016 um 13:10
> >> [...]
> >> How can I invert the colors in the external figure without having
> >> to edit the image file?
> >>
> >> Many thanks for your help,  
> > You have to use the Adobe Reader to view the PDF.  
> 
> I’m afraid that I’m on Linux and I don’t have Adobe Reader installed.

Not just on Linux... (Adobe reader is a notorious security hole).


With MetaFun, you can invert the colors using:

\startMPcode
  draw whatever... ;
  currentpicture := inverted currentpicture ;
\stopMPcode

Unfortunately, this does *not* work with externalfigure, i.e.
  \startMPcode
    draw externalfigure("cow") ;
    currentpicture := inverted currentpicture ;
  \stopMPcode
or
  \startMPcode
    draw rawtextext("\externalfigure [cow]") ;
    currentpicture := inverted currentpicture ;
  \stopMPcode
as inverted (a macro) operates on all the elements of the picture.

I find it easiest to use ImageMagick or gimp to invert the colors and
save this in a second image file.

Alan
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___________________________________________________________________________________

Re: invert colors in \externalfigure

[Pablo Rodriguez]

On 01/20/2016 07:35 PM, Alan BRASLAU wrote:
> On Wed, 20 Jan 2016 17:56:53 +0100 Pablo Rodriguez  wrote:
> 
>> On 01/20/2016 01:19 PM, Wolfgang Schuster wrote:
>>>> Pablo Rodriguez 20. Januar 2016 um 13:10
>>>> [...]
>>>> How can I invert the colors in the external figure without having
>>>> to edit the image file?
>>>>
>>>> Many thanks for your help,  
>>> You have to use the Adobe Reader to view the PDF.  
>>
>> I’m afraid that I’m on Linux and I don’t have Adobe Reader installed.
> 
> Not just on Linux... (Adobe reader is a notorious security hole).

Many thanks for your reply, Alan.

\startnegative is the way of doing it, as Wolfgang suggested. Don’t
worry, I won’t install Adobe Reader.

Ghostscript also implements what actually is the /TR (transformation)
entry for /ExtGState (graphics state) dictionary. (I was wrong in my
previous message.)

Only poppler and mupdf should implement it.

Many thanks for your help,

Pablo
-- 
http://www.ousia.tk
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
archive  : http://foundry.supelec.fr/projects/contextrev/
wiki     : http://contextgarden.net
___________________________________________________________________________________