Re: [Matplotlib-users] Is really matplotlib this slooow for displaying images ? (sorry again)

[Eric E. <ems...@ob...>]

just to answer your question:

>You still haven't answered my question if you typically want grayscale
>or colormapped images ....
>  
>
I am using colourmaps.
Usually a 256 levels is usually more than enough! Here is what I did when
I transformed the midas lut and itt files (3 columns RGB in ascii files 
see below)
into local python lut (pglut for ppgplot lut).

I am now thinking of using another suggestion (from Arnd) on top of what 
you said.
If the image is very large then I only load the central region in imshow
(so I extract the central part, ''central'' meaning center with respect to
some predefined center, by default the centre of the image). Then if I want
to see the full image in the window I scale it (factor N)
by only plotting 1 out of N pixels.... This should reproduce what Midas 
did I think
(not so sure, but Midas has a timed display of < 0.2 sec there in fact 
whatever
the scale is / size of the window)

One note from a local neird: it seems that the normalisation (colour.py)
in the matplotlib 0.65 version
is doing a divide by (vmax - vmin) and this was timed to be quite long
(see previous mails...). But a numarray division should be instantaneous 
even
for such a big image so there is something wrong there. Maytbe first
do : dv = vmax - vmin and divide by dv? (maybe this is not the reason,
using ''divide" and '/' may be different too?)

Eric

"""######################################
   # MIDAS-LIKE LUT and ITT
   ######################################"""
class MidasLut:
    def __init__(self):
        self.LUT_PATH = '/soft/python/pcral/plotutils/midaslut/'
        self.R = arange(256)/255.
        self.G = arange(256)/255.
        self.B = arange(256)/255.
        self.L = arange(256)/255.
    def lut(self,name):   
        sname = str(name)
        sname = self.LUT_PATH+sname+".lasc"
	if os.path.isfile(sname):
           f = open(sname)
           list = f.readlines()
           for i in range(256):
             self.R[i] = float(list[i].split()[0])
             self.G[i] = float(list[i].split()[1])
             self.B[i] = float(list[i].split()[2])
           f.close
	else :
	   print 'ERROR: Lut file', name,'does not exist'
    def itt(name):  
        sname = str(name)
        sname = LUT_PATH+sname+".iasc"
	if os.path.isfile(sname):
           f = open(sname)
           list = f.readlines()
           for i in range(256):
             L[i] = float(list[i].split()[0])
           f.close
	else :
	   print 'ERROR: ITT file', name,'does not exist'

pglut = MidasLut()


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