Picture producing apparatus using picture information values correlated to light intensities in tonal conversion formula

Claim 1

A picture producing apparatus for producing a reproduced picture having middle tones on a recording sheet based on signals obtained by processing density information values of respective pixels of an original picture from a medium image of said picture recorded on a predetermined recording medium, said apparatus comprising a tone adjusting means for processing said density information and producing tonal intensity values by: (1) converting the density information values (D n values) of the respective pixels on the original picture, by using a density characteristic curve defining a relationship between density information values (D values) of the recording medium and picture information values (X values) correlated to incident light intensities from the original picture into the recording medium, into picture information values (X n values) correlated to the light intensities corresponding to the density information values (D n values) of the respective pixels; (2) converting the picture information values (X n values) correlated to said light intensities into tonal intensity values (y values) for tone adjustment by operating a tonal conversion formula: ##EQU10## where X: (X n -X H n), namely, a basic light intensity value obtained by substracting a picture information value (XHn) correlated to a light intensity of a brightest part of the original picture obtained via the density characteristic curve from a density information value (D H n) of a corresponding brightest part (H part) of the original picture, from a picture information value (Xn) correlated to a light intensity of a pixel obtained from a density information value (D n value) of a corresponding arbitrary pixel on the original picture by using the density characteristic curve; y: a tonal intensity value set for a pixel on the reproduced picture corresponding to the arbitrary pixel on the original picture; y H : a tonal intensity value set in advance for the brightest part (H part) of the original picture; y S : a tonal intensity value set in advance for a darkest part (S part) of the original picture; α: a surface reflectance of a recording sheet sheet on which the reproduced image is to be formed; β: a value determined by β=10 - γ ; ##EQU11## where X s n represents a picture information value (X s n) correlated to a light intensity of the corresponding darkest part obtained via the density characteristic curve from the density information value (D s n) of the darkest part (S) on the original picture; γ: an arbitrary coefficient.