1. A method of processing an image in a diagnostic apparatus for diagnosing a disease using a captured image of an affected area, the method comprising: separating the captured image into a brightness component and a color information component; and extracting a region to be diagnosed based on the brightness component or the color information component of the captured image to highlight a likeness of the region, wherein in the extracting, a vascular region is extracted as a likelihood V from the captured image converted to a Lab color space, wherein the likelihood V is defined as: 
 V= 1−exp(( K.^ 2)/2*σ^2)) where K is defined as: 
 K =sqrt(λ1.*λ1+λ2.*λ2), σ is an adjustment coefficient; sqrt ( ) means a square root of each element; and λ1 and λ2 are real numbers indicating characteristic values of Hessian matrix for each pixel.