[Numpy-discussion] confusion about eigenvector
Peter Skomoroch
peter.skomoroch at gmail.com
Tue Mar 11 23:08:45 EDT 2008
I found this in my del.icio.us links, sorry I forgot to mention it at the
time:
http://www.owlnet.rice.edu/~elec301/Projects99/faces/code.html
All the best
On Thu, Mar 6, 2008 at 10:39 AM, devnew at gmail.com <devnew at gmail.com> wrote:
> ok..I coded everything again from scratch..looks like i was having a
> problem with matrix class
> when i used a matrix for facespace
> facespace=sortedeigenvectorsmatrix * adjustedfacematrix
> and trying to convert the row to an image (eigenface).
> by
> make_simple_image(facespace[x],"eigenimage_x.jpg",(imgwdth,imght))
> .i was getting black images instead of eigenface images.
>
> def make_simple_image(v, filename,imsize):
> v.shape=(-1,) #change to 1 dim array
> im = Image.new('L', imsize)
> im.putdata(v)
> im.save(filename)
>
>
> i made it an array instead of matrix
> make_simple_image(asarray(facespace[x]),"eigenimage_x.jpg",
> (imgwdth,imght))
> this produces eigenface images
>
> another observation,
> the eigenface images obtained are too dark,unlike the eigenface images
> generated by Arnar's code.so i examined the elements of the facespace
> row
>
> sample rows:
> [ -82.35294118, -82.88235294, -91.58823529 ,..., -66.47058824,
> -68.23529412, -60.76470588]
> ..
> [ 89.64705882 82.11764706 79.41176471 ..., 172.52941176
> 170.76470588 165.23529412]
>
> looks like these are signed ints..
>
> i used another make_image() function that converts the elements
> def make_image(v, filename,imsize):
> v.shape = (-1,) #change to 1 dim array
> a, b = v.min(), v.max()
> span = max(abs(b), abs(a))
> im = Image.new('L', imsize)
> im.putdata((v * 127. / span) + 128)
> im.save(filename)
>
> This function makes clearer images..i think the calculations convert
> the elements to unsigned 8-bit values (as pointed out by Robin in
> another posting..) ,i am wondering if there is a more direct way to
> get clearer pics out of the facespace row elements
>
>
>
>
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>
--
Peter N. Skomoroch
peter.skomoroch at gmail.com
http://www.datawrangling.com
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