packing greyscale values

[jimgardener]

>>Are you sure the lists you give belong to the same image?

the greyvalues list was printed out by python script on a 3X4
sampleimage i made to check this

im=Image.open("mypicgrey.jpg")
pixels=im.getdata()
for pix in pixels:
   print pix

whereas the integers in the second list were from java code

FileInputStream fIn = new FileInputStream("mypicgrey.jpg");
JPEGImageDecoder jpeg_decode = JPEGCodec.createJPEGDecoder(fIn);
BufferedImage image = jpeg_decode.decodeAsBufferedImage();
int width = image.getWidth();
int height = image.getHeight();
int[] rgbdata = new int[width * height];
image.getRGB(0,0,width,height,rgbdata,0,width);

'rgbdata' now has the second list of integer values

if it was an rgb image with r,g,b values i could pack it as
return unpack("l", pack("BBBB", b, g, r, alpha))[0]
(where alpha=255)

but i don't know how to do this for a greyscale image
jim