How to reduce an image size in image processing (scipy/numpy/python)

Hello I have an image ( 1024 x 1024) and I used "fromfile" command in numpy to put every pixel of that image into a matrix.

How can I reduce the size of the image ( ex. to 512 x 512) by modify that matrix a?

a = numpy.fromfile(( - path - ,'uint8').reshape((1024,1024))

I have no idea how to modify the matrix a to reduce the size of the image. So if somebody has any idea, please share your knowledge and I will be appreciated. Thanks

EDIT:

When I look at the result, I found that the reader I got read the image and put it into a "matrix". So I changed the "array" to matrix.

Jose told me I can take only even column and even row and put it into a new matrix . That will reduce the image to half size. What command in scipy/numpy do I need to use to do that?

Thanks