The primary goal in this step is to suppress text symbols
in the document. The notion is to select pixels in the area
with relatively lower spatial frequency characteristics into the
layer FL. The spectral selection process removes the pixels in
regions contributing high spatial frequencies. The gray scale
image X of the input color document image I (of size N x M)
is used in the layer formation process because it consists of all
structural and textural details of an image. The gray component
is filtered first by a 2D Gaussian filter. The high pass filtered
image Y is: