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Re: st: Graph output: wmf to gif?


From   cnguyen@stata.com
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Graph output: wmf to gif?
Date   Wed, 02 Apr 2003 15:38:47 -0600

"David LB Schwappach" <dlb@h-ero.de> wrote:

> my original query has inspired an interesting discussion on the list. I
> agree with Lee Sieswerda and others, that eps is best for paper
> publication of graphs, such as journal submissions. However, as initial
> format for gif conversion for web publication, my experiences are not as
> good as reported by Lee. Through my eyes, the result are never as sharp
> and precise as wmf to gif converted graphs (this may be an issue

Actually, the opposite is true but you are correct about the sharpness.  EPS
is more precise than WMF and therein lies the problem.  EPS uses points as a
unit of measurement (which is 1/72 of an inch) and you can have fractional
points.  WMF and PICT use pixels as a unit of measurement with 72 pixels per
inch (in the ideal resolution) and of course pixel sizes are integers.

When you convert an EPS file to a bitmap, the EPS converter tries to maintain
the size of the line relative to the size of the image.  Because a pixel is
the smallest screen unit, it tries to fool the eye into thinking a line is
thin using antialasing and drawing it "lighter".  A solid black one pixel line
next to a light gray one pixel line appears "thicker" even though they're the
same pixel thickness.  The minimum line thickness in WMF is 1 pixel so smaller
images appear "sharper".

I do agree with David that his examples seem to show that WMF to GIF appears
to give better results.  However, the EPS image appears to be slightly
smaller, the font used seems to be wider (and thinner in stroke) giving less
room to the actual plot area.  You typically don't get the benefit of
antialiasing when using WMF (I pasted a graph into Photoshop and curves and
circles remained jagged).  I'd also like to point out that the last bar
actually shows up in the EPS graph whereas the WMF graph shows nothing.

Anyway, I still contend that EPS to gif is the better way to go as the results
at http://www.stata.com/stata8/graphics.html show but it requires the image be
large enough.  Any graph that contains more than just horizontal and vertical
lines as well as thick lines should look better.  Take a close look at
http://www.stata.com/stata8/g/twoarea.gif and
http://www.stata.com/stata8/g/g_linee.gif.

btw, you should be able to print a PDF file to a non-PostScript printer using
Acrobat Reader as a kind of a cheapy RIP (Raster Image Processor).  I used to
do that with that with a lot of our color PostScript files that I needed to
print on a color non-PostScript printer.  You can avoid paying the often
expensive PostScript option on many printers doing this.

-Chinh Nguyen
 cnguyen@stata.com
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