Patent Document ID: 5524069
Application ID: 08351142
Patent Status: 1

Claim One:
1. A method of extracting a characteristic figure from a color picture, wherein the color picture is composed of the characteristic figure superimposed on a background area, said method comprising: (a) a step of scanning the color picture and electrically storing the scanned color picture as an array of pixels such that each pixel is represented by three color intensity values ##EQU21## where 0.ltoreq.R, G, B.ltoreq.1; (b) a step of converting the three color intensity values ##EQU22## of each pixel to corresponding three color density values ##EQU23## utilizing equations D.sub.r =-logR, D.sub.g =-logG, D.sub.b =-logB, thereby producing an original density picture; (c) a step of designating a pixel in the background area of the color picture and determining a reference density from the three color density values ##EQU24## ascertained for the designated pixel in said converting step; (d) a step of determining, for each pixel, a maximum value a.sub.max of a coefficient `a` in an equation ##EQU25## under a restriction where D.sub.r' .gtoreq.0, D.sub.g' .gtoreq.0, and D.sub.b' .gtoreq.0; (e) a step of selecting a value for a background elimination coefficient k.sub.1 in a range of 0&lt;k.sub.1 &lt;1; (f) a step of multiplying, for each respective pixel, k.sub.1 .multidot.a.sub.max with the reference density ascertained in said converting step for said respective pixel, thereby composing a background density picture composed of modified three color density values for each pixel; (g) a step of subtracting the modified three color density values of each pixel in the background density picture from the three color density values of a corresponding pixel in the original density picture, thereby producing a characteristic density picture composed of resultant three color density values ##EQU26## of each pixel; (h) a step of reverse-converting the resultant three color density values ##EQU27## of each pixel in the characteristic density picture to three color intensity values ##EQU28## utilizing equations R.sub.2 =10 Exp (-D.sub.r2), G.sub.2 =10 Exp (-D.sub.g2), B.sub.2 =10 Exp (-D.sub.b2); and (i) a step of displaying an image represented by the three color intensity values ##EQU29## of each pixel.