[Qgis-community-team] compiling manual & image quality

[Jacolin Yves]

Le Friday 21 August 2009 16:01:19 Stephan Holl, vous avez écrit :
> Hello Jacolin,
>
> Jacolin Yves <yjacolin at free.fr>, [20090821 - 14:39:31]
>
> > Le Friday 21 August 2009 14:36:15 MORREALE Jean Roc, vous avez écrit :
> > > Otto Dassau a écrit :
> > > > On Fri, 21 Aug 2009 13:11:40 +0200
> > > >
> > > > MORREALE Jean Roc <jr.morreale at enoreth.net> wrote:
> > > >> Otto Dassau a écrit :
> > > >>> Hi Jean Roc,
> > > >>>
> > > >>> On Fri, 21 Aug 2009 11:04:10 +0200
> > > >>>
> > > >>> MORREALE Jean Roc <jr.morreale at enoreth.net> wrote:
> > > >>>> Hi,
> > > >>>>
> > > >>>> I've been compiling the french manual for 1.0 (using
> > > >>>> texlive2008) but the quality of the images is very low : the
> > > >>>> jpg figuring in the final pdf are full of compression blocks
> > > >>>> making some captures hard to read.
> > > >>>>
> > > >>>> All the source's images have been localized and saved as png
> > > >>>> (96dpi) so I would really like to have them show up in a
> > > >>>> better quality.
> > > >>>>
> > > >>>> What are the right options to change ?
> > > >>>
> > > >>> All images are simply converted during compilation without any
> > > >>> change of size or
> > > >>> resolution. In the english version, many figures are
> > > >>> screenshots with only 72dpi
> > > >>> resolution. You are right they sometimes could be better, but I
> > > >>> don't know of
> > > >>> any parameter for dvipdf or dvips conversion that make the
> > > >>> images look better,
> > > >>> except using images with a higher resolution - just my 2c.
> > > >>>
> > > >>> Regards,
> > > >>>  Otto
> > > >>
> > > >> Hi Otto,
> > > >>
> > > >> It is not a matter of size or resolution but of jpeg artifacts
> > > >> due to a drastic compression, when I compare the png/eps they do
> > > >> not show these blocks but the jpgs included in the pdf are full
> > > >> of it. I think  the quality setting used by convert is below
> > > >> 60%, if we could get it up to 75% the images would be less
> > > >> blocky and still around 5% of the size of the pngs
> > > >
> > > > Hi Jean Roc,
> > > >
> > > > ok, but since the pdf figures are created from eps format, I
> > > > wonder where we can improve the process since b) uses eps files
> > > > created in a):
> > > >
> > > > a) convert PNG and JPEG to EPS defined in the Makefiles
> > > > b) create a PDF with dvipdf (a combination of dvips and ps2pdf)
> > > > using EPS figures from a)
> > > >
> > > > and when I look at the branches/1.0.0/french/user_guide folder, I
> > > > don't see any jpeg images except the qgis logo on the front page,
> > > > or am I wrong?
> > > >
> > > > Can you give an example image where you think there is a big
> > > > quality problem?
> > > >
> > > > Regards,
> > > >  Otto
> > >
> > > For example take a look at startup1.0.0.png and the image as it
> > > appears in the pdf (here saved as a jpg but could have been
> > > exported as a tiff with the same defects), you can see color
> > > distorsion and noise which are typical of an heavy quantization
> > > step:
> > >
> > > http://uppix.net/5/e/6/4197c43cfb28e319c4889368f40cd.png
> > > http://uppix.net/d/a/b/83b44bd238113703618b279045a45.jpg
> >
> > Hello,
> >
> > After looking in Google, it seems that dvipdf is known as not be the
> > best way to create PDF file with nice picture. Some people advice to
> > use latex2pdf.
> >
> > Jean-Roc, could you test it this afternoon, or do you prefer Iet me
> > test to build to night ? :)
>
> I have very good experiences in using pdflatex which eates png, jpg,
> etc. and the quality is very good.
>
> One bonus would be getting rid of the (large) eps-files lurking arround.
> Though this task involves some reworking of the current Image-Handling
> inside all Makefiles.
>
> I am not very happy to make this major rework of the build process
> before an upcoming release of QGIS (and the manual) as well, but I am
> willing to provide input if you decide to do so.

Stephan,

let's try on the French release of the QGIS user guide :) and after testing we 
could discuss about change this in the trunk doc.

Are you ok about this?

Y.
-- 
Yves Jacolin

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