How to get a 16bit Unsigned integer in python

Question

I currently read off pixels from an image using python PIL. These pixels are 16bit greyscale and are unsigned. However, whenever PIL reads them in it thinks they are signed and makes values that should be something like 45179 into -20357.

org_Image = Image.open(image)
org_Data = org_Image.load()
width, height = org_Image.size

    for y in range(0, height):
        temprow_data = []
        for x in range(0, width):
             temprow_data.append(org_Data[x, y])

How do I go about getting PIL to output unsigned instead of signed integers? Or is there a really easy way of taking the PIL input and converting it after?

User · Accepted Answer · 2013-10-23 16:46:00Z

8

Here is a solution with structs since I do not know how python represents negative numbers binarily.

import struct
struct.unpack('H', struct.pack('h', number))

It packs it as a short (2 bytes) and unpacks it as an unsigned short.

edited Oct 23, 2013 at 16:46

answered Oct 23, 2013 at 16:24

User

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2 Comments

Joran Beasley Over a year ago

good answer :) and maybe less of a sledgehammer than mine (you know something about when you have a hammer everything looks like a nail)

Zectbumo Over a year ago

you may want to mention this returns a tuple (number,)

Joran Beasley · Accepted Answer · 2013-10-23 16:21:08Z

3

>>> import numpy as np
>>> np.array([-20357],dtype="uint16")
array([45179], dtype=uint16)

in your case when you are done looping over everything and you have it in a list

just call np.array(my_list,dtype="uint16")

answered Oct 23, 2013 at 16:21

Joran Beasley

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