Color converting apparatus for performing a three-dimensional color conversion of a colored picture in a color space with a small capacity of memory

A color converting apparatus comprising:

• color converting data storing means for storing pieces of color converting data defined in an output color space, each of groups of eight pieces of color converting data Da, Db, Dc, Dd, De, Df, Dg and Dh among the color converting data being allocated at color converting addresses of eight lattice points Pa, Pb, Pc, Pd, Pe, Pf, Pg and Ph of one of rectangular parallelepipeds in that order which are formed by partitioning a lightness-color difference space in a lightness direction, a first color difference direction and a second color difference direction, each of the rectangular parallelepipeds being partitioned into a first triangular prism and a second triangular prism of which lateral edges are directed in the lightness direction, the first triangular Drism having the lattice points Pa, Pb, Pc placed at the same lightness in the lightness direction and the lattice points Pe, Pf and Pg placed at the same lightness in the lightness direction, the second triangular prism having the lattice points Pa, Pd, Pc placed at the same lightness in the lightness direction and the lattice points Pe, Ph and Pg placed at the same lightness in the lightness direction, and a block address of each of the rectangular parallelepipeds being represented by a color converting address of the lattice point Pa;
• input signal receiving means for receiving an input lightness signal Y, an input first color difference signal Cr and an input second color difference signal Cb, an input color defined in the lightness-color difference space being designated by the input signals Y, Cr and Cb, the input lightness signal Y being composed of an upper lightness signal UY and a lower lightness signal DY, the input first color difference signal Cr being composed of an upper first color difference signal UCr and a lower first color difference signal DCr, and the input second color difference signal Cb being composed of an upper second color difference signal UCb and a lower second color difference signal DCb;
• triangular prism selecting means for selecting either the first triangular prism or the second triangular prism with the lower first color difference signal DCr and the lower second color difference signal DCb received in the input signal receiving means and generating a triangular prism selecting signal indicating a triangular prism selected;
• address generating means for generating a selected block address with the upper lightness signal UY, the upper first color difference signal UCr and the upper second color difference signal UCb received in the input signal receiving means, a selected rectangular parallelepiped allocated at the selected block address being selected from among the rectangular parallelepipeds in the color converting data storing means, the input color being included in the selected rectangular parallelepiped defined in lightness-color difference space, a selected triangular prism of the selected rectangular parallelepiped being specified with the triangular prism selecting signal generated in the triangular prism selecting means, the input color being included in the selected triangular prism, and six color converting data Da, Db (or Dd), Dc, De, Df (or Dh) and Dg allocated at the color converting addresses of the lattice points Pa, Pb (or Pd), Pc, Pe, Pf (or Ph) and Pg of the selected triangular prism being read out from the color converting data storing means;
• and
• interpolation calculating means for interpolating output color coordinates defined in the output color space corresponding to input color coordinates designated by the input color in the lightness-color difference space as an output color value Do with the six color converting data Da, Db (or Dd), Dc, De, Df (or Dh) and Dg read out from the color converting data storing means under control of the address generating means while weighting the six color converting data Da, Db (or Dd), Dc, De, F, (or Dh) and Dg with the lower lightness signal DY and the lower first and second color difference signals DCr, DCb received in the input signal receiving means, a value DY1 of the lower lightness signal DY denoting a lightness component in the lightness direction of an input color vector directed from the lattice point Pa to the input color coordinates, a value DCr1 of the lower first color difference signal DCr denoting a first color difference component in the first color difference direction of the input color vector, a value DCb1 of the lower second color difference signal DCb denoting a second color difference component in the second color difference direction of the input color vector, and the interpolation calculating means comprising:
• difference generating means for calculating a first difference Db-Da, a second difference Dc-Db, a third difference De-Da, a fourth difference Df-De and a fifth difference Dg-Df between two of the color converting data Da to Dh in cases where the triangular prism selecting signal indicating the selection of the first triangular prism is received in the address generating means and calculating a sixth difference Dd-Da, a seventh difference Dc-Dd, an eighth difference De-Da, a ninth difference Dh-De and a tenth difference Dg-Dh between two of the color converting data Da to Dh in cases where the triangular prism selecting signal indicating the selection of the second triangular prism is received in the address generating means;
• first multiplying means for multiplying the first difference Db-Da, the second difference Dc-Db, the fourth difference Df-De and the fifth difference Dg-Df calculated in the difference generating means by the value DCr1 of the lower first color difference signal DCr or the value DCb1 of the lower second color difference signal DCb transferred from the input signal receiving means to obtain a first product DCr1*(Db-Da), a second product DCb1*(Dc-Db), a third product DCr1*(Df-De) and a fourth product DCb1*(Dg-Df) in cases where the triangular prism selecting signal indicating the selection of the first triangular prism is received in the address generating means and multiplying the seventh difference Dc-Dd, the sixth difference Dd-Da, the tenth difference Dg-Dh and the ninth difference Dh-De calculated in the difference generating means by the value DCr1 of the lower first color difference signal DCr or the value DCb1 of the lower second color difference signal DCb to obtain a fifth product DCr1*(Dc-Dd), a sixth product DCb1*(Dd-Da), a seventh product DCr1*(Dg-Dh) and an eighth product DCb1*(Dh-De) in cases where the triangular prism selecting signal indicating the selection of the second triangular prism is received in the address generating means;
• first adding means for adding the first product DCr1*(Db-Da) and the second product DCb1*(Dc-Db) produced in the first multiplying means to obtain a first added product DCr1*(Db-Da)+DCb1*(Dc-Db), adding the third product DCr1*(Df-De) and the fourth product DCb1*(Dg-Df) produced in the first multiplying means to obtain a second added product DCr1*(Df-De)+DCb1*(Dg-Df), adding the fifth product DCr1*(Dc-Dd) and the sixth product DCb1*(Dd-Da) produced in the first multiplying means to obtain a third added product DCr1*(Dc-Dd)+DCb1*(Dd-Da), and adding the seventh product DCr1*(Dg-Dh) and the eighth product DCb1*(Dh-De) produced in the first multiplying means to obtain a fourth added product DCr1*(Dg-Dh)+DCb1*(Dh-De);
• second adding means for adding the first added product DCr1*(Db-Da)+DCb1*(Dc-Db) produced in the first adding means and the color converting data Da transferred from the input signal receiving means to produce a first term product Da+DCr1*(Db-Da)+DCb1*(Dc-Db) in cases where the triangular prism selecting signal indicating the selection of the first triangular prism is received in the address generating means and adding the third added product DCr1*(Dc-Dd)+DCb1*(Dd-Da) produced in the first adding means and the color converting data Da to produce another first term product Da+DCr1*(Dc-Dd)+DCb1*(Dd-Da) in cases where the triangular prism selecting signal indicating the selection of the second triangular prism is received in the address generating means;
• subtracting means for subtracting the first added product DCr1*(Db-Da)+DCb1*(Dc-Db) from the second added product DCr1*(Df-De)+DCb1*(Dg-Df) produced in the first adding means to obtain first subtracted product DCr1*(Df-De)+DCb1*(Dg-Df)-DCr1*(Db-Da)-DCb1*(Dc-Db) and subtracting the third added product DCr1*(Dc-Dd)+DCb1*(Dd-Da) from the fourth added product DCr1*(Dg-Dh)+DCb1*(Dh-De) produced in the first adding means to obtain a second subtracted product DCr1*(Dg-Dh)+DCb1*(Dh-De)-DCr1*(Dc-Dd)-DCb1*(Dd-Da);
• third adding means for adding the first subtracted product DCr1*(Df-De)+DCb1*(Dg-Df)-DCr1*(Dd-Da)-DCb1*(Dc-Db) produced in the subtracting means and the third difference De-Da calculated in the difference generating means to produce a fifth added product De-Da+DCr1*(Df-De)+DCb1*(Dg-Df)-DCr1*(Db-Da)-DCb1*(Dc-Db) and adding the second subtracted product DCr1*(Dg-Dh)+DCb1*(Dh-De)-DCr1*(Dc-Dd)-DCb1*(Dd-Da) produced in the subtracting means and the third difference De-Da to produce a sixth added product De-Da+DCr1*(Dg-Dh)+DCb1*(Dh-De)-DCr1*(Dc-Dd)-DCb1*(Dd-Da);
• second multiplying means for multiplying the fifth added product De-Da+DCr1*(Df-De)+DCb1*(Dg-Df)-DCr1*(Db-Da)- DCb1*(Dc-Db) and the sixth added product De-Da+DCr1*(Dg-Dh)+DCb1*(Dh-De)-DCr1*(Dc-Dd)-DCb1*(Dd-Da) produced in the third adding means by the value DY1 of the lower lightness signal DY to obtain a second term product DY1*{De-Da+DCr1*(Df-De)+DCb1*(Dg-Df)-DCr1*(Db-Da)-DCb1*(Dc-Db)} in cases where the triangular prism selecting signal indicating the selection of the first triangular prism is received in the address generating means and another second term product DY1*{De-Da+DCr1*(Dg-Dh)+DCb1*(Dh-De)-DCr1*(Dc-Dd)-DCb1*(Dd-Da)} in cases where the triangular prism selecting signal indicating the selection of the second triangular prism is received in the address generating means;
• and
• fourth adding means for adding the first term product Da+DCr1*(Db-Da)+DCb1*(Dc-Db) produced in the second adding means and the second term product DY1*{De-Da+DCr1*(Df-De)+DCb1*(Dg-Df)-DCr1*(Db-Da)-DCb1*(Dc-Db)} produced in the second multiplying means to obtain the output color value Do=Da+DCr1*(Db-Da)+DCb1*(Dc-Db)+DY1*{De-Da+DCr1*(Df-De)+DCb1*(Dg-Df)-DCr1* (Db-Da)-DCb1*(Dc-Db)} in cases where the triangular prism selecting signal indicating the selection of the first triangular prism is received in the address generating means and adding the first term product Da+DCr1*(Dc-Dd)+DCb1*(Dd-Da) produced in the second adding means and the second term product DY1*{De-Da+DCr1*(Dg-Dh)+DCb1*(Dh-De)- DCr1*(Dc-Dd)-DCb1*(Dd-Da)} to obtain the output color value Do=Da+DCr1*(Dc-Dd)+DCb1*(Dd-Da)+DY1*{De-Da+DCr1*(Dg-Dh)+DCb1*(Dh-De)-DCr1* (Dc-Dd)-DCb1*(Dd-Da)} in cases where the triangular prism selecting signal indicating the selection of the second triangular prism is received in the address generating means produced in the second multiplying means.

A color converting apparatus comprising:

• color converting data storing means for storing pieces of color converting data defined in an output color space, a plurality of rectangular parallelepipeds being formed in a lightness-color difference space by partitioning the lightness-color difference space in a lightness direction, a first color difference direction and a second color difference direction, each of the rectangular parallelepipeds having four lattice points P1, P2, P3 and P4 placed at a first lightness in the lightness direction and other four lattice points P5, P6, P7 and P8 placed at a second lightness in the lightness direction, a block address (i,j,k) of each of the rectangular parallelepipeds being represented by a color converting address of the lattice point P1, and the color converting data being limitedly allocated at color converting addresses of the lattice points P1 to P8 of the rectangular parallelepipeds, of which the block addresses are respectively expressed by coordinates (2i, 2j, 2k) composed of three even numbers 2i,2j and 2k, to store the color converting data without any overlapping storage of the color converting data;
• lightness and color difference generating means for generating a lightness signal Y, a first color difference signal Cr and a second color difference signal Cb defined in a lightness-color difference space from a first primary color signal, a second primary signal and a third primary signal defined in a primary color space, an input color defined in the primary color space being designated by the first, second and third primary color signals, the input color defined in the lightness-color difference space being designated by the signals Y, Cr and Cb, the lightness signal Y being composed of an upper lightness signal YH having a value YH1 and a lower lightness signal DY having a value DY1, the first color difference signal Cr being composed of an upper first color difference signal CrH having a value CrH1 and a lower first color difference signal DCr having a value DCr1, and the second color difference signal Cb being composed of an upper second color difference signal CbH having a value CbH1 and a lower second color difference signal DCb having a value DCb1;
• first address generating means for generating a selected block address (YH1', CrH1', CbH1') of a selected rectangular parallelepiped represented by a color converting address (YH1', CrH1', CbH1') of a lattice point P1 of the selected rectangular parallelepiped with the upper lightness signal YH, the upper first color difference signal CrH and the upper second color difference signal CbH generated in the lightness and color difference generating means to specify the selected rectangular parallelepiped, a value YH1' of the selected block address (YH1', CrH1', CbH1') of the selected rectangular parallelepiped being equal to the value YH1 of the upper lightness signal YH, a value CrH1' of the selected block address (YH1', CrH1', CbH1') being equal to a sum of the value YH1, the value CrH1 of the upper first color difference signal CrH and a constant, a value CbH1' of the selected block address (YH1', CrH1', CbH1' being equal to a sum of the value YH1, the value CbH1 of the upper second color difference signal CbH and the constant,
• second address generating means having four first slid address generating elements and four second slid address generating elements for generating eight block addresses of eight particular rectangular parallelepipeds, which each have one of eight selected lattice points agreeing with eight lattice points Pa, Pb, Pc, Pd, Pe, Pf, Pg and Ph of a parallelepiped PP, with the selected block address (YH1', CrH1', CbH1') generated in the first address generating means, four block addresses of the eight block addresses being generated by incrementing the values CrH1' and CbH1' of the selected block address (YH1', CrH1', CbH1') in the first slid address generating elements in case where the value YH1' is an odd number, other four block addresses of the eight block addresses being generated by incrementing the values CrH1' and CbH1' of the selected block address (YH1', CrH1', CbH1') in the second slid address generating elements in case where the value YH1' is an even number, the input color being included in the parallelepiped PP having a first plane placed at a lightness in the lightness direction and a second plane parallel to the first plane, the first plane of the parallelepiped PP having the four lattice points Pa, Pb, Pc and Pd addressed at color converting addresses (Y.sub.o, Cr.sub.o, Cb.sub.o), (Y.sub.o, Cr.sub.o +1, Cb.sub.o), (Y.sub.o, Cr.sub.o +1, Cb.sub.o +1) and (Y.sub.o, Cr.sub.o, Cb.sub.o +1) in that order in a (YH', CrH', CbH') space, the second plane of the parallelepiped PP having the four lattice points Pe, Pf, Pg and Ph addressed at color converting addresses (Y.sub.o, +1, Cr.sub.o +1, Cb.sub.o +1), (Y.sub.o,+1, Cr.sub.o +2, Cb.sub.o +1), (Y.sub.o +1, Cr.sub.o +2, Cb.sub.o +2) and (Y.sub.o +1, Cr.sub.o +1, Cb.sub.o +2) in that order in the (YH', CrH', CbH') space, the color converting address (YH1', CrH1', CbH1') of the lattice point P1 of the selected rectangular parallelepiped agreeing with the color converting address (Y.sub.o, Cr.sub.o, Cb.sub.o) of the lattice point Pa or the color converting address (Y.sub.o +1, Cr.sub.o +1, Cb.sub.o +1) of the lattice point Pe in dependence on whether the value YH1' is an even number or an odd number, and the parallelepiped PP being formed of a first triangular prism with the lattice points Pa, Pb, Pc, Pe, Pf and Pg and a second triangular prism with the lattice points Pa, Pd, Pc, Pe, Ph and Pg, four pieces of color converting data M0, M1, M2 and M3 allocated at the color converting addresses of the selected lattice points agreeing with the lattice points Pa to Pd of the parallelepiped PP and other four pieces of color converting data M4, M5, M6 and M7 allocated at the color converting addresses of the selected lattice points agreeing with the lattice points Pe to Ph of the parallelepiped PP being read out from the color converting data storing means;
• triangular prism selecting means for selecting either the first triangular prism or the second triangular prism of the parallelepiped PP, of which the lattice point Pa agrees with the lattice point P1 of the selected rectangular parallelepiped specified in the first address generating means, with the lower first color difference signal DCr and the lower second color difference signal DCb generated in the lightness and color difference generating means and generating a triangular prism selecting signal indicating a triangular prism selected;
• first selecting means for selecting three pieces of color converting data from among the color converting data M0 to M3 as three pieces of color converting data Da, Db (or Dd) and Dc allocated at the color converting addresses of the lattice points Pa, Pb (or Pd) and Pc of the first or second triangular prism of the parallelepiped PP in that order according to the triangular prism selecting signal generated in the triangular prism selecting means and the selected block address (YH1', CrH1', CbH1') generated in the first address generating means;
• second selecting means for selecting three pieces of color converting data from among the color converting data M4 to M7 as three pieces of color converting data De, Df (or Dh) and Dg allocated at the color converting addresses of the lattice points Pe, Pf (or Ph) and Pg of the first or second triangular prism of the parallelepiped PP in that order according to the triangular prism selecting signal generated in the triangular prism selecting means and the selected block address (YH1', CrH1', CbH1') generated in the first address generating means;
• weight controlling means for controlling the value DY1 of the lower lightness signal DY generated in the lightness and color difference generating means to convert the value DY1 to a controlled value 1-DY1 in cases where the value YH1 of the upper lightness signal YH generated in the lightness and color difference generating means is an odd number, the value DY1 being expressed by a symbol DY1' in cases where the value YH1 is an even number, and the controlled value 1-DY1 being expressed by the same symbol DY1' in cases where the value YH1 is an odd number;
• and
• interpolation calculating means for interpolating coordinates of an output color defined in the output color space corresponding to input color coordinates of the input color as an output color value Do in the first or second triangular prism of the parallelepiped PP with the six color converting data Da, Db (or Dd), Dc, De, Df (or Dh) and Dg selected in the first selecting means and the second selecting means while weighting the six color converting data with the values DCR1 and DCb1 of the lower signals DCr and DCb generated in the lightness and color difference generating means and the value DY1' of the lower lightness signal DY defined by the weight controlling means, the value DY1' of the lower lightness signal DY denoting a lightness component in the lightness direction of an input color vector directed from the lattice point Pa to the input color coordinates, the value DCr1 of the lower first color difference signal DCr denoting a first color difference component in the first color difference direction of the input color vector, and the value DCb1 of the lower second color difference signal DCb denoting a second color difference component in the second color difference direction of the input color vector.

A color converting apparatus comprising:

• color converting data storing means for storing six types of pieces of color converting data M0 to M5 defined in an output color space, a plurality of rectangular parallelepipeds being formed in a lightness-color difference space by partitioning the lightness-color difference space in a lightness direction, a first color difference direction and a second color difference direction, each of the rectangular parallelepipeds having four lattice points P1, P2, P3 and P4 at a first block plane placed at a color difference plane of the lightness-color difference space and other four lattice points P5, P6, P7 and P8 at a second block plane placed at another color difference plane of the lightness-color difference space, a block address of each of the rectangular parallelepipeds being represented by a color converting address of the lattice point P1, the color converting data M0 to M2 being allocated at color converting addresses of the lattice points P1 to P4 of the rectangular parallelepipeds to repeatedly arrange the color converting data M0 to M2 in the first color difference direction and the second color difference direction in that order, and the color converting data M3 to M5 being allocated at color converting addresses of the lattice points P5 to P8 of the rectangular parallelepipeds to repeatedly arrange the color converting data M3 to M5 in the first color difference direction and the second color difference direction in that order;
• lightness and color difference generating means for generating a lightness signal Y, a first color difference signal Cr and a second color difference signal Cb defined in a lightness-color difference space from a first primary color signal, a second primary signal and a third primary signal defined in a primary color space, an input color defined in the primary color space being designated by the first, second and third primary color signals, the input color defined in the lightness-color difference space being designated by the signals Y, Cr and Cb, the lightness signal Y being composed of an upper lightness signal YH having a value YH1 and a lower lightness signal DY having a value DY1, the first color difference signal Cr being composed of an upper first color difference signal CrH having a value CrH1 and a lower first color difference signal DCr having a value DCr1, and the second color difference signal Cb being composed of an upper second color difference signal CbH having a value CbH1 and a lower second color difference signal DCb having a value DCb1;
• first address generating means for generating a selected block address (YH1', CrH1', CbH1') of a selected rectangular parallelepiped represented by a color converting address (YH1', CrH1', CbH1') of a lattice point P1 of the selected rectangular parallelepiped with the upper lightness signal YH, the upper first color difference signal CrH and the upper second color difference signal CbH generated in the lightness and color difference generating means to specify the selected rectangular parallelepiped, the input color being included in a parallelepiped PP having a first plane placed at a lightness in the lightness direction and a second plane parallel to the first plane, the first plane of the parallelepiped PP having four lattice points Pa, Pb, Pc and Pd addressed at color converting addresses (Y.sub.o, Cr.sub.o, Cb.sub.o), (Y.sub.o, Cr.sub.o +1, Cb.sub.o), Y.sub.o, Cr.sub.o +1, Cb.sub.o +1) and (Y.sub.o, Cr.sub.o, Cb.sub.o +1) in that order, the second plane of the parallelepiped PP having four lattice points Pe, Pf, Pg and Ph addressed at color converting addresses (Y.sub.o +1, Cr.sub.o +1, Cb.sub.o +1), (Y.sub.o +1, Cr.sub.o +2, Cb.sub.o +1), (Y.sub.o +1, Cr.sub.o +2, Cb.sub.o +2) and (Y.sub.o +1, Cr.sub.o +1, Cb.sub.o +2) in that order, the color converting address (YH1', CrH1', CbH1') of the lattice point P1 of the selected rectangular parallelepiped agreeing with the color converting address (Y.sub.o, Cr.sub.o, Cb.sub.o) of the lattice point Pa or the color converting address ((Y.sub.o +1, Cr.sub.o +1, Cb.sub.o +1) of the lattice point Pe in dependence on whether the value YH1' is an even number or an odd number, and the parallelepiped PP being formed of a first triangular prism with the lattice points Pa, Pb, Pc, Pe, Pf and Tg and a second triangular prism with the lattice points (Pa, Pd, Pc, Pe, Ph and Pg;
• second address generating means for generating a memory address CrH" in the first color difference direction, a memory address CbH" in the second color difference direction, a CrH" remainder Tx and a CbH" remainder Ty with the selected block address (YH1', CrH1', CbH1') of the selected rectangular parallelepiped, the memory address CrH" being a quotient obtained by dividing a first slid value CrH1S' by 3, the memory address CbH" being equal to a second slid value CbH1S', the CrH" remainder Tx being a remainder obtained by dividing the first slid value CrH1S' by 3, the CbH" remainder Ty being a remainder obtained by dividing the second slid value CbH1S' by 3, the first and second slid value CrH1S', CbH1S' being obtained by incrementing the values CrH1', CbH1' to determine color converting addresses of the color converting data M0 to M2 in cases where the value YH1' is an even number, the first and second slid value CrH1S', CbH1S' being obtained by incrementing the values CrH1', CbH1' to determine color converting addresses of the color converting data M3 to M5 in cases where the value YH1' is an odd number, and the first and second slid value CrH1S', CbH1S' being equal to the values CrH1', CbH1' in other cases;
• triangular prism selecting means for selecting either the first triangular prism or the second triangular prism of the parallelepiped PP of which the lattice point Pa agrees with) the lattice point P1 of the selected rectangular parallelepiped specified in the first address generating means with the lower first color difference signal DCr and the lower second color difference signal DCb generated in the lightness and color difference generating means;
• third address generating means for generating six color converting addresses of the lattice points Pa, Pb (or Pd), Pc, Pe, Pf (or Ph) and Pg of a particular triangular prism selected in the triangular prism selecting means with the memory address CrH"', ChH", YH" an the remainders Tx, Ty generated in the second address generating means, the color converting data M0 to M5 allocated at the color converting addresses of the lattice points Pa, Pb (or Pd), Pc, Pe, Pf (or Ph) and Pg of the particular triangular prism being read out from the color converting data storing means;
• first selecting means for selecting three pieces of color converting data Da, Db (or Dd) and Dc allocated at the color converting addresses of the lattice points Pa, Pb (or Pd) and Pc in that order from the color converting data M0 to M2 read out from the color converting data storing means;
• second selecting means for selecting three pieces of color converting data De, Df (or Dh) and Dg allocated at the color converting addresses of the lattice points Pe, Pf (or Ph) and Pg in that order from the color converting data M3 to M5 read out from the color converting data storing means;
• weight controlling means for controlling the value DY1 of the lower lightness signal DY generated in the lightness and color difference generating means to convert the value DY1 to a controlled value 1-DY1 in cases where the value YH1 of the upper, lightness signal YH generated in the lightness and color difference gengrating means is an odd number, the value DY1 being expressed by a symbol DY1' in cases where the value YH1 is an even number, and the controlled value 1-DY1 being expressed by the same symbol DY1' in cases where the value YH1 is an odd number;
• and
• interpolation calculating means for interpolating coordinates of an output color defined in the output color space corresponding to input color coordinates of the input color as an output color value Do in the particular triangular prism with the six color converting data Da, Db (or Dd), Dc, De, Df (or Dh) and Dg selected in the first selecting means and the second selecting means while weighting the six color converting data with the values DCr1 and DCb1 of the lower signals DCr and DCb generated in the lightness and color difference generating means and the value DY1' of the lower lightness signal DY defined by the weight controlling means, the value DYI' of the lower lightness signal DY denoting a lightness component in the lightness direction of an input color vector directed from the lattice point Pa to the input color coordinates, the value DCr1 of the lower first color difference signal DCr denoting a first color difference component in the first color difference direction of the input color vector, and the value DCb1 of the lower second color difference signal DCb denoting a second color difference component in the second color difference direction of the input color vector.

A color converting apparatus, comprising:

• color converting data storing means for storing pieces of color converting data defined in an output color space, a plurality of rectangular parallelepipeds being formed in a primary color space by partitioning the primary color space in a first primary color direction, a second primary color direction and a third primary color direction, each of the rectangular parallelepipeds having four lattice points P1, P2, P3 and P4 placed at a first-second primary color plane of the primary color space and other four lattice points P5, P6, P7 and P8 placed at another first-second primary color plane of the primary color space, a block address (i, j, k) of each of the rectangular parallelepipeds being represented by a color converting address of the lattice point P1, and the color converting data being limitedly allocated at the color converting addresses of the lattice points P1 to P8 of the rectangular parallelepipeds, of which the block addresses are respectively expressed by coordinates (2i, 2j, 2k) composed of three even numbers 2i, 2j and 2k, to store the color converting data without any overlapping storage of the color converting data;
• primary color signal dividing means for dividing a first primary color signal into an upper first color signal having a value RH1 and a lower first color signal having a value RL1, a second primary color signal into an upper second color signal having a value BH1 and a lower second color signal having a value BL1, and a third primary color signal into an upper third color signal having a value GH1 and a lower third color signal having a value GL1, the first, second and third primary color signals being defined in the primary color space and designating an input color;
• lower color signal comparing means for comparing the values RL1, GLI of the lower first and third color signals divided in the primary color signal dividing means to output a first compared result in dependence on a large and small relationship between the values RL1, GLI and comparing the values BL1, GL1 of the lower second and third color signals divided in the primary color signal dividing means to output a second compared result in dependence on a large and small relationship between the values BL1, GL1;
• adding means for adding the first compared result produced in the lower color signal comparing means to the value RH1 of the upper first color signal divided in the primary color signal dividing means to produce a first component having a value RH1', adding the second compared result produced in the lower color signal comparing means to the value BH1 of the upper second color signal divided in the primary color signal dividing means to produce a second component having a value BH1', and producing a third component having a value GH1' which is the same as the value GH of the upper third color signal divided in the primary color signal dividing means, a selected block address (RH1', BH1', GH1') of a selected rectangular parallelepiped being specified, the input color being included in a parallelepiped PP having a first plane placed at a primary color value G.sub.o in the third primary color direction and a second plane parallel to the first plane, the first plane of the parallelepiped PP having four lattice points Pa, Pb, Pc and Pd addressed at color converting address (R.sub.o, B.sub.o, G.sub.o), ((R.sub.o +1, B.sub.o, G.sub.o), (R.sub.o +1, B.sub.o +1, G.sub.o) and (R.sub.o, B.sub.o +1, G.sub.o) in that order, the second plane of the parallelepiped PP having four lattice points Pe, Pf, Pg and Ph addressed at color converting addresses (R.sub.o +1, B.sub.o +1, G.sub.o +1), (R.sub.o +2, B.sub.o +1, G.sub.o +1), (R.sub.o +2, B.sub.o +2, G.sub.o +1) and (R.sub.o +1, B.sub.o +2, G.sub.o +1) in that order, the color converting address (RH1', BH1', GH1') of the lattice point P1 of the selected rectangular parallelepiped agreeing with the color converting address (R.sub.o, B.sub.o, G.sub.o) of the lattice point Pa or the color converting address (R.sub.o +1, B.sub.o +1, G.sub.o +1) of the lattice point Pe in dependence on whether the value GH1' is an even number or an odd number, and the parallelepiped PP being formed of a first oblique triangular prism with the lattice points Pa, Pb, Pc, Pe, Pf and Pg and a second oblique triangular prism with the lattice points Pa, Pd, Pc, Pe, Ph and Pg;
• weighting factor generating means for generating a first weighting factor having a first value (RL1-GL1)' and a second weighting factor having a second value (BL1-GL1)' with the first, second and third lower color signals divided in the primary color signal dividing means, the value (RL1-GL1)' being equal to a value RL1-GL1 in case of RL1.gtoreq.GL1, the value (RL1-GL1)' being formed by adding a constant to the value (RL1-GL1) in case of RL1 <GL1, the value (BL1-GL1)' being equal to a value BL1-GL1 in case of BL1.gtoreq.GL1, and the value (BL1-GL1)' being formed by adding the constant to the value BL1-GL1 in case of BL1<GL1;
• oblique triangular prism selecting means for selecting either the first oblique triangular prism or the second oblique triangular prism of the parallelepiped PP of which the lattice point Pa agrees with the lattice point P1 of the selected rectangular parallelepiped specified in the adding means with the first weighting factor and the second weighting factor generated in the weighting factor generating means and generating an oblique triangular prism selecting signal indicating an oblique triangular prism selected;
• address generating means for generating eight block addresses of eight particular rectangular parallelepipeds, which each have one of eight selected lattice points agreeing with the lattice points Pa to Ph of the parallelepiped PP, with the selected block address (RH1', BH1', GH1') specified in the adding means, eight pieces of color converting data M0, M1, M2, M3, M4, M5, M6 and M7 allocated at the color converting addresses of the selected lattice points equivalent to the lattice points Pa to Ph of the parallelepiped PP being read out from the color converting data storing means;
• selecting means for selecting six pieces of color converting data from among the color converting data M0 to M7 as six pieces of color converting data Da, Db (or Dd), Dc, De, Df (Or Dh) and Dg allocated at the color converting addresses of the lattice points Pa, Pb (or Pd), Pc, Pe, Pf (or Ph) and Pg of the first or second oblique triangular prism of the parallelepiped PP in that order according to the oblique triangular prism selecting signal generated in the oblique triangular prism selecting means and the selected block address (RH1', BH1', GH1') specified in the adding means;
• and
• interpolation calculating means for interpolating coordinates of an output color defined in the output color space corresponding to input color coordinates of the input color as an output color value Do in the first or second oblique triangular prism of the parallelepiped PP with the six color converting data Da, Db (or Dd), Dc, De, Df (or Dh) and Dg selected in the selecting means while weighting the six color converting data with the first and second weighting factors generated in the weighting factor generating means and the lower third color signal divided in the primary color signal dividing means, the value (RL1-GL1)' of the first weighting factor denoting a first primary color component in the first primary color direction of an input color vector directed from the lattice point Pa to the input color coordinates, the value (BL1-GL1)' of the second weighting factor denoting a second primary color component in the second primary color direction of the input color vector, and the value GL1 of the lower third color signal denoting a third primary color component in the third primary color direction of the input color vector.

A color converting method for performing a three-dimensional color conversion of a colored picture, comprising the steps of:

• forming a plurality of rectangular parallelepipeds in a primary color space by partitioning the primary color space in a first primary color direction, a second primary color direction and a third primary color direction, each of the rectangular parallelepipeds having four lattice points P1, P2, P3 and P4 placed at a first-second primary color plane of the primary color space and other four lattice points P5, P6, P7 and P8 placed at another first-second primary color plane of the primary color space, and a block address of each of the rectangular parallelepipeds being represented by a color converting address of the lattice point P1;
• allocating pieces of color converting data defined in an output color space at the color converting addresses of the lattice points P1 to P8 of the rectangular parallelepipeds;
• receiving a first primary color signal, a second primary color signal and a third primary color signal defined in the primary color space and designating an input color;
• generating a color converting address (RH1', BH1', GH1') of a lattice point P1 of a selected rectangular parallelepiped with the first, second and third primary color signals;
• conceptually forming a parallelepiped PP in which the input color is included, the parallelepiped PP having a first plane placed at a value G.sub.o in the third primary color direction and a second plane parallel to the first plane, the first plane of the parallelepiped PP having four lattice points Pa, Pb, Pc and Pd addressed at color converting addresses (R.sub.o, B.sub.o, G.sub.o), (R.sub.o +1, B.sub.o, G.sub.o) (R.sub.o +1, B.sub.o +1, G.sub.o) and (R.sub.o, B.sub.o +1, G.sub.o) in that order, the second plane of the parallelepiped PP having four lattice points Pe, Pf, Pg and Ph addressed at color converting addresses (R.sub.o +1, B.sub.o +1, G.sub.o +1), (R.sub.o +2, B.sub.o +1, G.sub.o +1), (R.sub.o +2, B.sub.o +2, G.sub.o +1) and (R.sub.o +1, B.sub.o +2, G.sub.o +1) in that order, and the color converting address (RH1', BH1', GH1') of the lattice point P1 of the selected rectangular parallelepiped agreeing with the color converting address (R.sub.o, B.sub.o, G.sub.o) of the lattice point Pa or the color converting address (R.sub.o +1, B.sub.o +1, G.sub.o +1) of the lattice point Pe in dependence on whether the value GH1' is an even number or an odd number;
• conceptually partitioning the parallelepiped PP into a first oblique triangular prism with the lattice points Pa, Pb, Pc, Pe, Pf and Pg and a second oblique triangular prism with the lattice points Pa, Pd, Pc, Pe Ph and Pg;
• reading out six pieces of color converting data Da, Db (or Dd), Dc, De, Df (or Dh) and Dg allocated at the color converting addresses of the lattice points Pa, Pb (or Pd), Pc, Pe, Pf (or Ph) and Pg of the first or second oblique triangular prism in which the input color is included;
• and
• interpolating an output color defined in the output color space corresponding to the input color in the selected oblique triangular prism of the parallelepiped PP with the six color converting data Da, Db (or Dd), Dc, De, Df (or Dh) and Dg.

A color converting method for performing a three-dimensional color conversion of a colored picture, comprising the steps of:

• forming a plurality of rectangular parallelepipeds in a primary color space by partitioning the primary color space in a first primary color direction, a second primary color direction and a third primary color direction, each of the rectangular parallelepipeds having four lattice points P1, P2, P3 and P4 placed at a first-second primary color plane of the primary color space and other four lattice points P5, P6, P7 and P8 placed at another first-second primary color plane of the primary color space, and a block address of each of the rectangular parallelepipeds being represented by a color converting address of the lattice point P1;
• allocating pieces of color converting data defined in an output color space at the color converting addresses of the lattice points P1 to P8 of the rectangular parallelepipeds;
• receiving a first primary color signal, a second primary color signal and a third primary color signal defined in the primary color space and designating an input color;
• generating a color converting address (RH1', BH1', GH1') of a lattice point P1 of a selected rectangular parallelepiped with the first, second and third primary color signals;
• conceptually forming a first type of parallelepipeds and a second type of parallelepipeds to occupy all of the primary color space, the first type of parallelepipeds respectively having a first plane placed at a value G.sub.o in the third primary color direction and a second plane parallel to the first plane, the first plane of the first type of parallelepiped having four lattice points Pa, Pb, Pc and Pd addressed at color converting addresses (R.sub.o, B.sub.o, G.sub.o), (R.sub.o +1, B.sub.o +1, G.sub.o), (R.sub.o +1, B.sub.o +2, G.sub.o) and (R.sub.o, B.sub.o +1, G.sub.o) in that order, the second plane of the first type of parallelepiped having four lattice points Pe, Pf, Pg and Ph addressed at color converting addresses (R.sub.o +1, B.sub.o +1, G.sub.o +1), (R.sub.o +2, B.sub.o +2, G.sub.o +1), (R.sub.o +2, B.sub.o +3, G.sub.o +1) and (R.sub.o +1, B.sub.o +2, G.sub.o +1) in that order, the second type of parallelepipeds respectively having a third plane placed at a value G.sub.o ' in the third primary color direction and a fourth plane parallel to the third plane, the third plane of the second type of parallelepiped having four lattice points Pa', Pb', Pc' and Pd' addressed at color converting addresses (R.sub.o ', B.sub.o ', G.sub.o '), (R.sub.o '+1, B.sub.o ', G.sub.o '), (R.sub.o '+2, B.sub.o '+1, G.sub.o ') and (R.sub.o '+1, B.sub.o '+ 1, G.sub.o ') in that order, the fourth plane of the second type of parallelepiped having four lattice points Pe', Pf', Pg' and Ph' addressed at color converting addresses (R.sub.o '+1, B.sub.o '+1, G.sub.o '+1), (R.sub.o '+2, B.sub.o '+1, G.sub.o '+1), (R.sub.o '+3, B.sub.o '+2, G.sub.o '+1) (R.sub.o '+2, B.sub.o '+2, G.sub.o '+1) in that order, the color converting address (RH1'BH1'GH1') of the lattice point P1 of the selected rectangular parallelepiped agreeing with the color converting address (R.sub.o, B.sub.o, G.sub.o) of the lattice point Pa, the color converting address (R.sub.o +1, B.sub.o +1, G.sub.o +1) of the lattice point Pe, the color converting address (R.sub.o ', B.sub.o ', G.sub.o ') of the lattice point Pa', or the color converting address (R.sub.o '+1, B.sub.o '+1, G.sub.o '+1) of the lattice point Pe' in a particular parallelepiped in dependence on whether the value GH1' is an even number or an odd number, and the input color designated by the three primary color signals being included in the particular parallelepiped;
• reading out eight pieces of color converting data Da, Db, Dc, Dd, De, Df, Dg and Dh allocated at the color converting addresses of the lattice points Pa, Pb, Pc, Pd, Pe, Pf, Pg and Ph or Pa', Pb', Pc', Pd', Pe', Pf', Pg' and Ph' of the particular parallelepiped;
• and
• interpolating an output color defined in the output color space corresponding to the input color with the eight color converting data Da, Db, Dc, Dd, De, Df, Dg and Dh.