Help with loading file into an array

[Jens Thoms Toerring]

peter berrett <pwberrett at gmail.com> wrote:
> I am trying to build a program that can find comets in a series of
> astronomical images. I have already written functions to find the comet in a
> series of images, the data of which is stored in embedded lists.

> The area I am having difficulty with is take a standard gif file (1024 x
> 1024) and reading it into an array or embedded lists.

> In a nutshell here is an example of what I want to do

> Let's say I have a gif file called 20130428_0000_c2_1024.gif in a folder
> called c:\comets

> I want to read the data from that gif file taking the red data (excluding
> the green and blue data) and store that in an array called Image[][] which
> is a nested array length 1024 with a list in each item of 1024 length (ie
> 1024 x 1024)

> Could someone please provide a piece of code to do the above so I can then
> go on to modify it to pick up different files from different folders? In
> particular I am keen to seen how you read in the data and also how you
> change the directory from which you are reading the image. >

the following should do the trick using, as Fábio already
suggested, the Python Image Library (PIL):

----------------8<-------------------------
#!/ur/bin/env python

import Image

im = Image.open( 'c:/comets/20130428_0000_c2_1024.gif' )
w, h = im.size
red_arr = [ ]
for y in range( h ) :
    red_line = [ ]
    for x in range( w ) :
        red_line.append( im.getpixel( ( x, y ) )[ 0 ] )
    red_arr.append( red_line )
----------------8<-------------------------

For obvious reasons I couldn't use 'Image' as the name of the list
of lists, so it's 'red_arr' instead. This is probably not the fas-
test solution, but it's simple and hopefully will get you started.

Concerning reading other files: here I may not understand your
problem since it looks rather trivial to me by simply passing
the open() method of 'Image' the name of a file in a different
directory.
                             Regards, Jens
-- 
  \   Jens Thoms Toerring  ___      jt at toerring.de
   \__________________________      http://toerring.de