[SciPy-user] step in arrays

Agustin Lobo scipy-user@scipy.net
Mon, 3 Feb 2003 16:02:56 +0100 (MET)


Thanks, 

why is it that, while

xplt.imagesc(b[0:2168:8,0:5004:8])
and
xplt.imagesc(b[0:2168:8,5004:0:-8])

display the image with a black background

xplt.imagesc(b[2168:0:-8,0:5004:8])

displays it with a green background?

(the background in the image
has value 128, so it seems that somehow I 
change the lut).

Agus

Dr. Agustin Lobo
Instituto de Ciencias de la Tierra (CSIC)
Lluis Sole Sabaris s/n
08028 Barcelona SPAIN
tel 34 93409 5410
fax 34 93411 0012
alobo@ija.csic.es


On 3 Feb 2003, bryan cole wrote:

> how about:
> 
> ...
> b.shape=(2168,5004)
> c = b[0:2168:8,0:5004:8] #this should subsample b every 8th point
> xplt.imagesc(c)
> ...
> 
> Bryan
> 
> On Mon, 2003-02-03 at 12:02, Agustin Lobo wrote:
> > Hi! 
> > I would need a little help on this:
> > 
> > I want to read a set of images
> > (raw bin data, unsigned int*8) and
> > display them using xply.imagesc just
> > to mae sure there have been no errors at downloding
> > them.
> > 
> > For each file, I'm doing the following:
> > 
> > f =open("NDVI_GIMMS_8KM.8107","r")
> > a=f.read()
> > b = array(a,typecode=UnsignedInt8)
> > b.shape = (2168,5004)
> > xplt.imagesc(b)
> > 
> > The problem is that, as the array "b" is very large,
> > the display takes too long. Therefore, I'm trying
> > to subsample b. I've tried with take(), but no luck.
> > The question is, how could I select every i.e. 10th row
> > and col from matrix b?
> > 
> > Also, any other comment on improving what I want to do
> > is welcome! (perhaps I can subsample at reading).
> > 
> > Thanks
> > 
> > Agus
> > 
> > 
> > Dr. Agustin Lobo
> > Instituto de Ciencias de la Tierra (CSIC)
> > Lluis Sole Sabaris s/n
> > 08028 Barcelona SPAIN
> > tel 34 93409 5410
> > fax 34 93411 0012
> > alobo@ija.csic.es
> > 
> > 
> > _______________________________________________
> > SciPy-user mailing list
> > SciPy-user@scipy.net
> > http://www.scipy.net/mailman/listinfo/scipy-user
> -- 
> Bryan Cole
> Teraview Ltd., 302-304 Cambridge Science Park, Milton Road, Cambridge CB4 0WG, United Kingdom.
> tel: +44 (1223) 435380 / 435386 (direct-dial) fax: +44 (1223) 435382
> 
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