\(ret = 
      Import["c:/zbs/html/content/vision/model/mathematic/Jesusface.bmp"]\)

Show[ret]

$ImportFormats

$ExportFormats

Shallow[InputForm[ret]]

retarray = ret[[1, 1] ];

Dimensions[retarray]

Export["c:/zbs/html/content/vision/model/mathematic/ganglion.txt", 
      retarray, "Table"]

MatrixQ[retarray]

se is the standard deviation for the excitatory portion of the gaussian in the 2D DOG.
si is the standard deviation for the inhibitory protion of the gausian the the 2D DOG

se  =  3

si  =  6

width is the radius of the receptive field in x and y (or i and j) .   It is sensitive to the size of the inhibitory region .   So currently these cells are all on center cells.

width  =  4*si

ganglion = 
        Table[(1/((se)*(Sqrt[2*Pi]))) 
                Exp[-((((((i - width))^2) + (((j - width))^2)))/((2*
                            (se^2))))] - (1/((si)*(Sqrt[2*Pi]))) 
                Exp[-((((((i - width))^2) + (((j - width))^2)))/((2*(((si))^2))))] // N, {i, 2*width + 1}, {j, 2*width + 1}];

Dimensions[ganglion]

Export["c:/zbs/html/content/vision/model/mathematic/cell.txt", 
      ganglion, "Table"]

Show[SurfaceGraphics[ganglion], 
      PlotRange -> {- .03,  .07}]

<< LinearAlgebra`MatrixManipulation`

subretarray = 
        SubMatrix[retarray, {1, 1}, {2*width + 1, 2*width + 1}];

Dimensions[subretarray]

Show[SurfaceGraphics[subretarray]]