[matplotlib-devel] PS, dpi, and imshow

2006-08-31 Thread Michael Fitzgerald

Hi all,

I have a question about the PS backend (building on the thread  
imshow with PS backend from ~ a month ago).  Evidently this backend  
is fixed at 72 dpi.  This isn't a problem with vector information.   
However, it would seem that one would want to use a higher resolution  
when plotting figures that use imshow() for raster data, since this  
command has several choices for interpolation.  As I understand, the  
AxesImage is sampled at this low-resolution when being written to PS/ 
EPS.  Subsequent interpolation is done when printing, or viewing with  
ghostview.  For the (originally?) raster data, gv seems to use a  
nearest-neighbor scheme, making the image blocky.  It would be nice  
to use matplotlib's interpolation instead.  Is there a fundamental  
reason this needs to be fixed at 72 dpi?  As some publishers ask for  
EPS files of e.g. 300 dpi, I would think it's theoretically possible  
to export at different resolutions.  My understanding is that the  
_preview_ image in the file is supposed to be 72 dpi.

One possible workaround is to scale up the size of the figure (in  
inches), but then fonts, line thickness, marker sizes, etc. must also  
be scaled, making it less-than-satisfactory.

Thank you in advance for any enlightenment, and please forgive my  
ignorance -- I must admit I don't know that much about PS, nor about  
the specific scheme used in matplotlib for getting the image data  
into the postscript file, so I may be critically mistaken in the  
above assessment.

Best,
Mike

(P.S. please cc me, as I'm not subscribed)





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Re: [matplotlib-devel] PS, dpi, and imshow

2006-08-31 Thread Darren Dale
I don't know how (or if) this can be improved, but I will gladly consider 
patches.


On Thursday 31 August 2006 03:09, Michael Fitzgerald wrote:
 Hi all,

 I have a question about the PS backend (building on the thread
 imshow with PS backend from ~ a month ago).  Evidently this backend
 is fixed at 72 dpi.  This isn't a problem with vector information.
 However, it would seem that one would want to use a higher resolution
 when plotting figures that use imshow() for raster data, since this
 command has several choices for interpolation.  As I understand, the
 AxesImage is sampled at this low-resolution when being written to PS/
 EPS.  Subsequent interpolation is done when printing, or viewing with
 ghostview.  For the (originally?) raster data, gv seems to use a
 nearest-neighbor scheme, making the image blocky.  It would be nice
 to use matplotlib's interpolation instead.  Is there a fundamental
 reason this needs to be fixed at 72 dpi?  As some publishers ask for
 EPS files of e.g. 300 dpi, I would think it's theoretically possible
 to export at different resolutions.  My understanding is that the
 _preview_ image in the file is supposed to be 72 dpi.

 One possible workaround is to scale up the size of the figure (in
 inches), but then fonts, line thickness, marker sizes, etc. must also
 be scaled, making it less-than-satisfactory.

 Thank you in advance for any enlightenment, and please forgive my
 ignorance -- I must admit I don't know that much about PS, nor about
 the specific scheme used in matplotlib for getting the image data
 into the postscript file, so I may be critically mistaken in the
 above assessment.

-
Using Tomcat but need to do more? Need to support web services, security?
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Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642
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