Method and apparatus for converting gray scale in a digital data display device

Claim 3

A method as claimed in Claim 1 wherein the stage of creating said first table comprises: a step of selecting one of said M gray levels in the K-gray scale, a step of making "natural conversion" of said selected gray level to one in the N-gray scale for obtaining its gray scale value Vj, and a step of entering a check in the position of an index Vju using Vju = Vj as the initial value in said first table if no check has been entered in said position, letting Vju = Vju + 1 if a check has been entered in said position and entering a check in the position of the index Vju if Vju<N, and if Vju≧N, entering a check in the position of an index Vjd using Vjd = Vj - 1 as the initial value if no check has been entered in said position and letting Vjd = Vjd - 1 and entering a check in the position of the index Vjd if a check has been entered in said position.

Claim 4

A method as claimed in Claim 1 or 2 wherein the stage of creating said second table comprises: a step of selecting one of said M gray levels in the K-gray scale, a step of determining where the value Vin of said selected gray level is in the ascending order of M gray levels and determining its ranking J, a step of designating the J-th smallest index of the indices of the positions with a check entered in said second table as the Vout, and a step of entering said Vout into a position in said second table corresponding to said Vin.

Claim 5

Digital data display apparatus for converting selected M gray levels in a K-gray scale to an N-gray scale (where K>N≧M) comprising: a means for creating a first table in which each of said M gray levels is mapped in accordance with the order and magnitude of the relative brightness in the K-gray scale to different M gray levels in the N-gray scale, and a means for creating a second table in which the M gray levels in the N-gray scale mapped in said first table is mapped correspondingly to the M gray levels in said K-gray scale.

Claim 6

Digital data display apparatus for converting selected M gray levels in a K-gray scale to an N-gray scale (where K>N≧M) comprising: a means for creating a first table in which each of said M gray levels is mapped in accordance with the order and magnitude of the relative brightness in the K-gray scale to different M gray levels in the N-gray scale, and a means for creating a second table in which the M gray levels in the N-gray scale mapped in said first table is mapped correspondingly to the M gray levels in said K-gray scale.

Claim 7

An apparatus as claimed in Claim 4 wherein the means for creating said first table comprises: a means for selecting one of said M gray levels in the K-gray scale, a means for making "natural conversion" of said selected gray level to one in the N-gray scale and obtaining its gray scale value Vj, and a means for entering a check in the position of an index Vju using Vju = Vj as the initial value in said first table when no check has been entered in said position, letting Vju = Vju + 1 when a check has been entered in said position and entering a check in the position of the index Vju if Vju<N, and if Vju≧N, entering a check in the position of an index Vjd using Vjd = Vj - 1 as the initial value if no check has been entered in the position of the index Vjd and letting Vjd = Vjd - 1 and entering a check in the position of the index Vjd if a check has been entered in said position.

Claim 8

Apparatus as claimed in Claim 4 or 5 wherein the means for creating said second table comprises: a means for selecting one of said M gray levels in the K-gray scale, a means for determining where the value Vin of said selected gray level is in the ascending order of M gray levels in said M gray levels and determining its ranking J, a means for designating the J-th smallest index of the indices of the positions in which a check is entered in said second table as the Vout, and a means for entering said Vout into a position in said second table corresponding to said Vin.