Gamma correction, image processing method and program, gamma correction circuit, image processing apparatus, and display apparatus

A gamma correction method, comprising:

• inputting, as an input signal, a signal of (N+M) bits comprising of a signal Tn of N-bits and a signal Tm of M bits and outputting a tone signal Tout of Y bits having a linear tone-luminance characteristic expressed as Tout=ATn×Tm with a constant A and with an index number of N bits indicated Tn and a mantissa of M bits indicated with Tm, thereby to effect format conversion;
• and
• inputting a value of Tout and outputting a tone signal Tin of X bits (X<Y) converted non-linearly in a tone-luminance characteristic, thereby to effect gamma correction process wherein
• A is a natural number power of 2,
• M satisfies the relationship of M≦Y−N,
• the minimum value of said N is 2 when A is 2 and 1 when A is larger than 2, and
• the maximum value of N determined on the basis of A and M is the maximum value resulting in that a set of the values of Tn and Tm becomes a set of different values for all values of Tin.

A gamma correction program controlling a computer to perform a gamma correction process comprising:

• inputting a value of a tone input signal Tin of X bits having non-linear tone-luminance characteristic and outputting a tone signal Tout of Y bits (X<Y) having a tone-luminance characteristic converted to a linear characteristic, thereby to effect inverse gamma correction;
• and
• inputting Tout and outputting a tone output signal of (N+M) bits formed of a set of Tn and Tm which is nearest to Tout when Tout is expressed as AˆTn×Tm with a constant A, an index number indicated by the signal Tn of N bits and a mantissa indicated by the signal Tm of M-bits, thereby to effect format conversion;
• wherein A is a natural number power of 2,
• M satisfies the relationship of M≦Y−N,
• the minimum value of N is 2 when A is 2 and 1 when A is larger than 2, and
• the maximum value of N which is determined on the basis of A and M is the maximum value resulting in that a set of the values of Tn and Tm becomes a set of different values for all values of Tin.

A gamma correction program controlling a computer to execute comprising:

• a format conversion process for inputting, as an input signal, the signal of (N+M) bits comprising of the signal Tn of N bits and the signal Tm of M bits and for outputting the tone signal Tout of Y bits having the linear tone-luminance characteristic expressed as Tout=ATn×Tm with a constant A and with an index number of N bits indicated said Tn and a mantissa of M bits indicated with said Tm;
• and
• a gamma correction process for inputting a value of said Tout and for outputting the tone signal Tin of X bits (X<Y) converted non-linearly in the tone-luminance characteristic,
• wherein a value of said constant A is a natural number power of 2,
• said M satisfies the relationship of M≦Y−N,
• the minimum value of said N is 2 when A is 2 and 1 when A is larger than 2, and
• the maximum value of said N determined on the basis of said constant A and said M is the maximum value resulting in that a set of the values of Tn and Tm becomes a set of different values for all values of Tin.

A gamma correction circuit comprising:

• circuitry for inputting a value of a tone input signal Tin of X bits having non-linear tone-luminance characteristic and for outputting a tone signal Tout of Y bits (X<Y) having the tone-luminance characteristic converted to the linear characteristic, thereby to effect inverse gamma correction;
• and
• circuitry for inputting said Tout and for outputting the tone output signal of (N+M) bits formed of a set of Tn and Tm which is nearest to said Tout when said Tout is expressed as ATn×Tm with a constant A, an index number indicated by the signal Tn of N bits and a mantissa indicated by the signal Tm of M bits, thereby to effect format conversion;
• wherein A is a natural number power of 2,
• M satisfies the relationship of M≦Y−N,
• the minimum value of N is 2 when A is 2 and 1 when A is larger than 2, and
• the maximum value of N which is determined on the basis of A and M is the maximum value resulting in that a set of the values of Tn and Tm becomes a set of different values for all values of Tin.

A gamma correction circuit comprising:

• a format conversion circuit for inputting, as an input signal, the signal of (N+M) bits comprising of the signal Tn of N bits and the signal Tm of M bits and for outputting the tone signal Tout of Y bits having the linear tone-luminance characteristic expressed as Tout=ATn×Tm with a constant A and with an index number of N bits indicated said Tn and a mantissa of M bits indicated with said Tm;
• and
• a gamma correction circuit for inputting a value of said Tout and for outputting the tone signal Tin of X bits (X<Y) converted non-linearly in the tone-luminance characteristic,
• wherein a value of said constant A is a natural number power of 2,
• said M satisfies the relationship of M≦Y−N,
• the minimum value of said N is 2 when A is 2 and 1 when A is larger than 2, and
• the maximum value of said N determined on the basis of said constant A and said M is the maximum value resulting in that a set of the values of Tn and Tm becomes a set of different values for all values of Tin.

An image processing apparatus for outputting an analog voltage to determine tone of a display apparatus, comprising:

• a DA converter for DA conversion of an input signal of M bits among the input signals comprising of the signal of N bits and the signal of M bits;
• and
• a reference voltage generator for outputting the reference voltage for DA conversion in said DA converter,
• wherein an index number Tn indicated with said signal of N bits and a mantissa Tm indicated with said signal of M bits are provided for expressing the tone signal Tout of Y bits having linear tone-luminance characteristic as Tout=ATn×Tm using a constant A,
• the value of said A is a natural number power of 2, and
• said reference voltage generator generates said reference voltage on the basis of said signal of N bits.