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Claims  |
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What is claimed is:
1. 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 the color converting data
having a value limited to an even number or an odd number in a widened
range, 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 prism 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, Dr (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 a displacement register for registering a
positive or negative displacement value, a displacement adder for adding
the displacement value registered in the displacement register to the
output color value Do to set the widened range of the output color value
Do interpolated with the color converting data Da, Db (or Dd), Dc, De, Df
(or Dh) and Dg in a displace range which equally occupies an area of
positive numbers and another area of negative numbers, and an output data
limiter for limiting the output color value Do set in the displace range
by the displacement adder within an area of positive numbers and zero.
2. A color converting apparatus according to claim 1 in which the color
converting data storing means comprises a plurality of color converting
tables which each correspond to one of the rectangular parallelepipeds,
each of the color converting tables comprising a first color converting
memory for storing the color converting data Da, a second color converting
memory for storing the color converting data Db at a first bank and the
color converting data Dd at a second bank, a third color converting memory
for storing the color converting data Dc, a fourth color converting memory
for storing the color converting data De, a fifth color converting memory
for storing the color converting data Df at a first bank and the color
converting data Dh at a second bank, and a sixth color converting memory
for storing the color converting data Dg.
3. A color converting apparatus according to claim 1 in which the color
converting data storing means comprises a plurality of color converting
tables which each correspond to one of the rectangular parallelepipeds,
each of the color converting tables comprising a first color converting
memory for storing the color converting data Da at a first color
converting sub-table and another piece of color converting data Da' at a
second color converting sub-table, a first bank of second color converting
memory for storing the color converting data Db at a first color
converting sub-table and another piece of color converting data Db' at a
second color converting sub-table, a second bank of second color
converting memory for storing the color converting data Dd at a first
color converting sub-table and another piece of color converting data Dd'
at a second color converting sub-table, a third color converting memory
for storing the color converting data Dc at a first color converting
sub-table and another piece of color converting data Dc' at a second color
converting sub-table, a fourth color converting memory for storing the
color converting data De at a first color converting sub-table and another
piece of color converting data De' at a second color converting sub-table,
a first bank of fifth color converting memory for storing the color
converting data Df at a first color converting sub-table and another piece
of color converting data Df' at a second color converting sub-table, a
second bank of fifth color converting memory for storing the color
converting data Dh at a first color converting sub-table and another piece
of color converting data Dh' at a second color converting sub-table, and a
sixth color converting memory for storing the color converting data Dg at
a first color converting sub-table and another piece of color converting
data Dg' at a second color converting sub-table, either the color
converting data Da, Db (or Dd), Dc, De, Df (or Dh) and Dg stored at the
first color converting sub-tables or the color converting data Da', Db'
(or Dd'), Dc', De', Df' (or Dh') and Dg' stored at the second color
converting sub-tables being read out from the color converting data
storing means as the color converting data Da, Db (or Dd), Dc, De, Df (or
Dh) and Dg.
4. A color converting apparatus according to claim 3, further including:
area processing selecting means for selecting either a first type of area
processing in which a first type of color conversion is performed for a
first area of a colored picture or a second type of area processing in
which a second type of color conversion is performed for a second area of
the colored picture; and
sub-table signal generating means for generating a first sub-table signal
in cases where the first type of area processing is selected in the area
processing selecting means and generating a second sub-table signal in
cases where the second type of area processing is selected in the area
processing selecting means, the first or second sub-table signal being
transferred to the address generating means, the color converting data Da,
Db (or Dd), Dc, De, Df (or Dh) and Dg stored at the first color converting
sub-tables being read out from the color converting data storing means in
cases where the first sub-table signal is transferred to the address
generating means, and the color converting data Da', Db' (or Dd'), Dc',
De', Df' (or Dh') and Dg' stored at the second color converting sub-tables
being read out from the color converting data storing means as the color
converting data Da, Db (or Dd), Dc, De, Df (or Dh) and Dg in cases where
the second sub-table signal is transferred to the address generating
means.
5. A color converting apparatus according to claim 1 in which a lightness Y
of a colored picture indicated by the input lightness signal Y, a first
color difference Cr of the colored picture indicated by the input first
color difference signal Cr and a second color difference Cb of the colored
picture indicated by the input second color difference signal Cb are
expressed with three primary colors such as a red R, a green G and a blue
B according to equations:
Y=0.2990*R+0.5864*G+0.1146*B,
Cr=R-Y,
and
Cb=B-Y.
6. A color converting apparatus according to claim 1 in which a value Y1 of
the input lightness signal Y, a value Cr1 of the input first color
difference signal Cr and a value Cb1 of the input second color difference
signal Cb are respectively expressed by a piece of 10-bit input data.
7. A color converting apparatus according to claim 1 in which the input
lightness signal Y, the input first color difference signal Cr and the
input second color difference signal Cb are respectively composed of a
sequence of bits, the upper signals UY, UCr and UCb are respectively
composed of 3 bits according to a normal mode to form the
8.times.8.times.8 rectangular parallelepipeds by partitioning the
lightness-color difference space into 8 pieces in each of the lightness
direction, the first color difference direction and the second color
difference direction, and the upper signals UY, UCr and UCb are
respectively composed of 3 bits according to a normal mode to form the
8.times.8.times.8 rectangular parallelepipeds by partitioning the
lightness-color difference space into 8 pieces in each of the lightness
direction, the first color difference direction and the second color
difference direction, and the upper lightness signal UY composed of 4 bits
and the upper color difference signals UCr and UCb respectively composed
of 3 bits are received in the address generating means according to an
address extending mode to form the 16.times.8.times.8 rectangular
parallelepipeds by partitioning the lightness-color difference space into
16 pieces in the lightness direction and partitioning the lightness-color
difference space into 8 pieces in each of the first color difference
direction and the second color difference direction.
8. A color converting apparatus according to claim 1 in which the selection
of either the first triangular prism or the second triangular prism in the
triangular prism selecting means is performed by comparing the value DCr1
of the lower first color difference signal DCr and the value DCb1 of the
lower second color difference signal DCb.
9. A color converting apparatus according to claim 1 in which the color
converting data are respectively composed of 10 bits,
the widened range of the output color value Do added in the displacement
adder is from -1024 to 1022, and
the output color value Do limited in the output data limiter ranges from 0
to 1023.
10. A color converting apparatus according to claim 1 in which the color
converting data are respectively composed of 8 bits,
the widened range of the output color value Do added in the displacement
adder is from -256 to 254, and
the output color value Do limited in the output data limiter ranges from 0
to 255.
11. A color converting apparatus according to claim 4 in which the area
processing selecting means comprises:
an area RAM table for storing a starting address of a starting pixel placed
at a starting point of the first area of the colored picture and an ending
address of an ending pixel placed at an ending point of the first area of
the colored picture, the starting address and the ending address being
numbered an area number;
a pixel counter for counting pixels along a main scanning line to specify
addresses of the pixels;
a pixel address comparator for comparing the addresses of the pixels
counted in the pixel counter with the starting address or the ending
address stored in the area RAM table to judge whether or not each of the
addresses of the pixels scanned along the main scanning line accords with
the starting address or the ending address and generating an area counting
signal each time an address of a pixel scanned along the main scanning
line accords with the starting address or the ending address; and
an area counter for counting the area counting signal generated in the
pixel address comparator to increase an area number one by one and sending
an increased area number to the area RAM table, a selecting signal
instructing the performance of the first type of color conversion being
transferred to the sub-table signal generating means in cases where the
increased area number accords with the area number given to the starting
address, another selecting signal instructing the performance of the
second type of color conversion being transferred to the sub-table signal
generating means in cases where the increased area number accords with the
area number given to the ending address, and the starting address and the
ending address stored in the area RAM table being rewritten with other
starting and ending addresses transferred from a host computer each time
all of the pixels placed in one of the main scanning line are counted in
the pixel counter.
12. A color converting apparatus according to claim 1, further including:
host interface means for transferring other pieces of color converting data
from a host computer to the color converting data storing means to renew
the color converting data stored in the color converting data storing
means during a blanking period in which the color converting data Da, Db
(or Dd), Dc, De, Df (or Dh) and Dg are not read out from the color
converting data storing means.
13. A color converting apparatus according to claim 1, further including:
lightness and color difference generating means for generating the input
lightness signal Y, the input first color difference signal Cr and the
input second color difference signal Cb from a first primary color signal,
a second primary signal and a third primary signal defined in a primary
color space.
14. A color converting apparatus according to claim 13 in which the
lightness and color difference generating means comprises:
a first subtracting element for subtracting a second value G1 of the second
primary color signal from a first value R1 of the first primary color
signal to generate the input first color difference signal Cr; and
a second subtracting element for subtracting the second value G1 of the
second primary color signal from a third value B1 of the third primary
color signal to generate the input second color difference signal Cb.
15. A color converting apparatus according to claim 13 in which the
lightness and color difference generating means comprises:
a lightness generating element for generating the input lightness signal Y
linearly independent of both the input first color difference signal Cr
and the input second color difference signal Cb by combining the first
primary color signal, the second primary color signal and the third
primary color signal.
16. A color converting apparatus according to claim 15 in which a value Y1
of the input lightness signal Y is expressed with the values R1, G1 and B1
according to an equation selected from three equations:
Y1=(R1+G1+B1)/3, Y1=(R1+2*G1+B1)/4,
and
Y1=G1.
17. A color converting apparatus according to claim 14, further including:
a first negative value compensating element for compensating the input
first color difference signal Cr generated in the first subtracting
element for a negative value generated in the first subtracting element to
form the input first color difference signal Cr having a value of zero or
a positive number, the value of the input first color difference signal Cr
denoting a density of a first color difference in the input color; and
a second negative value compensating element for compensating the input
second color difference signal Cb generated in the second subtracting
element for a negative value generated in the second subtracting element
to form the input second color difference signal Cb having a value of zero
or a positive number, the value of the input second color difference
signal Cr denoting a density of a second color difference in the input
color.
18. 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.
19. 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 e | | |
