packing greyscale values

Peter Otten __peter__ at web.de
Mon Feb 11 11:11:25 CET 2008


jimgardener wrote:

> hi
> i am getting value of a pixel of a greyscale image using PIL's
> image.getdata and need to pack it as an int as below
> 
> ie greyvalues
> 127 , 56 , 135 , 99 , 102 , 101 , 146 , 112 , 155 , 154 , 112 , 169
> 
> should become
> -4473925, -8289919, -4144960, -5789785, -5592406, -5658199 ,-3684409,
> -5131855, -3289651,-3355444, -5131855, -2763307
> 
> (i got these values using java's BufferedImage class..)I would like to
> know if there is a way to do the conversion in python.(.i need 'these
> 'for some calculations)

Judging from

>>> hex(0x100000000 - 4473925)
'0xffbbbbbb'
>>> 0xbb
187

-4273925 indeed seems to denote a gray value, but the lighter 187 rather
than 127. Are you sure the lists you give belong to the same image?

Peter



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