JPH087737Y2 - Color separation auxiliary device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a color separation auxiliary device used in a color scanner for plate making, and in particular, a color separation system capable of always setting an appropriate color separation condition. A color separation aid used in combination with a conventional image processing device to build.

[Conventional technology]

As is well known, setting color separation conditions is an important task in plate-making color scanners and the like. The conventional plate-making color scanner is configured to manually set the color separation conditions.

Specifically, the density values of characteristic points such as highlight points and shadow points of a color original image are measured in advance, and each of yellow (Y), magenta (M), cyan (C) and black (K) is measured. The operator empirically determines what half-value value represents those feature points in each version. Then, the calculation characteristics of the color calculation unit of the scanner are adjusted using the color separation condition setting panel so that the feature points are color-separated into such a halftone color plate signal.

[Problems to be solved by the device]

Therefore, the proper color separation condition can be set only by a skilled operator, and it is difficult for an operator with low skill to set the proper color separation condition in the conventional scanner. Therefore, automation of setting of color separation conditions is desired.

On the other hand, when setting the color separation conditions, there are factors that are difficult to quantify in principle, such as the visual impression of the original image. Therefore, if it becomes possible to automate the setting of color separation conditions, if the operator is eliminated from the work of setting the color separation conditions by the automation, the color separation conditions will be standardized, and the appropriate color separation conditions will be set. There is also a problem that the original purpose cannot be achieved.

Further, since a plate-making scanner and the like are generally expensive, even if an automated system is provided, there is a cost problem for a user to obtain and use it. In other words, even though the color separation condition setting function is one of the important functions for the scanner, it is a great financial burden for the user to focus on only the color separation function and replace the currently used scanner with an automated system. Become.

[Purpose of device]

The present invention was made in response to the above circumstances, and the setting of color separation conditions can be executed without depending on the skill of the operator, and the operator can be involved in the setting process as necessary. Therefore, an object of the present invention is to reduce the financial burden on the user in constructing a color separation system that can always set appropriate color separation conditions.

[Means for solving the problem]

The concept of the construction of this invention is shown in FIG. That is, in this configuration, the color image input from the image input unit is color-separated by the color separation circuit coupled to the color separation condition manual setting unit, and the color-separated image signal obtained thereby is output as an image. The present invention is intended for a color separation assisting device used in combination with an image processing device for giving a predetermined image output to a means. The color separation assisting device includes (a) a signal inputting unit that is connectable to the image inputting unit and that inputs a density signal for each color component of the image transmitted from the image inputting unit; ) During prescanning of the image, the density signal is captured from the signal input means to statistically process the density distribution of each color component in the image, and based on the statistical processing, (C) The density conversion characteristic automatic determination means for automatically determining the density conversion characteristic; and (c) the density conversion characteristic is set, and the density signal is output when the main scanner of the image for performing the predetermined image processing on the image. (D) A signal output unit that is connectable to the density conversion circuit provided through the signal input unit and that is capable of being coupled to the color separation circuit and that outputs a converted signal from the density conversion circuit to the color separation circuit. Has a, by functional binding to the color separation circuit and the density conversion circuit via the signal output means, and can constitute a color separation unit of the image.

However, the "color separation circuit" in the image processing device is a circuit originally provided in the image processing device, and may be a color separation circuit used conventionally. And
When the color separation auxiliary device of the present invention is used with this image processing device, the color separation of the image is performed by the cooperation of this color separation circuit and the density conversion circuit in the color separation auxiliary device. Before using this combination, the image signal is generally supplied to the color separation circuit through the signal path shown by the broken line arrow in FIG. The route is not used. In other words, the image signal processing system in the color separation auxiliary device of this invention is
It is used by being inserted and connected between the image inputting means and the color separation circuit in the image processing apparatus.

It should be noted that the term "density" in the present invention is a general term that represents not only the optical density but also the signal level obtained by photoelectrically reading the density, the Munsell value, and other quantities that express the density of image gradation. Is a term.

[Action]

The color separation auxiliary device according to the configuration of the present invention is used in combination with an image processing device that does not have a color separation condition automatic setting function, and thus has a color separation condition automatic setting function and a manual correction function. The system can be built.

In this system, the color separation condition automatic setting is performed by this color separation auxiliary device. Since the color separation condition automatically set by this is performed through the statistical processing of the density distribution of each color component in the image to be color separated, it is an objective one that reflects the property of the image. Further, when the color separation condition automatically set in this way is desired to be more appropriate, the operator can correct the color separation condition by using the manual setting means in the image processing apparatus.

〔Example〕

A. Overall Structure and Schematic Operation FIG. 2 is an external view of a plate-making color scanner system 1 using a color separation assisting device according to an embodiment of the present invention. This system 1 is a color scanner body 100 for platemaking.
And the color separation auxiliary device 200 are electrically connected by the transmission cable 2. Of these, the scanner body
100 itself does not have an automatic setting function for color separation conditions,
As will be described later, it can be obtained by slightly modifying a conventionally used plate-making color scanner.

On the other hand, the color separation auxiliary device 200 is a device configured according to the present invention, and by adding the color separation auxiliary device 200 to the scanner body 100, it is possible to perform both automatic setting and manual correction of color separation conditions for the scanner system 1 as a whole. Become.
Below, I will explain.

(A-1) Scanner Main Body 100 The scanner main body 100 has an appearance configuration roughly divided into an input section 51 and an output section 52, and the input section 51 includes an original image drum 101 and a pickup head 104. Also, the output unit 5
The reference numeral 2 has a recording drum 131 and an exposure head 134, and the operation panel 125 of the scanner body 1 is provided on the input section 51 side.

FIG. 3 is a block diagram showing the internal configuration of the scanner body 100. Original drum 101 with color original 3 pasted
Is rotated in the α direction by the motor 103. Then, the pickup head 104 is translated in the β direction by a combination mechanism of the motor 107 and the feed screw 105. Pickup head
In photoelectrically reading the original image 3 by 104, the α rotation is for achieving main scanning, and the β-direction translation is for sub-scanning.

If the analog color density signals of blue (B), green (G) and red (R) of the color image read by the pickup head 104 are D _B , D _G and D _R , these color density signals D _B and D _G and D _R are three output terminals 141 via the signal line 151.
Will be led to each of the.

The color density signals D _B , D _G , and D _R are transmitted to the color separation auxiliary device 200 via the transmission cable 2, but the color separation auxiliary device 200
Then, these color density signals D _B , D _G , and D _R are used for two purposes. The first is the setting of color separation conditions, at which time the signal generated by the prescan of the original image 3 is set.
D _B , D _G , D _R are used. The second is transmission of the signals D _B , D _G , and D _R generated during the main scan for image recording to the color separation auxiliary device 200 for performing conversion thereof. Although the details of these operations will be described later, during the main scan, the analog color density signals D _NB , D _NG , and D _NR after being converted by the color separation auxiliary device 200 are transmitted by the transmission cable 2.
It is sent back to the scanner main body 100 via the and input to the three input terminals 14 inputs. Since both ends of the transmission cable 2 are coupling connectors, the cable 2 can be attached to and detached from the scanner body 100 and the color separation auxiliary device 200.

The color density signals D _NB , D _NG , and D _NR are transmitted via the signal line 152.
It is input to the color calculation circuit 121 composed of an analog computer. The color calculation circuit 121 is a circuit corresponding to the “color separation circuit” in FIG. 1, and after performing color calculation in the BGR system, converts the BGR color density into each color plate signal of YMCK. However, when the scanner main body 100 is used in combination with the color separation auxiliary device 200, the BGR color calculation in the color calculation circuit 121 may be omitted. This is because the color separation auxiliary device 200 performs conversion corresponding to BGR color calculation.

YMCK color plate signals are subjected to YMCK-based color calculations such as color correction and gradation conversion. Then, these signals after YMCK color calculation are transmitted to the halftone dot conversion circuit 122 via the signal line 153, and converted into YMCK halftone dot signals according to a predetermined screen pattern.

The YMCK halftone dot signals are combined in a time division manner and the exposure head 13
4 is applied to ON / OFF modulation of the recording laser beam from the exposure head 134. The exposure head 134 is translated in the β direction by a combination mechanism of a motor 137 and a feed screw 135.
On the other hand, the photosensitive film 4 for recording is wound around the recording drum 131 and rotated in the α direction by the motor 133. Then, by the combination of the main scanning by the rotation in the α direction and the sub scanning by the translation in the β direction, the exposure scanning by the recording laser beam is achieved, and the color plate image of YMCK is recorded on the photosensitive film 4. .

On the other hand, the rotation angles of the motors 103, 107, 133, 137 are detected by the rotary encoders 102, 106, 132, 136, respectively, and their rotation angle signals are given to the timing control circuit 124 via the signal lines 156, 157. The timing control circuit 124 generates a timing signal based on these rotation angle signals, and transmits this timing signal to the halftone dot conversion circuit 122 via the signal line 158. In addition, the motor control circuit 123 is connected to the timing control circuit 124 via the signal line 159.
Receive motor control timing signal from. Then, the motor drive signal generated by the motor control circuit 123 is transferred to the motors 103, 107, 13 via the signal lines 154, 155.
Given to 3,137.

The timing control circuit 124 also generates a main scanning gate clock Y _GATE , a sub scanning gate clock X _GATE and a sampling clock CLK, and outputs these clocks to the output terminals 143, 144 and 145. The generation timing of these clocks is shown in FIG. 15 (described later). The main scanning gate clock Y _GATE indicates the effective area width of the original image 3 in the main scanning direction, and the sub scanning gate clock X _GATE is. Specifies the effective area width of the original image 3 in the sub-scanning direction. Also,
The sampling clock CLK is used when the pixel is sampled in the color separation auxiliary device 200. Therefore, these clocks Y _GATE , X _GATE , and CLK are transmitted to the color separation auxiliary device 200 via the transmission cable 2.

The operation panel 125 of the scanner body 100 is connected to the color calculation circuit 121 and the halftone dot conversion circuit 122 via a signal line 160. The color calculation circuit 121 is provided with an adjustment knob 126 for manually adjusting the color calculation characteristic in the BGR system and the color calculation characteristic of each YMCK color plate component. The adjusting knob 126 can be used for setting and correcting the color separation conditions such as the above-mentioned calculation characteristics, and thus corresponds to the "manual setting means" in the configuration of the present invention. Also, the halftone conversion circuit 122
Display that displays the dot% value of each color plate signal converted by dot
127 is also provided on this operation panel 125.

It should be noted that in a normal color scanner, the pickup head
The output of 104 is given to the color calculation circuit 121 via the signal line 110.
When diverting as 100, this signal line 110 is removed. Further, the signal line 110 may be turned off by a switch.

(A-2) Color Separation Auxiliary Device 200 FIG. 4 is a block diagram showing the internal structure of the color separation auxiliary device 200. The color density signal input via the input terminal 201 and the signal line 206 is converted into a digital signal by the A / D converter 207. The digital color density signal obtained thereby is sent to the image memory for each of the B, G, and R color components via the signal line 220.
221-223 and stored in these image memories 221-223. However, this storing operation is performed only when the original image 3 is pre-scanned.

The image memories 221 to 223 are connected to the CPU 231 via the bus 236. The CPU 231 is also connected to the program memory 232 and operates according to the program stored in this memory 232. Further, the color separation assisting device 200 is provided with an operation panel 233 and a CRT 235. Of these, the CRT 235 is used when displaying the images stored in the image memories 221-223 and checking the contents thereof. Many of the electrical components of the color separation auxiliary device 200 are provided in the housing box 61 shown in FIG.
The operation panel 233 is placed on the storage box 61. The operation panel 233 has a keyboard 234.

As will be described later, the CPU 231 has a function of automatically setting color separation conditions based on the color density data in the image memories 221-223. The color separation conditions are loaded in the look-up table memories (LUT) 208 to 210 corresponding to the respective color components of B, G and R in the form of a color density value conversion table.

During the main scan for recording an image, the B, G, R color density values output from the A / D converter 207 are taken into the LUTs 208 to 210 and converted by the conversion table. Then, it becomes an analog color density signal by the A / D converter 210 and is converted to the output terminal 202 via the signal line 211 to the converted signals D _NB , D
It is output as _NG and D _NR .

That is, the color separation assisting device 200 not only functions as a setup device that determines the conversion characteristics of the LUTs 208 to 210, but also performs the main scan, the color operation circuit of FIG.
The color separation process itself is also performed in cooperation with 121.

On the other hand, the clock signals Y _GATE , Y _GATE , and CLK input from the input terminals 203 to 205 are given to the timing control circuit 228. The timing control circuit 228 generates a control timing signal based on these clock signals, and the A / D converter 207, the LUTs 208 to 210, and the D / A converter 21 via the signal line 229.
0, this control timing signal is given to the image memories 221-223.

B. Details of Operation of System 1 FIG. 5 is a flowchart showing the operation of the scanner system 1. Of the steps shown in this flowchart, the routine RT1 surrounded by the one-dot chain line is an automatic setting routine for color separation conditions. The first routine RT2 in this routine RT1 is a highlight side reference density value and a shadow side when converting the density range of the BGR color density value in the original image 3 into a density range (normalized density range) suitable for image recording. It is for determining the reference density value. In other words, the positions of both ends of the conversion curve for normalization conversion (normalization curve) are specified on the conversion coordinate plane by this routine RT2.

The next routine RT3 is a routine for determining the shape of the normalized curve. For example, it is determined whether the curve is convex upward, downward convex, or straight on the transformation coordinate plane. It The determination of the curve shape has a meaning as preparation for tone correction for each BGR color component.

The step S6 after this routine RT3 is the routine RT2, R
This is the step of identifying the normalization curve based on the conditions determined by T3, and the above is the entire process of automatically setting the color separation conditions.

Thereafter, the color separation condition correction (step S7) is performed based on the manual operation to complete the setup, and the main scan (step S8) for image recording is executed. Below, I will explain.

(B-1) Density range correction preparation routine RT2 First, in step S1 in FIG. 5, the entire copy target portion of the original image 1 is prescanned. Then, the analog color density signals D _B , D _G , and D _R are transmitted to the color separation auxiliary device 200, and A
After forming digital signals for each pixel according to the sampling pitch of / D conversion, these are stored in the image memories 221 to 223. Hereinafter, the values of the color densities indicated by these signals D _B , D _G , and D _R will be represented by the same symbols D _B , D _G , and D _R. Also, original picture 3
When the size is large, this storage operation of the color density values D _B , D _G , and D _R is executed while thinning out the pixels. Note that FIG. 6 shows the relationship of information usage in the subsequent processes. However, S1 and S added to each block
101, ... Correspond to the step numbers in FIG.

In the next step S100, these color density values D _B , D _G , and D _R are read from the image memories 221-223, and from these, highlight side average color density values D _HAB , D _HAG , D _HAR , and shadow side average color. This is a subroutine for _obtaining the density values D _SAB , D _SAG , and D _SAR . This subroutine is described in detail in Japanese Patent Application No. 63-312684 previously filed by the applicant of the present invention, but only an outline thereof will be described here.

In FIG. 7 showing the details of step S100, in the first step S101, the density value D _B obtained in step S1,
The average density value for each pixel is calculated from D _G and D _R : D _M = (D _B + D _G + D _R ) / 3. Further, this calculation is performed for all the pre-scanned pixels, and the class indicating the range of the average density value D _M is set on the horizontal axis and the number of pixels N _p is set on the vertical axis, and the average density value frequency histogram is obtained as shown in FIG. To create. In FIG. 8, the median of the classes is indicated by D _Mi (i = 1 to n).

In step S102, for each class of the average density value frequency histogram, each color component B, G, R of each pixel included in the histogram
The density values D _B , D _G , and D _{R for each} are cumulatively added. This process is performed independently for each class. After further performing this calculation, each class value D _Mi (i = 1 to n) is set on the horizontal axis, and the cumulative density values ΣD _B , ΣD _G , ΣD _R corresponding to the pixels included in each class are set on the vertical axis. , A cumulative density value histogram is created for each color component. FIG. 9 shows an example of this cumulative density value histogram, and such a cumulative density value histogram is obtained for each of X = B, G, and R.

As an example, class value D _Mi = 1.0, class width 0.1 (0.95
≦ D _M <1.05) will be described. The number of pixels included in this class is set to 3 for convenience, and the density data of each pixel is pixel 1: D _B = 1.10, D _G = 0.90 D _R = 0.95 (D _M ≈0.98) Pixel 2: D _B ＝ 1.00, D _G = 1.10 D _R = 0.90 (D _M ≈1.00) Pixel 3: D _B = 1.00, D _G = 0.95 D _R = 0.95 (D _M ≈0.97)

When the cumulative density value histogram shown in FIG. 9 is X = B, the cumulative density value ΣD _B in that class (0.95 ≦ D _M <1.05) is ΣD _B = 1.10 + 1.00 + 1.00 = 3.10. Similarly, the other cumulative density values ΣD _G and ΣD _R are also ΣD _G = 0.90 + 1.10 + 0.95 = 2.95 ΣD _R = 0.95 + 0.90 + 0.95 = 2.80.

Such processing is performed for each class, and each color component B, G,
Complete each cumulative density histogram for each R. (6th
See also the block of step S102 in the figure. Incidentally, in FIG. 6, each histogram is approximately drawn by a curve. ) In step S103, from the average density value frequency histogram shown in FIG. 8, the relative frequency RN (%) of the pixels cumulatively added from the lower density is plotted on the horizontal axis of the class value D _Mi (i = 1 to n). The cumulative relative frequency histogram as shown in FIG. 10 is created on the vertical axis. The histogram has a shape that changes from 0% to 100% within the range of the minimum and maximum generated density values D _Mmin and D _Mmax . However, in FIG. 10, this cumulative relative frequency histogram is approximated by a curve within the range that the class width is sufficiently small.

In the next step S104, a predetermined cumulative density appearance rate
RN _H and RN _S are applied to the cumulative relative frequency histogram shown in FIG. 10 to obtain the temporary highlight average density value D _MH and shadow average density value D _MS , respectively. The values of the cumulative density appearance rates RN _H and RN _S are values obtained in advance by analysis of a large number of sample original images to give statistically optimum highlight points and shadow points, for example, 1%, The value is about 98%.

In step S105, of the cumulative density value histograms for each color represented in FIG. 9, as shown by the hatched lines in FIG. 11, the highlight side has a provisional highlight average density value D _MH or less. Area (D _Mmin ≤ D _M ≤ D _MH ), and for the shadow side, pay attention to the area (D _MS ≤ D _M ≤ D _Mmax ) above the provisional shadow average density value D _MS , and accumulate within that range. The pixel values of the density values ΣD _B , ΣD _G , and ΣD _R are averaged for each color component.

That is, if the pixel average on the highlight side is written as <...> _H and the pixel average on the shadow side is written as <...> _S , the highlight side average color density value D obtained by this pixel average is written.
_HAB , D _HAG , D _HAR and shadow side average color density value D _SAB ,
D _SAG and D _SAR are D _HAX = <ΣD _X > _H (X = B, G, R) (1) D _SAX = <ΣD _X > _S (X = B, G, R) (2) Is.

For example, X in FIG. 11 is B, and the temporary highlight density
When D _MH is D _M5 , D _HAB = (D _M1 + D _M2 + D _M3 + D _M4 + D _M5 ) / (N _P1 + N _P2 + N _P3
+ N _P4 + N _P5 ) (3) However, N _Pi (i = 1 to 5) is the average density value D _M
Is the number of pixels belonging to the class D _Mi , and is obtained from the histogram in FIG.

In this way, the average color density values D _HAX and D _SAX on the highlight side and the shadow side for each color component shown in the center of FIG.
(X = B, G, R) is obtained. With the above, the subroutine corresponding to step S100 is completed, and the process returns to the main routine of FIG.

In step S2 of FIG. 5, the average color density values D _HAX and D _SAX thus obtained are used to highlight the density value D _HX.
And the shadow density value D _SX (X = B, G, R). For example, D _HX = D _HO + K _H (D _HAX −D _HO ) ... (4) D _SX = D _HO + K _S (D _SAX −D _SO … (5) D _HO = MIN (D _HAB , D _HAG , D _HAR ) (6) D _SO = MAX (D _SAB , D _SAG , D _SAR ) ... D _HX , D _SX (X = B, G, R) can be determined according to the equation (7), where MIN ( …) And MAX (...) are operations for obtaining the minimum value and the maximum value, respectively, and K _H and K _S are constants.

(B-2) Tone correction preparation routine RT3 The principle of the routine RT3 is described in Japanese Patent Application No. 63-165365 previously filed by the applicant of the present invention.
The outline of the routine RT3 according to this principle will be described below. Note that the information usage relationship in this routine RT3 is shown in FIG.

First, in step S3 of FIG. 5, the density range ΔD of the original image 3 is calculated by the following equation (8) (FIG. 12 (c)).

ΔD = D _SO −D _HO (8) However, D _SO and D _HO are values calculated by the equations (6) and (7) described above.

The concentration range ΔD may be defined by using ΔD = D _Mmax −D _Mmin (8a) instead of the equation (8).

In the next step S4, a combination ratio f (ΔD) for curve combination described later is set according to the value of the density range ΔD.
Find the value of. FIG. 12 (d) shows a function form for obtaining the composite ratio f (ΔD) from the density range ΔD. However, ΔD ₁ and ΔD ₂ are predetermined threshold values, and f _max is a predetermined maximum value. Further, ΔD _C is a value of ΔD such that f (ΔD) = 1 (9).

Next, two predetermined standard curves F
₁ (D) and F ₂ (D) are combined using this combination ratio f (ΔD) to obtain a combined curve K (D) (step S6).
Examples of these standard curves F ₁ (D) and F ₂ (D) are shown in FIGS. 12 (a) and 12 (b). In this example, F ₁ (D)
Is an upwardly convex curve, while F ₂ (D) is a straight line. However, D _max is the upper limit value of the range of the density variable D before conversion, and Max is the upper limit value of the density variable D _N after conversion. Further, as a synthetic expression of the standard curves F ₁ (D) and F ₂ (D), for example, K (D) = {1-f (ΔD)} F ₁ (D) + f (ΔD) F ₂
(D) ... (10) can be used.

An example of the combined curve K (D) is shown in FIG. 12 (e). As can be seen from FIGS. 12 (a), (b), (d) and (10), the curve K (D) when the concentration range ΔD is larger than the threshold value ΔD _C is a curve convex upward (for example, K ₁ (D)), and the curve K (D) when it is smaller than the threshold ΔD _C becomes a downward convex curve (for example, K ₃ (D)). When ΔD = ΔD _C , the straight line K ₂ (D) becomes the combined curve K (D).

As will be described later, such a curved state of the synthesized curve K (D) is reflected in the shape of the normalized curve.

(B-3) Determination of Normalized Curve In step S6 of FIG. 5, the normal density for each color component is calculated using the reference density values D _HX and D _SX determined by the routine RT2 and the above-mentioned synthesized curve K (D). Of the generalized curve G _X (D _X ) with X = B, G,
Make a decision for each R. That is, with respect to the predetermined density value D _NSX determined near the upper limit value of the image recording density range for each color component and the density value D _NHX set near the lower limit value, two points on the density conversion coordinate plane are set. : P _SX = (D _SX , D _NSX ) ... (11) P _HX = (D _HX , D _NHX ) ... (12) is defined (Fig. 12 (f)). Then, the curve X (D) is modified so as to pass through the two points P _SX and P _HX , thereby determining the normalized curve G _X (D). Therefore, the synthesized curve K
(D) is common to X = B, G, and R, but the normalized curve G
_X (D) is determined separately for each of X = B, G, R.

FIG. 13 is a diagram conceptually expressing the above process. The reference concentration values D _SX , D according to the routine RT2 in FIG.
_{Since HX} is determined, the 13th equation is obtained via equations (11) and (12).
The points P _SX and P _HX in the first quadrant I of the figure are determined, and the straight line RC specified accordingly becomes the conversion characteristic for correcting the density range.

On the other hand, the tone correction curve TC in the second quadrant II is
This corresponds to the combined curve K (D) in FIG. That is, the curve TC has significant information only in its curved state, and the positions at both ends thereof are fixed.

In the third quadrant III, the coordinate axis d ₂ is D by the straight line D _NX = d _2.
It is a quadrant that _moves to _NX and has no physical meaning.
The normalized curve G _X (D _X ) corresponding to the combination of the conversion characteristic by the straight line RC and the conversion characteristic by the curve TC is the fourth quadrant.
Given within IV. The normalized curve G _X (D _X ) gives the density range correction characteristic by the positions of both ends thereof and the tone correction characteristic by the curved state thereof.

The normalized curve G _X (D _X ) thus identified is CPU2
A numerical table is created by 31 and the LUTs 208 to 210 in FIG.
The color components X = B, G, and R are loaded. Then, this completes the automatic setup in the color separation assisting device 200.

(B-4) Manual correction of color separation conditions On the other hand, the color calculation circuit 121 (FIG. 3) in the scanner main body 100
For, the provisional color separation condition is set based on the manual operation of the adjustment knob 126. Color operation circuit 121 is a function of performing both the color calculation of a color arithmetic and YMCK system BGR systems, such as the output D _NX input D _NX for the former
The linear characteristic such as is given, and the standard calculation characteristic is given to the latter. This manual setup is temporary and does not require a high degree of skill.

Next, the operator sets the pickup head 104 to the original image 3
Of the color density signal D _NX (X = B, G, R) for that point is transmitted to the color separation auxiliary device 200. Then, these color density signals D _NX are converted by the LUTs 208 to 210 to become D _NX (X = B, G, R), and return to the scanner body 100.

This signal D _NX undergoes color calculation in the color calculation circuit 121,
It is given to the halftone dot conversion circuit 122. The output of the halftone dot conversion circuit 122 at this time is displayed on the display 127 as a halftone dot value for each color of YMCK. The operator operates the adjustment knob 126 so that the value displayed on the display 127 becomes a desired value, and thereby corrects the calculation characteristic (that is, the color separation condition) in the color calculation circuit 121. This correction is for the color calculation circuit
One or both of the BGR color calculation characteristic and the YMCK color calculation characteristic in 121 can be performed. For example, such manual correction includes correction of color correction characteristics and gradation conversion characteristics in YMCK system. Then, by this correction operation, LUT208 ~ 21
The color separation condition expressed by the combination of the respective functions of 0 and the color calculation circuit 121 is corrected. That is,
In this embodiment, the target of auto-setup is the conversion characteristic in the LUTs 208 to 210, and the target of manual correction is the calculation characteristic in the color calculation circuit 121.
From the perspective of the color separation process as a whole, the color separation conditions obtained through automatic setting have been corrected through manual operation. This correction work corresponds to step S7 in FIG.

Then, when the entire setup process is completed in this way, the main scan in step S8 is performed. This main scan itself has already been described, but LUT208
The appropriate YMCK color separation image can be obtained on the film 4 according to the appropriate color separation conditions set in 210 to 210 and the color calculation circuit 121.

By the way, it is important that the above-mentioned manual correction of the color separation conditions has a high work efficiency as compared with the case where all the color separation condition settings are manually performed. That is,
Since the color separation conditions obtained through the auto setup always have a certain degree of appropriateness, a high degree of color separation conditions can be obtained with only a slight manual correction.
Further, even when an operator with a low degree of skill operates the scanner system, it is possible to easily set appropriate color separation conditions because the automatic setup function can be used.

C. Signal acquisition timing for automatic setup FIG. 14 shows the color density signal which is the basis for the above-mentioned automatic setup operation in the color separation auxiliary device 200.
It is a flowchart which shows the capture processing of D _B , D _G , and D _R.
First, in step S201, the start switch (not shown)
When turned on, the timing control circuit 12 is initialized (step S202). Then, the clock signals CLK, Y _GATE , and X _GATE transmitted from the scanner body 100 are taken into the timing control circuit 228.

The scanning gate clocks Y _GATE and X _GATE are both signals that are activated at "L", and wait in step S203 until the sub-scanning gate clock X _GATE becomes "L". When the prescan of the original image 3 enters the effective area of the original image 3 in the sub-scanning direction,
Clock gate X _GATE becomes “L”. Further, the main scanning gate clock Y _GATE becomes “L” only while scanning the effective area of the original image 3 in the main scanning direction, and during that period, sampling of the signals D _B , D _G , and D _R and image memory are performed. 221-2
The data is stored in 23 (steps S204, S205). This capturing period is one of the periods (for example, PR ₀ ) indicated by parallel hatching in FIG. 15, and sampling for each pixel is performed according to the sampling clock CLK.

When sampling for one scanning line is completed, the sub-scanning gate clock X _GATE is referenced again, and this clock X _GATE is set to “L”.
If so, the process returns to step S204, and sampling for the next scan line is executed within the period PR ₁ .

In this manner, sampling for one scanning line is performed in each period PR corresponding to one rotation of the original image drum 101, and sampling is completed when X _GATE = “H”. Then, after that, each step of the auto-setup processing described above is executed.

In this way, the clock signals X _GATE , Y _GATE , and CLK transmitted from the scanner body 100 are used to synchronize the operations of the scanner body 100 and the color separation auxiliary device 200.

D. Other Embodiments [1] FIG. 16 is a block diagram of a color separation auxiliary device 400 which is another embodiment of the present invention. This device 400 is used when the color calculation circuit of the scanner body is a digital circuit. Therefore, the configuration of the scanner body will be briefly described before the description of FIG.

FIG. 17 is a partial block diagram of the scanner main body 300 including the digital color calculation circuit 305. This scanner body 300
Includes an A / D converter 301 that converts an analog color density signal from the pickup head 104 into a digital signal. When the scanner main body 300 is used alone, the output of the A / D converter 301 is given to the digital color calculation circuit 305 via the signal line 303.

When the scanner main body 300 is used in combination with the color separation auxiliary device 400, the signal line 303 is removed and the A / D
The output of the converter 301 is output via the signal line 302 to the output terminal 141.
Is given to. Further, the input terminal 142 and the color calculation circuit 305 are connected by the signal line 304. The color calculation circuit 3
In order to control the operation timing of 05, the timing control circuit 124 supplies a clock signal to the color calculation circuit 305. The rest of the configuration of the scanner body 300 is the same as that of the scanner body 100 of FIG. 3 except that a halftone conversion circuit (not shown) is configured to operate with respect to an analog input. .

Corresponding to the configuration of the scanner main body 300 in this way, in the color separation auxiliary device 400 of FIG. 16, the input terminal 2
01 is LUT208-210 and image memory without going through A / D converter
221-223 and connected. The outputs of the LUTs 208 to 210 are given to the output terminal 202 without passing through the D / A converter. The rest of the structure is substantially the same as that of the color separation assisting device 200 of FIG.

Therefore, the digital color density signals D _B , D _G , and D _R obtained in the scanner body 300 are transmitted to the color separation auxiliary device 400 via the transmission cable 2 and given to the LUTs 208 to 210 as they are. Then, the digital outputs D _NB , D of the LUTs 208 to 210
_NG and D _NR are sent back to the scanner body 300 via the transmission cable 2. The method of determining the normalization curve to be loaded into the LUTs 208 to 210 is the same as that of the color separation auxiliary device 200 in FIG.

[2] In the above two embodiments, the manual correction of the conversion cables automatically set in the LUTs 208 to 210 is not performed. However, an adjustment knob is provided on the color separation auxiliary device, and the LUT208-
A circuit for modifying the table contents in 210 may be provided in the color separation auxiliary device. It is also possible to display the table contents in the LUTs 208 to 210 on the CRT 235 in the form of curves or numerical values.

[3] It is also possible to incorporate the circuit in the color separation auxiliary device 200 or 400 into the scanner main body 100 or 300. It is also possible to use an analog calculator instead of the LUTs 208 to 210.

Furthermore, this invention is not limited to plate-making color scanners,
It is also applicable to other color image processing systems that perform color separation.

[Effect of device]

As described above, the color separation auxiliary device according to the configuration of the present invention, when combined with an image processing device that does not have a color separation condition automatic setting function, has both a color separation condition automatic setting function and a manual correction function. It is possible to build a system that has.

Therefore, an appropriate color separation condition can be set without depending on the skill of the operator, and the operator can correct the color separation condition as necessary, thereby further improving the color separation condition.

Furthermore, by combining with the color separation auxiliary device according to the configuration of the present invention, it is possible for the user to improve the performance while using the image processing device on hand, and the economic burden on the user is reduced.

[Brief description of drawings]

FIG. 1 is a block diagram corresponding to the configuration of the present invention, FIG. 2 is an external perspective view of a plate-making color scanner system which is an embodiment of the present invention, and FIG. 3 is a scanner having an analog color arithmetic circuit. FIG. 4 is a block diagram of the main body, FIG. 4 is a block diagram of a color separation auxiliary device that can be used in combination with the scanner main body of FIG. 3, FIG. 5 is a flowchart showing the overall operation of the embodiment, and FIG. , An explanatory view showing a process of determining a reference density value of an original image as a use relationship of information, FIG. 7 is a flowchart showing a reference density value determination routine, FIG. 8 is a view showing an average density value frequency histogram, FIG. FIG. 9 is a diagram showing a cumulative density histogram for each color component, FIG. 10 is a diagram showing a cumulative relative frequency histogram, and FIG. 11 is a process for calculating an average density value from a part of the histogram in FIG. of FIG. 12 is an explanatory diagram showing the relationship of use of information in the process of determining the curve shape for tone correction, and FIG. 13 is a conceptual illustration of density range correction and tone correction. FIG. 14 is a flow chart showing the signal acquisition operation in the color separation auxiliary device, FIG. 15 is a timing chart showing the signal acquisition timing in the color separation auxiliary device, and FIG. 16 is a scanner equipped with a digital color arithmetic circuit. FIG. 17 is a block diagram showing a color separation auxiliary device that can be used in combination with the main body, and FIG. 17 is a partial block diagram of a scanner including a digital color arithmetic circuit. 1 ... prepress color scanner system, 2 ... transmission cable, 100, 300 ... scanner, 200, 400 ... color separation assist _{device, D B, D G, D} R ... color density _{signals, D NB, D NG, N} NR ... normalization transform Color density signal already used, D _HK ... Highlight density value, D _SK ... Shadow density value, G _X (D) ... Normalized curve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display H04N 1/04 D

Claims (1)

[Scope of utility model registration request] 1. A color image input from image input means is color-separated by a color separation circuit coupled to a manual setting means for color separation conditions, and the color-separated image signal obtained thereby is sent to image output means. A color separation auxiliary device used in combination with an image processing device for giving a predetermined image output, comprising: (a) the image which can be coupled to the image input means and which is transmitted from the image input means. Signal input means for inputting a density signal for each color component, and (b) the density signal for each color component in the image is statistically acquired by taking in the density signal from the signal input means during prescanning of the image. A density conversion characteristic automatic determining means for processing and automatically determining a density conversion characteristic for each color component of the image based on the statistical processing; The density conversion circuit, to which the density signal is applied via the signal input means during the main scan of the image for performing the predetermined image processing, and (d) the color separation circuit, which can be combined with the density conversion circuit. Signal output means for outputting a converted signal from the circuit to the color separation circuit, and the color separation means for the image by the functional connection between the density conversion circuit and the color separation circuit via the signal output means. A color separation assisting device, which is capable of being configured.