A method for constructing a database having image information representing
a plurality of images including the steps of: a) calculating L.times.5
number of normalized edge histogram bins to generate L number of edge
histograms of a target image, wherein each edge histogram has five
normalized edge histogram bins and represents a spatial distribution of
five reference edges in a sub-image and L is a positive integer, wherein
the reference edges include four directional edges and a non-directional
edge; b) non-linearly quantizing the L.times.5 number of normalized edge
histogram bins to generate L.times.5 number of quantization index values
for the target image; c) storing the L.times.5 number of quantization
index values to the database; and d) repeating the steps a) to c) until
all of the stored images are processed to thereby construct the database
having the image information.