LyX 2.4.0 (IM policy.xml ban on eps/pdf conversions)

[Pavel Sanda]

On Mon, Jan 24, 2022 at 11:32:42PM +0100, Pavel Sanda wrote:
> On Thu, Dec 02, 2021 at 10:24:58PM +0100, Pavel Sanda wrote:
> > - improve detection/users warning for banned eps->* conversion of imagemagick (high priority before final release, but not for next alpha/beta etc)
> 
> One option to automatically overcome the issue is to disable eps->png conversion and allow pdf->png so that lyx performs eps->pdf->png.
> On my debian adding this to preferences sort of fixes the issue:
> 
> \converter "pdf6" "png" "pdftoppm -png -singlefile $$i >  $$o" ""
> \converter "eps" "png" "" ""
> 
> Problems I see:
> - the zoom factors in lyx window are not consistent with previous IM conversion (you need to remove cache to test this)

I found out that IM uses by default DPI of 72 when calling GS so this problem is solved by using "pdftoppm -r 72 -png -singlefile $$i >  $$o"
Transparency is lost but I don't think that is a big deal.

> - not sure how is the pdftoppm conversion portable to windows/mac environment

Actually we have GS under our control for Win, not sure about Mac but mayb the IM policy is not to ban eps/pdf conversions.

> We could perhaps check policy.xml of IM and add those only in case eps/pdf is banned when doing reconfigure.

Jose, could I ask for pythonic help?
We would need a routine in configure.py which check whether to remove eps->png conversion in case IM bans those conversions.
That could be done this way by checking return status of the conversion. In bash that would be something like this:

echo '%!PS' > /tmp/.lyx_configure_test.eps
convert  /tmp/.lyx_configure_test.eps /tmp/.lyx_configure_test.png
if ! [ $? == 0 ] ; then 
  # remove eps->png conversion from configure settings, i.e. set \converter "eps" "png" "" ""
fi


Completely different way would be mimicking what IM internally does with GS when converting eps->png. I already checked little bit and unfortunately it won't be oneliner if we want to get resolution right. But probably doable with additional script of our own.
Pavel