'**********************initmask() subroutine*************************
'
'   purpose: initialize the masks used by sobel() giving adjacent
'            pixels the appropriate "weight"
'
'   input: none
'
'   output: two matrices defining the weights to be used on adjacent
'           pixels when finding the sobel data
'
'   note: increasing the values in the masks will increase the
'           sensitivity of sobel...however, for the most part this
'           simply means more "noise" rather than better defined edges
'   also: the numbers have to stay relatively small because of the
'           sobel computations-->the bigger the multiplier in the matrix
'           the higher the results are on average, meaning more pixels
'           are black more often (hence the noise issue)
'
'********************************************************************
Sub initmask()
    '   -1  0   1
    '   -2  0   2
    '   -1  0   1
    xmask(1, 1) = -1
    xmask(1, 2) = 0
    xmask(1, 3) = 1
    xmask(2, 1) = -2
    xmask(2, 2) = 0
    xmask(2, 3) = 2
    xmask(3, 1) = -1
    xmask(3, 2) = 0
    xmask(3, 3) = 1
    
    '    1   2   1
    '    0   0   0
    '   -1  -2  -1
    ymask(1, 1) = 1
    ymask(1, 2) = 2
    ymask(1, 3) = 1
    ymask(2, 1) = 0
    ymask(2, 2) = 0
    ymask(2, 3) = 0
    ymask(3, 1) = -1
    ymask(3, 2) = -2
    ymask(3, 3) = -1
End Sub