| 摘要 |
PURPOSE:To relax a photographic condition of a variable density picture and an influence of a noise by making a weight factor for each density difference which is used whe the difference sum of density is calculated larger and larger as a picture element has larger and larger density or density gradient. CONSTITUTION:An input signal is quantized by a quantizer 20 and inputted to a counter 21 and a RAM22 to read storage contents in an address of the RAM22 which coincident with the density level, and the value obtained by adding one by a +1 circuit 23 is written in the same address. At the same time, the value of a counter 21 is written in the area of the RAM22 classified by density level, so appearance frequencies and picture element numbers classified by density level are obtained. Data on a reference variable density picture is stored in a ROM24 and a differece arithmetic part 25 refers to appearance frequencies to detemine the lowest density level. Picture element numbers are read out of the RAM22 in the order of the density level and correponsing density levels are read out of the readout ROM24 to calculate the density difference. This is summed up integrally by an adder 26 to calculate distances, which are compared with one another by a comparator 27 to discriminate a reference density picture having the shortest distance. |
