WO2002096093A1 - Procede de reglage des couleurs d'une image en vue de son impression - Google Patents

Procede de reglage des couleurs d'une image en vue de son impression Download PDF

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Publication number
WO2002096093A1
WO2002096093A1 PCT/IT2001/000263 IT0100263W WO02096093A1 WO 2002096093 A1 WO2002096093 A1 WO 2002096093A1 IT 0100263 W IT0100263 W IT 0100263W WO 02096093 A1 WO02096093 A1 WO 02096093A1
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WO
WIPO (PCT)
Prior art keywords
colour
image
pixel
pixels
space
Prior art date
Application number
PCT/IT2001/000263
Other languages
English (en)
Inventor
Mauro Cestari
Original Assignee
Tyke Int'l S.R.L.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tyke Int'l S.R.L. filed Critical Tyke Int'l S.R.L.
Priority to PCT/IT2001/000263 priority Critical patent/WO2002096093A1/fr
Publication of WO2002096093A1 publication Critical patent/WO2002096093A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/46—Colour picture communication systems
    • H04N1/56—Processing of colour picture signals
    • H04N1/60—Colour correction or control
    • H04N1/6097—Colour correction or control depending on the characteristics of the output medium, e.g. glossy paper, matt paper, transparency or fabrics
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/46—Colour picture communication systems
    • H04N1/54—Conversion of colour picture signals to a plurality of signals some of which represent particular mixed colours, e.g. for textile printing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/46—Colour picture communication systems
    • H04N1/56—Processing of colour picture signals
    • H04N1/60—Colour correction or control
    • H04N1/6016—Conversion to subtractive colour signals

Definitions

  • the present invention relates to a method of controlling colours of an image for printing, and is directed towards the conversion of the colours of the image from a first, input colour space to a second, output colour space, according to the preamble to main Claim 1.
  • the conversion of the colours of the monitor image into printer colours is complex since the monitor colour space (the additive mixture of the colours red R, green G and blue B, the so-called RGB space) and the printer colour space (the subtractive mixture of the colours cyan C, magenta M, yellow Y and black K, the so-called CMYK space) are not superimposable .
  • the RGB colour space is more extensive than the CMYK colour space.
  • the main object of the present invention is to provide a method of controlling the colour of images for printing, particularly on materials such as wood and ceramic materials, which is designed to overcome the limitations discussed with reference to the prior art mentioned.
  • FIG. 1 is a schematic view of a device for controlling the colours of an image, operating in accordance with the method of the invention
  • FIG. 2 is a flow chart showing schematically some of the steps of the method of the invention.
  • FIG. 3 is a schematic structural diagram showing, by way of example, some of the steps of the method of the invention.
  • means for controlling the colours of an image 2 are indicated 1 and comprise a computer la on the monitor 3 of which the image 2 is displayed.
  • the file 2a containing the data relating to the image 2 is stored in a memory 4 accessible to the computer la.
  • the monitor 3 is of a standard type, that is, with a rectangular matrix of pixels 7 (shown schematically in Figure 3) the colours of which are determined by mixtures of predetermined quantities of red (R) , green (G) and blue (B) components which constitute a base in a first, monitor colour space, that is, the RGB input space.
  • a set of three colour coordinates (R,G,B) is thus associated with the colour of each pixel, each coordinate being given by a number which is variable from 0 to 255 and represents the "quantity" of red, green or blue present in the colour of the pixel in question.
  • the image 2 displayed on the monitor 3 is converted into a multi-channel bitmap file 20 which can be printed by the printer 5 to produce, on the substrate 6, by the method according to the invention described in detail below with reference to the flow chart of Figure 2, an accurate reproduction of the colours displayed on the monitor 3.
  • the user enters in the memory 4, or in an additional memory 13 accessible to the computer la, the components of a suitable base in a second, output colour space (step 100 of the flow chart of Figure 2) which are defined by their RGB coordinates.
  • the components of this base are selected in dependence on the material constituting the substrate 6 on which the image is printed.
  • the components of the base correspond to non- toxic colours which are not liable to alteration in subsequent stages of the processing of the substrate 6 and are commercially available for the colouring of the selected material .
  • These components of the base of the second colour space correspond to the inks available in the printer 5.
  • an image 10 enlarged N times (in Figure 3, N equals 3) is associated with the digital image 2 stored in the memory 4 (step 101 of the flow chart of Figure 2) .
  • each pixel 7 of the starting image 2 is associated with N 2 pixels 7a of the enlarged image 10, each of which is attributed the same colour coordinates (R, G, B) as the pixel 7.
  • a first pixel P x is then selected in the enlarged image 10 (step 102) and the colour coordinates (R,G,B) of the R, G, B components of its colour in the first colour space of the monitor 3 are determined.
  • the percentage at which each component of the base of the second colour space is present in the colour of the selected pixel P x is determined (step 103) by a comparison of the colour coordinates (R, G, B) of P x with the stored components of the second colour space.
  • the predominant component amongst them that is, the component having the highest percentage, is identified (step 104) .
  • the colour of the pixel P x is thus identified by means of the percentages of the second colour-space components, that is, new colour coordinates in the second colour space are associated with the pixel P x .
  • the first pixel P x is thus associated (step 105) with a monochrome pixel P M having as its colour purely the predominant component of the colour of the first pixel P x , that is, 100% of its colour is equal to the predominant component of the colour of )? 1 .
  • pixels of the enlarged image 10 are also correlated with the first pixel P x and their colours are modified in dependence on the components of the second colour space which are present in the first pixel P x in percentages other than the highest (step 106) . More particularly, the correlated pixels correspond to pixels P ⁇ geometrically adjacent the first pixel P x . If P x is not part of an edge of the enlarged image 10, there are 8 adjacent pixels and only some of them have their colour coordinates modified, as described below.
  • the values of the percentages present other than the highest percentage are divided into a number of fractions equal to the number of modifiable adjacent pixels, that is, those adjacent pixels with which a monochrome pixel has not previously been associated.
  • the colours of the modifiable adjacent pixels are consequently modified by increasing, in proportion to the above-mentioned fractions, the percentage values of those components which have percentages other than the highest percentage in the first pixel .
  • Steps 102-106 are then repeated for a plurality of pixels 7a included, for example, within a predefined area of the enlarged image 10, or for all of the pixels of the enlarged image 10 (step 107) , so as to obtain a second image 15 formed exclusively by monochrome pixels P M in the second colour space .
  • the pixels 7a are selected sequentially, starting with a pixel having a predetermined arbitrary position and continuing with the selection of the pixels 7a disposed along a row.
  • bitmap channel 19 is created for them (step (108) .
  • This step is performed for all of the components of the second colour space and a number of bitmap channels, all indicated 19, equal to the number of components the second space is thus created.
  • Each bitmap channel 19 is constituted by a matrix with a number of pixels P c equal to that of the enlarged image 15. For each pixel P c , there is a corresponding bit which may have only two states: white or black.
  • a bit associated with a pixel P c of a bitmap channel 19 of a predetermined component is black if the corresponding pixel P M in the same position in the monochrome image 15 has a colour given by 100% of the component of the bitmap channel; otherwise it is white.
  • the above-mentioned plurality of bitmap channels is combined in a single multi-channel bitmap file 20 (step 109) .
  • the resolution is then reduced N times, thus changing from bitmap to grey scale (step 110) .
  • a single pixel is associated with N 2 pixels of the multichannel bitmap 20 and its colour is given by the superimposition of the colours (white or black) of the N 2 starting pixels.
  • the multi-channel bitmap file 20 is then sent to the printer 5 for printing on the substrate 6.
  • FIG. 3 A practical example of the colour control of a pixel of the image 2 by means of the above-described method according to the invention is shown schematically in Figure 3.
  • the components of the base of the second colour space are given by: C(0,200,255) , M(200, 0, 127) , 0(200,40,0), Y(255, 200, 0) , G 1 (0,200,0), K(0,0,0).
  • This base is used particularly for vinyl-sheet and ceramic substrates 6.
  • the pixel P x is then associated with the monochrome pixel P M which contributes to the generation of the second monochrome image 15, the colour of which is given by 100% of C.
  • the colour of each of the adjacent pixels is thus modified in dependence on these fractions and is equal to (20% of C, 0, 0, 0, 0, 0, 18 + 9% of K) for P m ⁇ , as well as for P ⁇ and P ⁇ .
  • the pixel P KD1 is then selected as the first pixel t? 1 ' and the monochrome pixel P M ' having 100% of K is associated therewith since, in this case, the predominant component is the component K.
  • the colours of the adjacent pixels are thus modified in dependence on fractions of values equal to 5% for component C.
  • a second image 15 composed of monochrome pixels in the components set for the second colour space is thus obtained.
  • 7 bitmap channels 19 are thus created, one for each second colour-space component, and these are grouped in a single multi-channel bitmap file 20.
  • Figure 3 shows a portion of the C bitmap channel given by 4 black pixels P c and 5 white ones.
  • the multi-channel bitmap 20, stored in the memory 4 or 13, is printed on the substrate 6 by means of the printer 5.
  • data relating to the basic background colour/s of the preselected coloured material, in particular its RGB colour coordinates are entered in the memory 4 or 13.
  • the aforesaid colour is then converted into the second colour space and the resulting components are subtracted from the colours of the pixels of the image. For example, if the background colour is given by 5% Y and 20% K, these percentage values are subtracted from each pixel of the image.
  • the invention thus achieves the objects proposed, offering many advantages over known solutions.
  • the method according to the invention enables the colours of an image to be controlled automatically in order to obtain an accurate reproduction of them upon printing.
  • the colour control is thus very quick and can be reproduced an arbitrary number of times without the need for skilled personnel such as graphic designers.
  • the method according to the invention also enables images to be printed on a large variety of materials, nevertheless producing a reasonably accurate reproduction of the colours on each of them.
  • the method according to the invention permits printing on coloured materials without colour distortion in relation to the image displayed on the computer monitor.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Textile Engineering (AREA)
  • Accessory Devices And Overall Control Thereof (AREA)

Abstract

L'invention concerne un procédé de réglage des couleurs d'une image en vue de son impression, les couleurs de cette image étant converties d'un premier espace couleur d'entrée en un second espace couleur de sortie. Ce procédé consiste d'abord à sélectionner (102) un premier pixel (P1) de l'image, à déterminer ensuite les coordonnées couleur de la couleur du premier pixel (P1) qui sont associées aux composantes d'une base du premier espace couleur, à déterminer les composantes du second espace couleur en fonction du matériau sur lequel l'image est imprimée, à déterminer (103) les coordonnées couleur de la couleur du premier pixel (P1) qui sont associées aux composantes d'une base du second espace couleur déterminées, à associer (105) au premier pixel un pixel monochrome (Pm) d'une couleur définie par la composante de la base du second espace présentant (104) la coordonnée couleur de la valeur la plus élevée dans le premier pixel (P1), et enfin, à reprendre toutes les opérations précédentes (102-105) pour une pluralité de pixels (7a) de l'image pour obtenir une seconde image composée des pixels monochromes (Pm) dans le second espace couleur.
PCT/IT2001/000263 2001-05-24 2001-05-24 Procede de reglage des couleurs d'une image en vue de son impression WO2002096093A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/IT2001/000263 WO2002096093A1 (fr) 2001-05-24 2001-05-24 Procede de reglage des couleurs d'une image en vue de son impression

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/IT2001/000263 WO2002096093A1 (fr) 2001-05-24 2001-05-24 Procede de reglage des couleurs d'une image en vue de son impression

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WO2002096093A1 true WO2002096093A1 (fr) 2002-11-28

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0660589A2 (fr) * 1993-12-21 1995-06-28 Nec Corporation Appareil de formation d'images en couleur capable de produire une qualité d'image uniforme et solide pour les milieux d'enregistrement divers
US5933578A (en) * 1997-04-08 1999-08-03 Barco Graphics, N.V. Method and device for determining the color appearance of color overprints
EP0962329A1 (fr) * 1997-02-05 1999-12-08 Truetone S.L. Procede pour l'application de couleurs et de tonalites sur differentes surfaces
EP1079606A2 (fr) * 1999-08-11 2001-02-28 Canon Kabushiki Kaisha Ajustement de l'espace chromatique pour plusieurs substrats

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0660589A2 (fr) * 1993-12-21 1995-06-28 Nec Corporation Appareil de formation d'images en couleur capable de produire une qualité d'image uniforme et solide pour les milieux d'enregistrement divers
EP0962329A1 (fr) * 1997-02-05 1999-12-08 Truetone S.L. Procede pour l'application de couleurs et de tonalites sur differentes surfaces
US5933578A (en) * 1997-04-08 1999-08-03 Barco Graphics, N.V. Method and device for determining the color appearance of color overprints
EP1079606A2 (fr) * 1999-08-11 2001-02-28 Canon Kabushiki Kaisha Ajustement de l'espace chromatique pour plusieurs substrats

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