[Numpy-discussion] image to array doubt
devnew@gmai...
devnew@gmai...
Fri Feb 29 08:54:49 CST 2008
hi
i came across a codebase by rice univ people..in that there are some
functions for conversion btw image and vectors
1.<code>
def image_to_vector(self, filename):
try:
im = Image.open(filename)
except IOError:
print 'couldn\'t load ' + filename
sys.exit(1)
self.im_size = im.size
a = numpy.array(im.getdata())
return a - 128
</code>
what is the purpose of a-128 here? i couldn't quite understand
2.<code>
def vector_to_image(self, v, filename):
v.shape = (-1,)
a, b = min(v), max(v)
span = max(abs(b), abs(a))
im = Image.new('L', self.im_size)
im.putdata((v * 127. / span) + 128)
im.save(filename)
</code>
and why the calculations of a,b span? why do you need the extra maths
ops inside im.putdata() I couldn't quite follow it
can someone explain this?
thanks
D
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