CN100576067C - Colorful picture six color separation printing method - Google Patents

Abstract

The present invention relates to a kind of colorful picture six color separation printing method, can effectively solve and use under existing equipment and the technical conditions printed matter color not bright-coloured full, version of all kinds is easy to generate the problem of hitting the net phenomenon, the technical scheme of its solution is, with original copy through being scanned into the digital picture of RGB color mode, pass through color space conversion afterwards, become the digital picture of CIELAB color mode, use the six color separation algorithm to be broken down into yellow again, magenta, cyan, black, orange and green six color separation version data, after this data process raster image processor interpretation process, be output into the screening film with the film setter am screening, become galley by the printer printing down again, by press printing, or by direct platemaking machine am screening output, directly plate-making, become printed matter by press printing, the present invention can improve the quality of printed matter greatly, the printed matter bright and full color that obtains, version of all kinds does not produce hits the net phenomenon, is particularly suitable for printing high-end elaboration living-article.

Description

Colorful picture six color separation printing method

One, technical field

The present invention relates to a kind of printing process, particularly a kind of colorful picture six color separation printing method.

Two, background technology

For a long time, yellow, magenta, cyan, black four-color process are used in colored printing always, but the defective of this printing technology is undesirable to brightly painted printed matter performance, there is sizable gap in the color of printed matter and photo, further raising along with social demand, the number to be printed of high-end elaboration living-article is more and more, only adopts four-color process to seem unable to do what one wishes, and polychrome printing color separation printing technology is arisen at the historic moment.

Make a plate period in photo colour separation,, can't realize the polychrome color separation at that time because simulation color separation technology level is limit; In electric separation machine Color Separate printing stencil making period, the technical method of seven looks printing once appearred realizing with the color filter color separation, just do not divide eliminating of plate-making technology and disappear but enter practical application as yet, the substitute is a kind of brand-new digital color separation mode under the digital publishing technical conditions along with electricity.

In present employed digital color separation technology, generally adopted look-up table to realize color separation, and, when output, must use the fm screening technology again, to avoid the net phenomenon occurring hitting after the version printing of all kinds for the color separation data that surpass four looks.But,, too high to the technical conditions requirement of each link of print production because the physical dimension of frequency-modulation halftone dot is too little, use to modulating net has suitable limitation, the printing house of general strength is difficult to reach technical requirement, therefore, also just can't accept the polychrome printing business.

Three, summary of the invention

At above-mentioned situation, the present invention's purpose is to provide a kind of colorful picture six color separation printing method, can effectively solve and use under existing equipment and the technical conditions printed matter color not bright-coloured full, version of all kinds is easy to generate the problem of hitting the net phenomenon, the technical scheme of its solution is, with original copy through being scanned into RGB (RGB, as follows) digital picture of color mode has been (if be the RGB color mode, just needn't scan again), pass through color space conversion afterwards, become the digital picture of CIELAB color mode, use the six color separation algorithm to be broken down into yellow again, magenta, cyan, black, orange and green six color separation version data, after this data process raster image processor (RIP) interpretation process, be output into the screening film, become galley by the printer printing down again with the film setter am screening, by press printing, or by direct platemaking machine am screening output, directly plate-making becomes printed matter by press printing.Use existing equipment and technical conditions just can realize the printing that six looks high-end elaboration is lived by the inventive method, when effectively utilizing existing printing resource, improve the quality of printed matter greatly, the printed matter bright and full color of utilizing the inventive method to obtain, version of all kinds does not produce hits the net phenomenon, is particularly suitable for printing high-end elaboration living-article.

Four, description of drawings

Fig. 1 is a six color separation printing technology method flow diagram of the present invention.

Fig. 2 is the subregion synoptic diagram.

Fig. 3 is gray scale-lightness curve map.

Fig. 4 is the six color separation process flow diagram.

Five, embodiment

Below in conjunction with actual conditions the specific embodiment of the present invention is done detailed explanation.

Colorful picture six color separation printing method of the present invention as shown in Figure 1, concrete steps are as follows:

The first step: the digital picture that original copy is become RGB (RGB) color mode through scanning;

Second step: by color space conversion, promptly utilize image processing software photoshop to carry out the color mode conversion, the digital picture of RGB color mode is become the digital picture of CIELAB (a kind of color representation that International Commission on Illumination formulates) color mode;

The 3rd step: utilization six color separation algorithm resolves into yellow, magenta, cyan, black, orange and green six color separation version data with the digital picture of CIELAB color mode;

For digital picture original copy arbitrarily, finish the color separation process and must carry out (as shown in Figure 4) as follows, specifically:

1. carry out the Color Gamut Mapping conversion;

2. the color data of read pixel file one by one;

3. judge whether color is muted color, as the value (a of the red green axle of CIELAB color space coordinate ^*) with the value (b of champac axle ^*) equal simultaneously at 0 o'clock, be muted color, otherwise be not muted color, if muted color is then carried out gray scale-lightness curve, otherwise changeed next step;

4. calculate the hue angle of color;

5., and, then utilize black, pinkish red, its site number percent of orange subregion knob Jie fort (Neugebauer) Equation for Calculating, otherwise change next step less than the hue angle of orange printing ink if hue angle is more than or equal to the hue angle of magenta ink;

6., and, then utilize black, yellow, orange its site number percent of subregion knob Jie fort Equation for Calculating, otherwise change next step less than the hue angle of yellow ink if hue angle is more than or equal to the hue angle of orange printing ink;

7., and, then utilize black, yellow, green its site number percent of subregion knob Jie fort Equation for Calculating, otherwise change next step less than the hue angle of green oil China ink if hue angle is more than or equal to the hue angle of yellow ink;

8., and, then utilize black, green, blue or green its site number percent of subregion knob Jie fort Equation for Calculating, otherwise change next step less than the hue angle of blue or green printing ink if hue angle is more than or equal to the hue angle of green oil China ink;

9., or, then utilize black, pinkish red, blue or green its site number percent of subregion knob Jie fort Equation for Calculating less than the hue angle of magenta ink if hue angle is more than or equal to the hue angle of blue or green printing ink;

10. repeating step 2-9 disposes until all pixel datas;

11. recording disc gray scale color separation file.

After institute finished in steps, the color separation process was promptly finished.

In this 3rd step, the most important value that is six color separation algorithm and parameters.

Said six color separation algorithm, the value of its parameters is realized by following steps:

(1) regulation and control of neutral ash

Neutral grey composition in the image is independently generated by black print.

Make the black print signal strips, record lightness L value, can get lightness L and black print site number percent corresponding relation, as shown in Figure 3 with spectrophotometer or densitometer.Transverse axis is lightness L among the figure, and scope is from 0-100, and the longitudinal axis is gray scale (black print site number percent) K, and scope also is from 0-100, and by 5 samplings at interval, the described point line gets this figure.In the actual production process, lightness L value is the known quantity in the file, looks into required tusche amount can obtain brightness value and be L the time by Fig. 3 curve table is counter.

(2) partition boundaries and color of object subregion determines

Adopt blue or green (C), pinkish red (M), yellow (Y), black (K), orange (O), green (G) six primary colours, the position of each primary colours printing ink is drawn in LCH (brightness, chroma, hue angle) space, the line of their projections on C-H (chroma, hue angle) plane and true origin forms the subregion of a nature between any two, and each subregion is made of the delta-shaped region that black (K) and adjacent two color primaries surround.

If a target tinctorial pattern is arranged, the colors that it is all retouch out in LCH, and their projections on the C-H face then fall into corresponding subregion naturally so, specifically are the hue angle decision of which subregion by them.So, all colors all will fall into each subregion, and this color relation is synthesized by the primary colours of forming of its place subregion.As shown in Figure 2, random colour P has fallen into the subregion of being made up of black (K), pinkish red (M), blue or green (C), and color P is just synthesized as primary colours by M, C and K so.

Subregion is by the difference decision of the hue angle of adjacent two primary colours, therefore calculate the CIELAB value of primary colours printing ink by the conversion formula between CIEXYZ and the CIELAB (a kind of color representation that International Commission on Illumination formulates), utilize the hue angle computing formula to calculate its hue angle:

H _Ab=arctan (b ^*/ a ^*) formula (2)

A in the formula ^*The value of the red green axle of the expression CIELAB color space, b ^*The value of representative champac axle wherein.

Suppose two adjacent primary colours P ₁, P ₂Hue angle be respectively H ₁, H ₂(H ₁＜H ₂), the hue angle of aim colour is H _p, then formulate the following rules:

If the hue angle of color P is more than or equal to primary colours P ₁Hue angle H ₁, and less than primary colours P ₂Hue angle H ₂, then aim colour P drops on by primary colours P ₁, P ₂In the subregion of forming.

(3) utilization six color separation algorithm is as follows:

The six color separation algorithm adopts three look knob Jie fort equation methods of correction, be with traditional knob Jie fort equation difference, knob Jie fort primary colours in this equation no longer are blue or green (C), pinkish red (M), yellow (Y), but the primary colours of each subregion, whole colour gamut is divided into five subregions (subregion 1, subregion 2, subregion 3, subregion 4, subregion 5), and five groups of knob Jie fort primary colours (KMO, KOY, KYG, KGC, KCM) are therefore also just arranged.The title of subregion is to represent with the title of their primary colours printing ink, KMO represents that this subregion is made up of black ink, magenta ink and yellow ink, KOY represents that this subregion is made up of black ink, orange printing ink, yellow ink, KYG represents that this subregion is made up of black ink, yellow ink and green oil China ink, KGC represents that this subregion is made up of black ink, green oil China ink and blue or green printing ink, KCM represents that this subregion is made up of black ink, blue or green printing ink and magenta ink, and is as shown in table 1:

Table 1 subregion knob Jie fort primary colours

Subregion knob Jie fort equation is:

$\left\{\begin{array}{c}{X}^{1/n_x}=\underset{i=1}{\overset{16}{\mathrm{\Σ}}}{f}_i{X_i}^{1/n_x}\\ Y^{{1/n}_y}=\underset{i=1}{\overset{16}{\mathrm{\Σ}}}{f}_i{Y_i}^{1/n_y}\\ Z^{1/n_z}=\underset{i=1}{\overset{16}{\mathrm{\Σ}}}{f}_i{Z_i}^{{1/n}_z}\end{array}\right.$ Formula (1)

In the formula, n _x, n _y, n _zFor knob Jie fort correction factor, be followed successively by 2.7,2.65,2.5, X, Y, Z are the tristimulus values of aim colour, X _i, Y _i, Z _i, f _i(i=1 2......8) is respectively the tristimulus values and the corresponding dot area percentage of Essential colour unit, and the relation between the tristimulus values of Essential colour unit and the version dot area percentage of all kinds is provided by Demichel (Di Maike) relation.

With the KCM subregion is example, and each parameter item is provided by table 2, knob Jie fort correction factor n _x, n _y, n _z, its value is decided to be 2.7,2.65,2.5 respectively.

Table 2 KCM subregion Demichel relation table

Look unit	The look elemental area	The area symbol
			Black	k(1-c)(1-m)	f 1
Blue or green	(1-k)m(1-c)	f 2
			Product	(1-k)(1-m)c	f 3
Black, blue or green	kc(1-m)	f 4
			Black, product	k(1-c)m	f 5
Blue or green, product	(1-k)cm	f 6
			Black, blue or green, product	kcm	f 7
In vain	(1-k)(1-c)(1-m)	f 8

Paper is a 157g art paper, printing ink is Tianjin heavenly maiden's series ink, numbering is respectively: CT-425-1 is sky blue, CT-135-1 is pinkish red, yellow among the CT-236-1, CT-715-1 is black, CT-215-1 is orange and CT-315-1 is green, through subregion Essential colour unit tristimulus values that experiment records shown in table 3, table 4, table 5, table 6, table 7.

Table 3 KCM subregion Essential colour unit tristimulus values

	Blue or green	Black, blue or green	Black, blue or green, product	Black	Black, product	Product	Blue or green, product	In vain
									X	16.17	1.04	0.64	1.95	1.61	30.74	5.8	81.47
Y	23.01	1.45	0.88	1.96	1.12	15.77	3.56	85.72
									Z	64.20	2.37	0.59	1.68	1.30	21.16	16.89	97.05

Table 4 MKO subregion Essential colour unit tristimulus values

	Product	Product, black	Product, black, orange	Black	Black, orange	Orange	Orange, product	In vain
									X	30.74	1.61	2.87	1.95	2.78	49.32	27.11	81.47
Y	15.77	1.12	2.58	1.96	2.75	34.16	14.17	85.72
									Z	21.16	1.30	1.53	1.68	1.57	3.61	2.61	97.05

Table 5 OKY subregion Essential colour unit tristimulus values

	Orange	Black, orange	Black, orange, yellow	Black	Black, yellow	Yellow	Orange, yellow	In vain
									X	49.32	2.78	2.96	1.95	2.1	61.24	47.05	81.47
Y	34.16	2.75	2.85	1.96	2.46	68.46	32.8	85.72
									Z	3.61	1.57	1.38	1.68	1.48	6.38	1.56	97.05

Table 6 YKG subregion Essential colour unit tristimulus values

	Yellow	Black, yellow	Black, yellow, green	Black	Black, green	Green	Yellow, green	In vain
									X	61.24	2.1	0.75	1.95	0.67	11.86	8.89	81.47
Y	68.46	2.46	1.31	1.96	1.02	26.27	22.26	85.72
									Z	6.38	1.48	1.06	1.68	0.98	26.43	4.19	97.05

Table 7 GKC subregion Essential colour unit tristimulus values

	Green	Black, green	Black, green, blue or green	Black	Black, blue or green	Blue or green	Green, blue or green	In vain
									X	11.86	0.67	0.61	1.95	1.04	16.17	5.9	81.47
Y	26.27	1.02	1.03	1.96	1.45	23.01	14.28	85.72
									Z	26.43	0.98	1.33	1.68	2.37	64.20	23.21	97.05

At this is example with the KCM subregion still, and its knob Jie fort equation is:

$\left\{\begin{array}{c}{X}^{1/2.7}=k(1-c)(1-m)\·{1.95}^{1/2.7}+(1-k)m(1-c)\·{16.17}^{1/2.7}+(1-k)(1-m)c\·{30.74}^{1/2.7}+\mathrm{kc}(1-m)\·{1.04}^{1/2.7}\\ +k(1-c)m\·{1.61}^{1/2.7}+(1-k)\mathrm{cm}\·{5.8}^{1/2.7}+\mathrm{kcm}\·{0.64}^{1/2.7}+(1-k)(1-c)(1-m)\·{81.47}^{1/2.7}\\ Y^{1/2.65}=k(1-c)(1-m)\·{1.96}^{1/2.65}+(1-k)m(1-c)\·{23.01}^{1/2.65}+(1-k)(1-m)c\·{15.77}^{1/2.65}+\mathrm{kc}(1-m)\·{1.45}^{1/2.65}\\ +k(1-c)m\·{1.12}^{1/2.65}+(1-k)\mathrm{cm}\·{3.65}^{1/2.65}+\mathrm{kcm}\·{0.88}^{1/2.65}+(1-k)(1-c)(1-m)\·{85.72}^{1/2.65}\\ Z^{1/2.5}=k(1-c)(1-m)\·{1.68}^{1/2.5}+(1-k)m(1-c)\·{64.20}^{1/2.5}+(1-k)(1-m)c\·{21.16}^{1/2.5}+\mathrm{kc}(1-m)\·{2.37}^{1/2.5}\\ +k(1-c)m\·{1.30}^{1/2.5}+(1-k)\mathrm{cm}\·{16.89}^{1/2.5}+\mathrm{kcm}\·{0.59}^{1/2.5}+(1-k)(1-c)(1-m)\·{97.05}^{1/2.5}\end{array}\right.$

K in the formula, c, m represent the site number percent that black ink, blue or green printing ink and magenta ink are required respectively, separate this system of equations get final product the site number percent of required each printing ink of synthetic color of object.

Other four subregions (MKO, OKY, YKG, GKC) knob Jie fort equation is KCM subregion knob Jie fort equation roughly the same, no longer repeats.

The 4th the step: with above-mentioned six color separation version data through raster image processor (RIP) interpretation process;

The 5th step: export with the film setter am screening through the data after raster image processor (RIP) interpretation process, become the screening film, by the printer printing down, after making galley, become printed matter with press printing, or by direct platemaking machine am screening output, directly plate-making becomes printed matter by press printing.

Most important the determining of six look version site angles that be in this step.

Owing to adopt amplitude modulation site generation technique, the site angle of six look versions must be provided with by certain rule, under conventional color separation situation, six look versions cannot adopt the amplitude modulation site to carry out double exposure, because do not meet the requirement that cable angle staggers at least 15 degree, taboo " moire " in can occurring printing.But owing to used the six color separation method among the present invention, guaranteed at most only three kinds of colour superimpositions may occur at same position, and, in the middle of these three kinds of colors, (complementary colors is overlapping, obtains muted color complementary colors can not to occur, and in this six color separation method, muted color occurs with the black composition, so complementary colors can not occur simultaneously).Therefore, though be to have used six kinds of colors on the surface,, on specific to each position, be at most three kinds of colors and do not possess complementary colors.Drawn the rule that is provided with of following six look version screen angles thus:

Yellow, magenta, cyan, black four-color process net angle routinely are provided with, and orange net angle is identical with its complementary color cyan, and green net angle is identical with its complementary color magenta.List in table 3 at operable net angle.

Table 3 six look version net angles requirement (unit: degree) is set

The present invention adopts the mathematical model of setting up in the experiment to carry out color separation (but not look-up table), simultaneously, version of all kinds is when printing, adopt conventional amplitude modulation site, and needn't adopt frequency-modulation halftone dot, can be directly used in the printing of high-end elaboration living-article, under the situation that does not increase printing house production equipment and technological investment, utilize existing equipment and technical conditions, can realize the printing that six looks high-end elaboration is lived, print out inaccessiable printing effect under the conventional color separation printing technology method.Adopt this printing process, can make printing house when effectively utilizing existing printing resource with general technology strength, improve the quality of printed matter, also can participate in alive the production in the ranks of printing elaboration goes, improve the service level of whole press greatly, create the more output value, have broad application prospects, society and remarkable in economical benefits.

Claims (2)

1, a kind of colorful picture six color separation printing method is characterized in that, is realized by following steps:

The first step: the digital picture that Manuscript scanner is become the RGB pattern;

Second step: by color space conversion, promptly utilize image processing software photoshop to carry out the color mode conversion, the digital picture of RGB pattern is become the digital picture of CIELAB color mode;

The 3rd step: utilization six color separation algorithm resolves into yellow, magenta, cyan, black, orange and green six color separation version data with the digital picture of CIELAB color mode, and method is:

(1). carry out the Color Gamut Mapping conversion;

(2). individual element reads the color data of file;

(3). judge whether color is muted color, method is, when the value of the value of the red green axle of CIELAB color space coordinate and champac axle equals 0 simultaneously, be muted color, otherwise be not muted color, if muted color, by gray scale-lightness curve table, the anti-tusche amount that checks in, method is, make the black print signal strips, record lightness L value with spectrophotometer or densitometer, get lightness L and black print site number percent corresponding relation, lightness L, scope is from 0-100, gray scale is black print site number percent K, and scope also is from 0-100, looks into required tusche amount can obtain brightness value and be L the time by curve table is counter, if not muted color, change next step;

(4). calculate the hue angle of color;

(5) if. hue angle is more than or equal to the hue angle of magenta ink, and less than the hue angle of orange printing ink, then utilizes black, pinkish red, orange its site number percent of subregion knob Jie fort Equation for Calculating, otherwise change next step;

(6) if. hue angle is more than or equal to the hue angle of orange printing ink, and less than the hue angle of yellow ink, then utilizes black, yellow, orange its site number percent of subregion knob Jie fort Equation for Calculating, otherwise change next step;

(7) if. hue angle is more than or equal to the hue angle of yellow ink, and less than the hue angle of green oil China ink, then utilizes black, yellow, green its site number percent of subregion knob Jie fort Equation for Calculating, otherwise change next step;

(8) if. hue angle is more than or equal to the hue angle of green oil China ink, and less than the hue angle of blue or green printing ink, then utilizes black, green, blue or green its site number percent of subregion knob Jie fort Equation for Calculating, otherwise change next step;

(9) if. hue angle is more than or equal to the hue angle of blue or green printing ink, or less than the hue angle of magenta ink, then utilizes black, pinkish red, blue or green its site number percent of subregion knob Jie fort Equation for Calculating;

(10). repeating step 2-9 disposes until all pixel datas;

(11). by magnetic disc storage gray scale color separation file;

Said six color separation algorithm, be to adopt the method for revising three look knob Jie fort equations, knob Jie fort primary colours in this equation are primary colours of each subregion, whole colour gamut is divided into five subregions, KMO represents that this subregion is by black ink, magenta ink and yellow ink are formed, KOY represents that this subregion is by black ink, orange printing ink, yellow ink is formed, KYG represents that this subregion is by black ink, yellow ink and green oil China ink are formed, KGC represents that this subregion is by black ink, green oil China ink and blue or green printing ink are formed, KCM represents that this subregion is by black ink, blue or green printing ink and magenta ink are formed, and subregion knob Jie fort equation of five subregions is:

$\left\{\begin{array}{c}{X}^{1/n_x}=\underset{i=1}{\overset{8}{\mathrm{\Σ}}}{f}_i{X_i}^{1/n_x}\\ Y^{1/n_y}=\underset{i=1}{\overset{8}{\mathrm{\Σ}}}{f}_i{Y_i}^{1/n_y}\\ Z^{1/n_z}=\underset{i=1}{\overset{8}{\mathrm{\Σ}}}{f}_i{Z_i}^{1/n_z}\end{array}\right.$

In the formula, n _x, n _y, n _zFor knob Jie fort correction factor, be followed successively by 2.7,2.65,2.5, X, Y, Z are the tristimulus values of aim colour, X _i, Y _i, Z _i, f _i, i=1 wherein, 2......8 is respectively the tristimulus values and the corresponding dot area percentage of Essential colour unit, and the relation between the tristimulus values of Essential colour unit and the version dot area percentage of all kinds is provided by the Demichel relation;

The 4th the step: with above-mentioned six color separation version data through the raster image processor interpretation process;

The 5th step: with the output of film setter am screening, become the screening film, by the printer printing down through the data after the raster image processor explanation, after making galley, become printed matter, or directly export by the platemaking machine am screening with press printing, directly plate-making becomes printed matter by press printing; The screen angle of am screening output is provided with rule and is: yellow, magenta, cyan, black are provided with by four-color process net angle, and orange net angle is identical with its complementary color cyan, and green net angle is identical with its complementary color magenta, with black is the printed matter of dominant hue, and the net angle is set to yellow 0 degree, magenta 15 degree, cyan 75 degree, black 45 degree, orange 75 degree, green 15 or net angle are set to yellow 0 degree, magenta 75 degree, cyan 15 degree, black 45 degree, orange 15 degree, green 75 degree; With magenta, green is the printed matter of dominant hue, and the net angle is set to yellow 0 degree, magenta 45 degree, cyan 15 degree, black 75 degree, orange 15 degree, green 45 degree or net angle are set to yellow 0 degree, magenta 45 degree, cyan 75 degree, black 15 degree, orange 75 degree, green 45 degree; With cyan, orange be the printed matter of dominant hue, the net angle is set to yellow 0 degree, magenta 15 degree, cyan 45 degree, black 75 degree, orange 45 degree, green 15 degree or net angle are set to yellow 0 degree, magenta 75 degree, cyan 45 degree, black 15 degree, orange 45 degree, green 75 degree.

2, colorful picture six color separation printing method according to claim 1 is characterized in that, said six color separation algorithm, and definite method of its partition boundaries and color of object subregion is:

Adopt blue or green C, pinkish red M, yellow Y, black K, orange O, six primary colours of green G, the position of each primary colours printing ink is drawn in brightness, chroma, hue angle space, the projection on chroma, hue angle plane and the line of true origin form the subregion of a nature between any two, and each subregion is made of the delta-shaped region that black and adjacent two color primaries surround;

All colors are all retouched out in brightness, chroma, hue angle, their projections on chroma, form and aspect edged surface then fall into corresponding subregion naturally so, specifically be of the hue angle decision of which subregion by them, all colors all will fall into each subregion, and each color relation is synthesized by the primary colours of forming of its place subregion;

Subregion is by the difference decision of the hue angle of adjacent two primary colours, and its hue angle computing formula is as follows:

H _ab＝arctan(b ^*/a ^*)

A in the formula ^*The value of the red green axle of the expression CIELAB color space, b ^*The value of representative champac axle wherein.

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