JPH10200749A - Method of creating gradation correction curve and image output device - Google Patents

Abstract

(57) Abstract: A so-called output device condition, for example, when the beam diameter of a laser beam to be exposed and recorded on a film master coated with a photosensitive material is changed or when γ of the photosensitive material is changed. Is changed, a tone correction curve corresponding to a new output device condition is simply created. Kind Code: A1 A tone curve is created in advance under standard conditions, for example, a beam diameter is a standard size, and γ of a photosensitive material is a standard value, and when an output condition of the output device is changed, a test pattern is generated. From the generation unit 24, the dot area ratio is 0 to
A test pattern in a flat screen of 10%, 45% to 55%, and 90% to 100% is output to obtain a test pattern film Ft. A measuring device 36 such as a densitometer measures a point where a density appears, a point where a tone jump occurs, and a point where the density is not added, and based on these measurement points, corresponds to a new output device condition based on a reference tone curve. Obtain a desired gradation correction curve.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing scanner for outputting a film on which a dot image is formed, and a CTP (Computer T) for outputting a printing plate on which a dot image is formed.
o) A method for creating a gradation correction curve for gradation conversion in an image output device such as a color printer or a small-number printing device that outputs a hard copy on which a density gradation image is formed, and the gradation correction curve. The present invention relates to an image output device that is created and used.

[0002]

2. Description of the Related Art An image output device is used to obtain a film on which a halftone image is formed. The image output device includes, for example, a scanner, an image data processing computer connected to the scanner, a raster image processor connected to the image data processing computer, and an image setter connected to the raster image processor. And a film processor connected to the imagesetter.

In an image output apparatus having such a configuration, image data read from an image document by a scanner or the like is subjected to gradation conversion based on a gradation correction curve by a computer for image data processing, and a raster image The processor converts the gradation-converted image data into binary image data by comparing the image data with a threshold matrix, and the image setter lays out the binary image on a film master coated with a photosensitive material based on the binary image data. The film is exposed and recorded as an image, and the film master on which the binary image is exposed and recorded by the film processor is developed to obtain a film on which a halftone dot image is formed.

Usually, the computer for image data processing and the raster image processor are closely provided for processing, and are often provided as an integrated product. Less than,
In this specification, for the sake of simplicity, it is assumed that this integrated product is called a raster image processor, and that a gradation correction curve is stored in the raster image processor.

[0005]

By the way, the gradation correction curve is based on the specifications relating to recording such as the beam diameter and laser power of the laser beam in the image setter and the γ characteristics (density characteristics with respect to the exposure amount) of the photosensitive material. It is preferable that the characteristic curve corresponds to the image output conditions such as the above. This is because it is desired that the output gradation changes smoothly with respect to the input gradation and that there is no tone jump.

However, for example, in the case of a general-purpose raster image processor in which a plurality of different types of image setters are connected to the output side, a gradation correction curve corresponding to all image output conditions is not always obtained. However, even if it is obtained, it is necessary to accumulate a large amount of data, and there is a problem that management is complicated and cost is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and a method of creating a gradation correction curve which can easily create a gradation correction curve corresponding to a new image output condition. And an image output device.

[0008]

SUMMARY OF THE INVENTION The present invention is a reference in a method of creating a gradation correction curve for converting input gradation image data into gradation image data corresponding to image output conditions. When a tone curve serving as a reference obtained in advance under image output conditions is prepared, and when the input gradation image data is to be subjected to gradation conversion under a new image output condition, the gradation curve is converted under the new image output condition. And outputting a tone correction curve for a new image output condition based on the reference tone curve based on information obtained from the test pattern.

According to the present invention, when a tone correction curve corresponding to a new image output condition is to be created, a test pattern is output under the new image output condition, and the test pattern is obtained from the test pattern. Since a tone correction curve for a new image output condition based on a reference tone curve is created based on the information, a tone correction curve suitable for the new image output condition can be easily created. Can be.

In this case, if the test pattern is a test pattern including a starting point of a halftone dot on the highlight side, a contact point of the halftone dot, and a starting point of a halftone dot on the shadow side, a new image output The information obtained from the test pattern output according to the conditions is the density at the beginning of the halftone dot, the density before and after the contact portion of the halftone dot, and the density at the beginning of the halftone dot dropout. The tone curve serving as a reference can be converted by, for example, a mathematical function conversion process, and a tone correction curve for a new image output condition can be created by an arithmetic process.

The accuracy of the obtained gradation correction curve can be determined by setting the reference image output condition to a condition in which the output device and the photosensitive material have substantially medium characteristics. The error is a value obtained by assigning the error to the positive or negative value with respect to the maximum change in the material property, and in a normal case, it is possible to generate a stochastically accurate gradation correction curve.

Further, according to the present invention, after the input gradation image data is subjected to gradation conversion using a gradation correction curve, a threshold matrix is actuated, binarized, and converted into binary image data.
After exposing and recording the photosensitive material with the binary image data,
In an image output apparatus for obtaining a film on which a halftone dot image is formed by developing, a standard photosensitive material, a standard light beam for exposing and recording a sheet carrying the standard photosensitive material, and an exposure A reference tone curve storage unit for storing a reference tone curve obtained under standard output conditions comprising standard development conditions for developing the recorded sheet, and when the contents of the standard output conditions change, A tone correction curve for outputting a test pattern under various output conditions and creating a tone correction curve for a new image output condition based on the reference tone curve based on information obtained from the test pattern. And a creating unit.

According to the present invention, when a tone correction curve corresponding to a new image output condition is to be created, the tone correction curve creating section outputs a test pattern under the new image output condition. Since a tone correction curve for a new image output condition based on the reference tone curve is created based on the information obtained from the test pattern, the tone matching the new image output condition A correction curve can be easily created.

[0014]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a basic configuration of an image output system 10 according to this embodiment. The image output system 10 has a gradation correction curve setting unit 12 which is a lookup table. The gradation correction curve setting unit 12 includes a gradation correction curve created by a gradation correction curve The reference gradation correction curve is set as a look-up table. Instead of a lookup table, a function conversion unit may be used.

The tone correction curve setting unit 12 has an input terminal 1
6, gradation image data (also referred to as multi-value image data, gradation image signal, and multi-value image signal) G having an n-bit resolution is input as dot% data. Note that the gradation image data G
Are, for example, C (cyan), M (magenta), Y
The image data may be color image data composed of (yellow) and K (black) data or monochrome image data.

The gradation correction curve setting section 12 stores the gradation image data according to the set gradation correction curve, more specifically, the gradation correction curve set according to the image output condition described later. The gradation image data Gc, which is halftone data obtained by converting the gradation of G, is created and output.

The gradation-converted gradation image data Gc is compared with threshold data constituting a threshold matrix output from a threshold matrix output unit 20 by a well-known binarization processing unit 18, and the binary image data ( (Halftone image data) Ha. That is, when the threshold value data is TD, the binarization processing unit 18 performs a magnitude comparison operation of G> TD (ON, 1, blackening) and G ≦ TD (OFF, 0, non-blackening),
It outputs binary image data Ha that takes the value 1 or the value 0 of the comparison operation result.

In this case, the threshold value matrix corresponds to a halftone condition set by the halftone condition setting unit 22 via the operator, for example, a condition comprising a set of screen ruling, halftone angle, halftone shape. The data is output from the threshold value matrix output unit 20 to the binarization processing unit 18.

Either the binary image data Ha output from the binarization processing unit 18 or the binary image data (hereinafter, also referred to as test pattern data) Ht of the test pattern output from the test pattern generation unit 24. The data is selected by the multiplexer 26 and is input to a laser scanning exposure unit 32 which is a light beam scanning exposure unit included in the output unit 30. The laser scanning exposure unit 32 scans and exposes the film original Fo coated with a predetermined photosensitive material having a certain γ characteristic with a laser beam, which is a light beam, according to the input binary image data Ha and Ht. The image as a latent image is recorded on a film original plate Fo. Normally, the laser scanning exposure section 32 forms a two-dimensional image on the film original Fo by scanning the film original Fo conveyed in the sub-scanning direction with a laser beam in the main scanning direction.

The film original Fo on which the latent image is recorded is supplied to the developing unit 34 and is developed with a predetermined developing solution at a predetermined temperature for a predetermined time, so that the latent image on the film original Fo is visualized. A film F on which a halftone image is formed is created.

In this embodiment, a film on which an image corresponding to binary image data Ha is formed is denoted by F, and a film on which an image (test pattern) corresponding to test pattern data Ht, which will be described in detail later, is formed. Is denoted by Ft.

The density or halftone area ratio of each pattern constituting the test pattern (test patch) formed on the test pattern film Ft is measured by a measuring device (densitometer or halftone area ratio meter) 36 and measured. The value is supplied to a first input of the tone correction curve generator 14. The second input of the gradation correction curve creating unit 14 is supplied with (the data of) the reference tone curve stored in the reference tone curve storage unit 38.

The tone correction curve creating section 14 has a third input, and measures a reference tone curve from the input terminal 40 in accordance with an image output condition designated by an operator or the like for the test pattern film Ft. Based on the value, the image is converted by a certain algorithm described later, and the image output condition specified by the operator (new image output condition)
A desired tone curve corresponding to is created. The created desired tone curve is inversely transformed to create a new tone correction curve as an inverse function. The newly created gradation correction curve is set in the gradation correction curve setting unit 12.

If the image output condition is a standard image output condition to be described later, or if nothing is set, the gradation correction curve creating unit 14
A tone correction curve (reference tone correction curve) obtained as an inverse function of the reference tone curve read from the reference tone curve storage unit 38 is set in the tone correction curve setting unit 12.

In this case, in this embodiment, the reference tone curve (and the reference gradation correction curve) is
0, the beam diameter of the laser beam in the laser scanning exposure unit 32 is relatively small, the gradient of γ of the photosensitive material applied to the film master Fo is medium, and the degree of deterioration of the developing solution is small. Is moderate and 2
The halftone dot condition (also referred to as halftone pattern condition) of the threshold value matrix set in the value processing unit 18 is standard (for example, 17).
A predetermined angle is given to each plate of CMYK with five lines, and the shape of the halftone dot is square. It is assumed that the image is created in advance under the so-called standard image output conditions at the time of ()). Therefore, as described above, when the image output condition is such a standard, the gradation correction curve setting unit 1
2, the reference gradation correction curve is set.

In this embodiment, the image output condition is hereinafter referred to as a dot condition setting unit 2 for easy understanding.
2 is fixed, the output device 30
It is considered that only the condition changes. However, it is a matter of course that the image output condition may include a change in a threshold matrix condition, that is, a change in a halftone dot condition.

Then, next, when the image output condition is changed from the standard image output condition to a new image output condition, for example, when the beam diameter of the laser beam is made larger, or when the beam diameter becomes smaller, The procedure and operation for creating a new gradation correction curve in the case of using a film original Fo with a large γ of the photosensitive material applied to the film original Fo will be described.

First, FIG. 2 shows an example of a reference tone curve stored in the reference tone curve storage section 38 obtained in advance. 2, the horizontal axis is the input halftone% x _i, the vertical axis represents the output network% y _oi.

Here, the equation of the curve of the reference tone curve is defined as a function represented by the following equations (1) and (2).
(1) from the value of the gradation image data G inputted to the gradation correction curve setting unit 12 G = x _i (i is, for example, 0 to 100%
Is a value of 0 to 255 corresponding to the above, and a value of about 0.4% step) is the value G of the converted gradation image data Gc.
It can be understood that c is obtained as data of _yoi .
From the equation (2), the output value y at the input value x _{i at} an arbitrary point is obtained.
_oi is the output value y _oi-1 point x _i-1 of the previous one, increment [Delta] y _oi at the coordinate point x _i ([Delta] y _oi are usually different value for each coordinate point x _i.) It is understood that this is represented by the value obtained by adding.

[0031] _{y oi = fo (x i)} ... (1) fo (x i) = y oi = y oi-1 + Δy oi ... (2) on the horizontal axis in FIG. 2, x _i = x _Aorg {on the vertical axis Then, y _i = fo
(X _Aorg ) = y _{Aorg し} corresponds to a so-called net attaching portion (also referred to as a net attaching point) on the film F, and x
= X _i = x _{Borg で は On the} vertical axis, y = y _i = fo
(X _Borg ) = y _{Borg す}る corresponds to a so-called net detachment start portion (also referred to as a net detachment start point) on the film F.
Here, the starting point of the netting is a point where the density appears on the film F for the first time when the input halftone% is gradually increased from 0 value. % To value 1
When gradually changing from a value of 100% or less close to 00% to a value of 100%, even if the input dot% value changes, the output dot% value becomes solid or hardly changes, The point at which the density does not change at all or hardly changes at all with respect to the change of the input net%.

The reference tone curve fo (x
_i) during the input network% x _i is x _i = 50% near the point, places the output network% y _i is increased stepwise (step-like), the so-called tone jump (e.g., JP-A-7-336536
It is known that this tone jump is likely to occur at the contact point (contact point) of adjacent halftone dots. For example, when the halftone shape is square, The vertex of the adjacent halftone dot becomes the contact point,
The value occurs near 50%. When the net shape is a round shape, the contact portions of adjacent halftone dots are on the circumference, and tone jump is likely to occur when the halftone percentage is 78.5% (3.14 / 4). .

In the reference tone curve fo of FIG.
Input halftone% x _i is the value x _i = x _c0org (hereinafter, also referred to as a contact portion before point.) At the output network% y _i is the value _{y i} = y c0org next,
For example, 1 input halftone% x _i of the partial apart adjacent its corresponding incremental dot values _{x i} = x c1org (hereinafter, also referred to as a point after contact.) Output dot% in y _i is the value y _i = It changes in a step-like manner with y _c1org .

[0034] Therefore, the equation (2) of the function expression, the value of input halftone% x _i is relatively small variable range (x _Aorg ~x
_C0org) relatively large variable range _(x c1org ~x in _Borg), increment Δy function y for increments [Delta] x _i of the variable x
_oi is assumed to be stored in advance in each input halftone dot% values x _i. Therefore, corresponding to the equation (2), x _i is x _i = x
_i-1 + _{Δx i} and may be considered to be represented.

It should be noted that, as described above, when the function y is a curve, the increment Δy _oi is generally different depending on the value of the constant increment Δx _i of the input network% x _i. It is.

Therefore, when an attempt is made to create a new tone curve (sign is f) when the image output condition is changed to the new image output condition, the image output condition after the change (here described above). As described above, when the beam diameter of the laser beam is larger and the slope of γ of the photosensitive material is steep), the starting point of the halftone dot (x _A , f)
Dot% of (x _A)) (or concentration), the dot% of the contact portion of the halftone
(Or concentration) ｛This is the point before the contact (y _c0 , f
(Y _c0 )) and the dot% of two points of the contact point rear point (y _c1 , f (y _c1 )). In order to obtain｝ and the dot% (or density) of the starting point (x _B , f (x _B )) of the halftone dot, the multiplexer 26 is connected to the test pattern generation unit 24 under the operation of the gradation correction curve creation unit 14. To output predetermined test pattern data Ht.

The contents of the image represented by the test pattern data Ht are shown in the conceptual diagram of the test pattern TP in FIG. As a reminder, what is actually output from the test pattern generation unit 24 is binary image data for a test pattern, that is, test pattern data Ht. However, in FIG. , Conceptually shows an image represented by the test pattern data Ht.

In FIG. 3, in the upper third area E1, the dot%
Are arranged near 0% (the halftone dot percentage gradually increases from 0% from left to right), and in the central region E2, the halftone dot is around 100% (the halftone dot percentage is 100% from right to left). The patch is arranged) and the lower third area E3
In this example, a patch whose half-tone% is close to 50% is arranged. In addition,
In FIG. 3, the patch is depicted as an image in which the dots constituting the halftone dot increase or decrease one by one.

Actually, as shown in FIG. 4, the test pattern TP is, for example, a 1 cm × 1 cm flat net patch 50,
51 and 52 are arranged in each of the regions E1 to E3, respectively, about 10 patches. In this embodiment, the net%
A plurality of patches 50 corresponding to each of 0 to 10%,
A plurality of patches 51 corresponding to 90% to 100% of halftone dots and a patch 52 corresponding to 45% to 55% of halftone dots are generated. In practice, the steps of the mesh% of the patch are about 1%. As shown in FIG. 3, it is preferable that the dots constituting the halftone dot increase or decrease one by one. Note that, as is well known, a flat screen means a uniform density pattern in which a fixed percentage of halftone dots are arranged.
The reason why the size of 52 is set to about 1 cm × 1 cm is to measure the average density using a densitometer having a measuring opening of about φ3 mm as the measuring instrument 36.

In this case, the halftone data A is uniquely obtained from the density (average density Dmean) measured by the measuring device 36 using the equation obtained by solving the following Murray Davis equation (3) with the halftone percentage. In the equation (3), Dmax is a so-called solid density, and usually, Dmax> 4 is used.

A ( ^dot %) = {(1−10 ^−Dmean ) / (1−10 ^−Dmax )} (3) When the measuring device 36 is a halftone dot area meter, the Murray Davis formula {(3 The average density Dme is calculated from the measured dot area ratio A by the equation｝ which is obtained by solving the equation for the average density Dmean.
an can be uniquely calculated.

Based on the test pattern data Ht generated from the test pattern generation section 24, the current output device 3
The laser scanning exposure unit 32 performs laser scanning exposure on the film original Fo under the output condition of 0, in other words, a new image output condition, and develops the exposed film original Fo by the developing unit 34, so that FIGS. A test pattern film Ft in which a test pattern corresponding to the test pattern TP shown in FIG. 4 is formed is created.

The densities of the patches 50, 51, and 52 on the test pattern film Ft are measured by the measuring device 36 in the area E.
1, E2 and E3 are sequentially measured in a scanning manner, so that a halftone dot starting point (x
_A , f (x _A )), which is the halftone dot of the point where the density first appears when the measuring device 36 scans the area E1 (see FIGS. 3 and 4) on the test pattern film Ft. Net% is obtained. Similarly, the dot%
{This is the net% between the contact point front point (x _c0 , f (x _c0 )) and the contact point rear point (x _c1 , f (x _c1 )). In other words, the measuring device 36 is placed on the test pattern film Ft. Region E of
3 When the measured scanned manner halftone% before and after is obtained tone jump (a sudden change in concentration) is generated in the same manner hereinafter, missing start point of the halftone dots (x _B, f (x _B)) of In simple terms, halftone data can be obtained at points where the density deviates from the base density (points at which the density does not change) when the area E3 is scanned and measured by the measuring device 36.

It should be noted that the data obtained by the measuring device 36 is the output net% on the Y axis in FIG. 2, and the values of these output net% are f (x _A ), f (x _c0 ) and f (x _c1 ). ), f (x _B)
The input dot% values corresponding to each value of pre Known values by data output from the test pattern generating section 24, i.e., uniquely to each value of the _{x A, x c0, x c1} , x B Can respond.

Here, the tone curve to be obtained is
The following equation (4) corresponding to the above equations (1) and (2),
(5) It is defined like the function shown by the equation.

[0046] _{y = f (x i) ...} (4) f (x i) = y i = y i-1 + Δy i ... (5) Then, out of the region of the input network% x _i, region x _A ≦ x
_{In the case of i} ≦ x _c0 , as shown in FIG. 5, a function represented by the following equations (6) and (7) may be used.
_{When c1} ≦ x _i ≦ x _B , as shown in FIG.
What is necessary is just to make it the function represented by Formula and Formula (9).

Δy _i = Δy _oi × (f (x _c0 ) −f (x _A )) / (fo (x _c0 ) −f (x _A )) (6) y _xA = f (x _A ) ( 7) Δy _i = Δy _oi × (f (x _B ) −f (x _c1 )) / (fo (x _B ) −fo (x _c1 )) (8) y _xc1 = f (x _c1 ) (9) Therefore, a new tone correction curve obtained by inversely converting a new tone curve based on the equations (6) to (9) is set in the tone correction curve setting unit 12 as a look-up table, and the multiplexer 26 is set to 2 By switching to the value processing section 18 and creating a new film F, even if the image output conditions in the output unit 30 are different, the image output conditions on the image on the film F can be handled. It is possible to obtain a high quality image in which no tone jump occurs.

As described above, according to the above-described embodiment,
Since the new tone curve is obtained by the function approximation formula as shown in the formulas (6) to (9), the time for creating the tone curve and the tone correction curve obtained as the inverse conversion thereof is extremely short. Can be time. Also, when the image output condition changes, the above-described predetermined test pattern data Ht is output, and after being processed by the output device 30,
By outputting the test pattern film Ft and measuring it with the measuring device 36, it is possible to easily obtain the coordinates of the feature points of the function approximation formula. As a result, a new tone curve and gradation correction curve can be easily obtained. Can be created.

In fact, as shown by the solid line characteristics in FIG. 7, a reference tone curve TCr (corresponding to the above-mentioned fo) in the case of using a film master Fo having a small beam diameter and a standard γ of the photosensitive material is γ. ), The tone curve TC1 when the beam diameter is increased (γ of the photosensitive material is the standard γ)
Is shown by the characteristics of the one-dot chain line, and when γ is increased (the beam diameter remains small), the tone curve TC2 is shown by the characteristics of the two-dot chain line. FIG. 8 is an enlarged view of the tone curves TCr, TC1, and TC2 in the vicinity of 50% at which the halftone tone jump has occurred.

Not only does the image output condition of the output device 30 change, but also the halftone dot setting unit 22 changes only the screen ruling without changing the shape of the halftone dot. As a result, the halftone dot condition changes. In such a case, it is not necessary to create a new test pattern for that purpose, and the above-mentioned points (the starting point of the halftone dot, the point before and after the contact point, and the starting point of the halftone dot removal) are calculated by the following conversion formula. Can be calculated.

For example, the starting point (x _A , f (x
_A)), the contact portion before the point of the dot _{(x c0, f (x c0} )) with the contact portion after point _{(x c1, f (x c1} )) and dot the missing starting point (x _B, f (x _B )) are obtained at the same screen-shaped screen ruling Lp, respectively, and the coordinates of each of the obtained points are represented by the screen ruling Lp as a suffix, and the screen dots start to be attached. Point (x
_ALp , f ( _xALp )), the front point of the contact point of the halftone dot ( _xc0Lp , f
_(X c0Lp)) with the contact portion after point _{(x c1Lp, f (x c1Lp} )) and dot the missing start point and _{(x BLp, f (x BLp} )).

At this time, the coordinates of each point in the case where the halftone dot shape is the same and the screen ruling changes from the screen ruling Lp to the screen ruling L are represented by the starting point (x _AL , f
(X _AL )), the contact point before the halftone dot (x _c0L , f
(X _c0L )) and the contact point rear point (x _c1L , f (x _c1L )),
And halftone dot of missing the beginning point when the (x _BL, f (x _BL)), point beginning attached the halftone dots in the screen line number L coordinates (x _AL, f (x _AL)), respectively, (10)
The coordinates of the contact point front point (x _c0L , f (x _c0L )) of the halftone dot having the screen _ruling L can be obtained by the equations (12) and (13). It is possible to ask.

X _AL = x _ALp (L / Lp) ² (10) f (x _AL ) = f (x _ALp ) × (L / Lp) ² (11) x _c0L = x _c1Lp (12) f (X _c0L ) = f (x _cLp ) × α × (Lp / L) (13) α is a constant determined by the output device 30 and the photosensitive material.

The formula is not shown because it is complicated.
Is the starting point (x_BL, F (x _BL))
It is obtained by the same calculation as the equations (10) and (11),
The point after the contact point of the point (x_c1L, F (x_c1L)) Is (1)
It is obtained by the same calculation as the expressions 2) and (13).

[0055] Then, specifically, for example, per start point of known halftone for screen rulings Lp is Lp = 175 lines coordinates _{(x ALp, f (x ALp} )) is (x _ALp, f
If it is known that (x _{AL p} )) = (0.5%, 0.8%), the coordinates when the screen ruling L is L = 350 lines are expressed by equation (10) and (11), respectively. Using the equation, (x _AL , f (x _AL )) = (2%, 3.2%) can be immediately calculated.

Although the present invention has been described with respect to the halftone dot output system as a binary image output device in the above-described embodiment, the present invention is also applied to a multi-value image output device and the same applies. A corrected tone correction curve can be obtained.
In this case, the test pattern may output a highlight-side image, an intermediate image, and a shadow-side image from which the tone reproduction characteristic peculiar to the multi-value image output device can be obtained.

Further, the present invention is not limited to the above-described embodiment, but may adopt various configurations without departing from the gist of the present invention.

[0058]

As described above, according to the present invention, when only a reference tone curve is held and a tone correction curve corresponding to a new image output condition is obtained,
A new image is generated by outputting a test pattern reflected by the output device information and the light-sensitive material information and creating a tone correction curve based on the characteristics of the reference tone curve based on information obtained from the output test pattern. According to the output condition, it is possible to easily create a tone correction curve in which no tone jump occurs in the output image.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an image output system to which a method for creating a gradation correction curve according to an embodiment of the present invention is applied.

FIG. 2 is a diagram illustrating characteristics of a reference tone curve.

FIG. 3 is a conceptual diagram used for describing the configuration of a test pattern.

FIG. 4 is a diagram used for describing an actual configuration of a test pattern.

FIG. 5 is a diagram used to explain when a necessary tone curve is created from a reference tone curve when an image output condition is changed.

FIG. 6 is another diagram used for explaining a case where a necessary tone curve is created from a reference tone curve when an image output condition is changed.

FIG. 7 is a diagram showing an example of a reference tone curve and a new tone curve created from the reference tone curve.

FIG. 8 is an enlarged view of the example shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Image output system 12 ... Tone correction curve setting part 14 ... Tone correction curve creation part 24 ... Test pattern generation part 30 ... Output machine 38 ... Reference tone curve storage part F ... Film Ft ... Test pattern film f ... Tone curve fo: reference tone curve G: gradation image data Ha: binary image data

Claims (6)

[Claims] 1. A method for generating a gradation correction curve for converting gradation of inputted gradation image data into gradation image data corresponding to image output conditions, the method comprising: obtaining a gradation correction curve in advance under a reference image output condition; When a tone curve serving as a reference is prepared, and when the input gradation image data is to be subjected to gradation conversion under a new image output condition, a test pattern is output under the new image output condition, A method of creating a tone correction curve, comprising creating a tone correction curve for a new image output condition based on the reference tone curve based on information obtained from a test pattern. 2. The test pattern according to claim 1, wherein the test pattern includes a halftone dot on the highlight side, a halftone dot contact part, and a halftone dot on the shadow side. Information obtained from the test pattern output under the new image output conditions, the density of the beginning of the dot, the density before and after the contact point of the halftone, and the density of the halftone A method for creating a gradation correction curve, characterized in that the density is the density at the beginning of dropout. 3. The method according to claim 1, wherein the reference image output condition is a condition when the combined performance of the output device and the photosensitive material has a medium level of performance. A method for creating a gradation correction curve characterized by the following. 4. A method according to claim 1, wherein after the input gradation image data is subjected to gradation conversion by a gradation correction curve, a threshold value matrix is operated.
The image output device obtains a film on which a halftone dot image is formed by converting the image data into binary image data, exposing and recording the photosensitive material using the binary image data, and developing the image. The standard obtained under standard output conditions consisting of a material, a standard light beam for exposing and recording a sheet carrying the standard photosensitive material, and a standard developing condition for developing the exposed and recorded sheet is used. A reference tone curve storage unit for storing a tone curve, and when a content of the standard output condition changes, a test pattern is output under the new output condition, and based on information obtained from the test pattern, A tone correction curve creating section for creating a tone correction curve for a new image output condition based on a reference tone curve. 5. The test pattern according to claim 4, wherein the test pattern includes a halftone dot start portion on a highlight side, a halftone dot contact portion, and a halftone dot start start portion on a shadow side. The information obtained from the test pattern output under the new image output condition includes the density at the beginning of the halftone dot, the density before and after the contact point of the halftone dot, and the omission of the halftone dot. An image output apparatus characterized in that the density is at the beginning. 6. The apparatus according to claim 4, wherein the standard output condition is a condition when the combined performance of the output device and the photosensitive material has a substantially medium performance. Image output device.