Patent ID: 7616212

Claim:
A data conversion method for a processor which refers to textures for converting an input value inputted to the processor into an output value by using a predetermined function, the processor executing: a first texture referring step for referring to a first texture and converting the input value into an unequal division value, the first texture being produced by dividing an input range by M pieces of data into (M−1) equal intervals and an output range by N pieces data into (N−1) equal intervals, where N is smaller than M, selecting N pieces of data in unequal division from the M pieces of data in the input range, and establishing correspondences between the selected N pieces of data and the N pieces of data in the output range; a second texture referring step for referring to a second texture and producing a linearly approximated component of the unequal division value, the second texture being produced by interpolating function values for each of the (N−1) intervals using zero degree and linear components of an orthogonal function expressing the function; a third texture referring step for referring to a third texture and producing an expansion coefficient corresponding to the unequal division value, the third texture being produced by interpolating texture groups having expansion coefficients of quadratic or larger degree components of the orthogonal function in each of the (N−1) intervals; a function value producing step for producing a function value of a quadratic or larger degree component of the orthogonal function for the interval containing the unequal division value; and an adding step for calculating the product of the expansion coefficient produced by the third texture referring step and the function value produced by the function value producing step, and adding the obtained product to the linearly approximated component produced by the second texture referring step to obtain the output value.