| 摘要 |
PURPOSE:To obtain optimum gradation by executing the gradation conversion of image signals of red, green and blue in accordance with specific equations at the conversion of digital data obtained after the end of image processing into analog data. CONSTITUTION:When it is defined that the density of an image signal to be outputted at present is D, a gradation value after image processing is (n), the maximum value of the density signal D is Dmax, its minimum value is Dmin, and the maximum value of the gradation value is N, the density signal D is expressed by the equation D=(Dmax-Dmin)(n/N)<p>+Dmin-(1) (in the equation, P is the factor of conversion). The conversion characteristics shown in the drawings are obtained by simplifying the equation like D=Dmax(n/255). In this case, the number of gradations (gradation capacity) N is 256 stages (8 bits) and the density is assigned to all density areas in the gradation capacity of 256 stages. The characteristic curve shown in the drawings indicates the conversion factor p=3 and the change of density gradation is increased in the low density area, so that the gradation is appropriate to human's psychological evaluation. Thereby, an output image of high quality can be obtained by executing gradation conversion on the basis of the characteristics shown in the drawings.
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