[poppler] (1) blurred text (2) ownership of TextBoxes

[Albert Astals Cid]

A Dimarts 21 Octubre 2008, Mark Summerfield va escriure:
> Hi,
>
> I recently started using the poppler library with the Qt4 headers and
> have found it easy to use and generally excellent.
> For example, see http://www.qtrac.eu/diffpdf.html
>
> (1)
>
> I'm now trying to develop a console app that will do 2-up, 4-up, and so
> on printing, optionally ignoring each page's margins to maximize the use
> of space.
>
> But unfortunately, I'm getting blurred pages and don't know why.
>
> I create a QPrinter in PDF mode and switch render hints _on_ for the
> poppler document which I render to a QImage. I then create a QPainter on
> the printer and switch its render hints _off_---so that it will just
> paint the QImage pixel for pixel.
>
> I've attached (the very rough first cut) of the source (since it is only
> 160 lines), in case anyone has the time/inclination to have a look, esp.
> since I'm hoping I just did something silly that you'll spot in a
> moment:-)
>
> [Another problem with the program is that poppler seems to default to 72
> dpi, but QPrinter depends on the actual printer driver, so in my case is
> 75 dpi.]

The problem with printing images that contain text is usually low resolution 
of the image, you should be able of fixing this asking for a huge image 
(setting a high xres and yres on renderToImage) that should give you 
acceptable printouts at cost of high memory usage. For example, the PS 
renderer when finds a image with transparency, that is not supported by PS, 
renders a image and puts it in the PS, the used DPI is 300, and some people 
still complain is too small.

>
> (2)
>
> In the docs it makes clear that you get ownership of Poppler::Document
> and Poppler::Page and so must delete them---that's fine, I use
> std::tr1::shared_ptr to handle that. But when you do
> Poppler::Page::textList() it isn't clear whether you get ownership of
> the Poppler::TextBoxes or not? I've assumed that you don't, but I'd like
> to know.

You assumed wrong, you need to take care of deleing the textboxes. I'll fix 
the documentation to clearly state that.

Albert

>
> Thanks!