[Tutor] Numpy unexpected result: subtraction of cell values
Carnell, James E
jecarnell at saintfrancis.com
Mon Jan 11 19:20:50 CET 2010
I'm sure this is easy, but I am having a difficult time finding the
right search terms to find it on the Internet. Any help much
appreciated.
3 dimensional array(x,y,rgb) which is a PIL image into a numpy array
using 'asarray' function.
I want to subtract the Red Value in an array cell from a neighboring Red
Value cell.
>>> pictArray[39][4] #pixel at 39 4
array([150, 140, 120], dtype=unint8)
>>> pictArray[39][5] #pixel at 39 5
array([160, 150, 120], dtype=unint8)
>>> pictArray[39][4][0] #red pixel
150
>>> pictArray[39][5[0] #neighboring red pixel
160
>>> pictArray[39][4] - pictArray[39][5] )
246 # <--------------- ??? vs -10
How do I get the number -10? Does this have to do with the dtype?
Thanks in advance,
James Carnell
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