packing greyscale values

[jimgardener]

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)

thanx
jim