Re: Doc-view fonts

[Tim X]

Haines Brown <haines@HistoricalMaterialism.info> writes:

> Stefan, I've tried to find out about how Doc-view, xft and ghostscript
> are related in emacs PDF rendering, but without much luck.
>
> I understand that Emacs 23.2 uses xft by default to gain
> anti-aliasing. However, it seems that emacs' "display system" or
> doc-view mode are independent of xft or any anti-aliasing. I was unable
> to find out why anti-aliased fonts are not used to build the PNG image.
>
> Do emacs' "display system" and Doc-view mode refer to the same thing? 
> In any case, I can't take it very seriously:  
>
>   a) Because I'm viewing a PNG, I can't select text in it for
>   pasting. So is Doc-view mode merely for passive reading of a text? 
>
>   b) But apparently it is not for that either: the non-anti-aliased font
>   used to build the image of the text is very diffiult to read. So just
>   what is Doc-view mode for?
>
>   c) There is no message indicating that a PDF can't be displayed
>   because it is broken, but only a hang of the conversion process. 
>
>   d) As you point out, the search facility is of little use.  
>
> I have none of these problems when I do: "! xpdf file.pdf". Am I
> therefore to conclude that Doc-View is an experiment gone awry and that
> one ought not to use it? Or are all my difficulties because I'm not
> making proper use of Doc-view or have left something out that would make
> it useful?
>

Although I don't use doc-view mode myself, maybe I can clarify matters. 

The doc-view facility uses external programs to render images of the PDF
i.e. ghostscript and pdftotext (to get searchable content I expect). 

This means that if the quality is poor, most likely it is due to how
these external prorams are called and nothing to do with emacs or emacs
font rendering etc. 

If you do M-x customize-group <ret> doc-view <ret>

you will see a number of customize options that may improve the
situation. In particular you have

doc-view-resolution to set the DPI resolution of the output. I suspect
increasing this may address your problem

doc-view-ghostscript-options which you may be able to tweak to get
better output. 

I cannot address the selection issues. This may or may not be possible
(the fact you can search for text makes me think there may be a
mechanism to select as well - I thought there was a toggle which would
allow you to go from the rendered version to the text only version.

HTH

Tim


-- 
tcross (at) rapttech dot com dot au