Patent ID: 7983482

Claim:
A program stored on a non-transitory computer readable medium which enables the computer to function as a histogram approximate restoring unit for approximately restoring a pixel value histogram of an original image from image data (hereinafter, referred to as “compressed image data”) of a compressed image obtained by quantizing a pixel value of a pixel of data on the original image and run-length encoding the pixel value, comprising: discrete-histogram creating means that creates discrete histogram data by calculating a total L i (hereinafter, referred to as a “degree of pixel value”) of run lengths corresponding to a pixel value at the entire region or a specific partial region of the compressed image data from among a pixel value C i (i=1, 2, . . . , M; where M is a number of all pixel values included in the compressed image data) of the compressed image data stored in the compressed image storing means; and approximate-histogram creating means that creates approximate histogram data approximately expressing the appearance frequency of the pixel value of the original image data by distributing the degree L i of the pixel value of the discrete histogram data corresponding to the pixel value C i (i=1, 2, . . . , M) of the compressed image data to a degree L(x) of a pixel value x close to the pixel value C i so as to obtain a normal distribution having a standard deviation σ with the pixel value C i as center; wherein the approximate-histogram creating means creates the approximate histogram data by distributing a degree L i (i=1, 2, . . . , M) of the degree of pixel value of the discrete histogram data {(C i , L i )|i=1, 2, . . . , M} to a degree L(x) of the pixel value of a pixel value x approximate to the pixel value C so as to obtain a normal distribution expressed by a normal-distribution function G(x) in (Expression 1) G ⁡ ( x ) = L i 2 ⁢ π ⁢ σ ⁢ exp ⁡ ( - ( x - C i ) 2 2 ⁢ σ 2 ) . [ Expression ⁢ ⁢ 1 ]