EP0622952A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
A method and a device for generating printing data
Assignee: Barco Graphics NV
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Filing: 1994-04-28
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Granted: —
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Expires: 2014-04-28
Abstract
Abstract A method and a device for generating printing data wherein a first colour separation defined in a first device dependent colour space is converted into a second colour separation defined in a second device dependent colour space of non-standard printing inks. The conversion is realised by means of a conversion matrix which is multiplied with the first colour separation.
Inventors
- 👤 Lieven Plettinck
- 👤 Jean-Pierre Van De Capelle
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 18:03
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/54; H04N1/56; H04N1/60; H04N1/603; H04N1/6052; H04N1/6055
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
271 words
A method for generating printing data wherein, starting from a first colour separation of a pixel belonging to a picture to be printed, picture which is defined in a first n-dimensional device dependent colour space, a second colour separation is formed for that same pixel, said second colour separation being defined in a second m-dimensional device dependent colour space of non-standard printing inks, characterised in that a colour separation derived from a standard colour separation is determined as first colour separation and a set of p(p≧n) different colours is chosen which belong to the colour gamut of the second colour space on at least a predetermined colour distance of each other, and wherein a first, respectively a second colour table is determined representing for each colour of the set the colour coordinates expressed in coordinates of the colour space used to represent the first colour separation respectively representing the m colour coordinates in the second device dependent colour space, and wherein a first p by p matrix is formed having for p ij th (1≦i≦p ; 1≦j≦p) matrix coefficient the j th colour coordinate of the i th colour such as represented in the first table, and thereafter a second m by p matrix is formed by taking for a q th row (1≦q≦m) of that second matrix the coefficients obtained multiplying the inverted first matrix with a third p by 1 matrix representing the q th colour separation of the second colour space of the different colours belonging to the set of p colours, which second colour separation is determined by multiplying the second matrix by the first colour separation.
Claim 2
Dependent Claim
141 words
A method as claimed in claim 1, characterised in that the first, respectively the second colour separation is transformed to a first respectively a second colour coordinate set by means of a predetermined mapping fixing the relation between the first, respectively the second device dependent colour space and a first, respectively a second device independent colour space, and wherein in the second device independent colour space a "Soll - colour coordinate set" is formed by mapping said first colour coordinate set towards that second device independent colour space, and wherein thereafter a target function expressed in the second colour separation is determined from the Soll-colour coordinate set and the second colour coordinate set, which target function is subsequently minimised, a further second colour separation is determined with the minimised target function, which further second colour separation substitutes said second colour separation.
Claim 3
Dependent Claim
218 words
A method as claimed in claim 1, characterised in that, for the picture to be printed, a first set of first colour separations is formed in the first device dependent colour space and a second set of second colour separations is formed in the second device dependent colour space by multiplying each time each first colour separation from the first set with said second matrix, and wherein a third, respectively a fourth set is formed by each time transforming each of the first, respectively second colour separations from the first, respectively second set to each time a first, respectively a second colour coordinate set by means of a predetermined mapping establishing the relation between the first, respectively the second device independent colour space, and wherein a fifth set of "Soll-colour coordinate sets" is formed in the second device independent colour space by mapping towards that second device independent colour space each of the colour coordinate sets of the third set, and wherein thereafter a target function expressed with the coefficients of the second matrix is each time determined for each of the Soll-colour coordinate sets of the fifth set and each of the colour coordinate sets of the fourth set, which target function is thereafter minimised and a further second matrix being determined with the minimised target function.
Claim 4
Dependent Claim
151 words
A method as claimed in claim 3, characterised in that a further second colour separation is determined by means of a matrix multiplication of the further second matrix and the first colour separation, which first, respectively further second colour separation is mapped towards the first, respectively second device independent colour space by means of said mapping in order to form there a first, respectively a further second colour coordinate set, which first colour coordinate set is mapped towards the second device independent colour space in order to form there a Soll-colour coordinate set, and wherein a target function expressed in the further second colour separation is determined from the Soll-colour coordinate set and the further second colour coordinate set, which target function is thereafter minimised and a still further second colour separation being determined with the minimised target function, which still further second colour separation substitutes said further second colour separation.
Claim 5
Independent Claim
43 words
A method as claimed in one of the claims 2, 3, or 4, characterised in that the colour distance between the Soll-colour coordinate set and the second colour coordinate set is determined and wherein said target function is determined from that colour distance.
Claim 6
Dependent Claim
28 words
A method as claimed in claim 2, 3 or 4, characterised in that said minimisation comprises a minimisation of the Euclidian distance in a perceptual uniform colour space.
Claim 7
Dependent Claim
121 words
A method as claimed in claim 2 to 6, characterised in that if the dimension of the second device dependent colour space is larger than three, for the b th (b>3) colours those colours are selected of which the values of the gradient norm of the second colour coordinate set expressed as a function of the second colour separation is the smallest, and wherein for the thus selected colours the second colour separation coefficient is chosen as target value and a further target function is determined from the Soll-colour coordinate set, the second colour coordinate set and the target value, which further target function is thereafter minimised and a modified second colour separation being determined with the minimised further target function.
Claim 8
Dependent Claim
22 words
A method as claimed in claim 7, characterised in that weight coefficients are attributed to the variables of said further target function.
Claim 9
Independent Claim
54 words
A method as claimed in anyone of the claims 2 to 8, characterised in that a second colour separation set is built by each time, after determination of a second colour separation after minimisation, storing the latter in a memory, as the deviation between the Soll-colour coordinate set and the second colour coordinate set.
Claim 10
Dependent Claim
71 words
A method as claimed in claim 9, characterised in that tables are stored in the memory, and wherein a set of non-standard printing inks is associated to each table, and the second colour separations corresponding to the first colour separations of the set of non-standard printing inks belonging to a table are each time stored in that table, even as the deviation between Soll-colour coordinate set and second colour coordinate set.
Claim 11
Dependent Claim
144 words
A method as claimed in claim 10, characterised in that by printing said picture, a further set of first colour separations of pixels belonging to said picture is determined and for each first colour separation of said further set a still further set of second colour separations is determined each time by selecting each time the corresponding second colour separation and the deviation from each of the tables, and wherein thereafter for each set of non-standard inks an average value of the deviation is determined from each deviations of that element with the still further set, and among said average values the one with the lowest value is chosen and the set of non-standard inks belonging thereto is chosen, and thereafter for each first colour separation and the chosen set of non-standard inks the second colour separation is determined by means of the table.
Claim 12
Dependent Claim
42 words
A device provided for application of the method as claimed in claim 1 to 11, characterised in that it comprises a conversion unit provided with conversion means for forming said second matrix and said second color separations from said first color separation.
Claim 13
Dependent Claim
42 words
A device as claimed in claim 11, and provided for the application of a method as claimed in anyone of the claims 2 to 8, characterised in that it comprises a target function generator provided for determining and minimising said target function.
Claim 14
Dependent Claim
40 words
A device provided for the application of the method according to claim 9, characterised in that it comprises a memory provided for storing said second matrix and said second colour separation and the deviation belonging to that second colour separation.
Claim 15
Dependent Claim
39 words
A device provided for application of the method according to claim 10, characterised in that it is provided with selection means affected to the selection on the basis of said deviation of said second colour separation to be fetched.
References Cited (Backward Citations)
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