KR20080048309A - Method for controlling color of print data - Google Patents

Abstract

A method for controlling color of print data is provided to increase satisfaction of color by changing a CLUT(Color Look-Up Table), which changes RGB(Red/Green/Blue) image data into CYMK(Cyan/Yellow/Magenta/Black) image data, through soft-proofing and a gradation chart in a driver according to user preference, and applying the changed CLUT. A reference image loaded in a driver is displayed by soft-proofing with a printer profile(S20), and a gradation chart used for color conversion is displayed by soft-proofing with the printer profile(S30). A part of which color is changed is selected in the reference image(S40). The color selected in the reference image is displayed in the gradation chart(S50). The color displayed in the gradation chart is changed(S60). The changed color is applied to generate a new CLUT(S70). A new ICC profile is generated by using the generated CLUT and is applied to the reference image, and the reference image applying the new ICC(International Color Consortium) file is displayed(S80).

Description

{Method for controlling color of print data}

1 is an exemplary view of a preview screen of general print (print) data.

2 is a configuration diagram for printing general color image data.

3 is a flowchart of a print data color adjustment method according to the present invention;

4 is a conceptual diagram illustrating a color look-up table (CLUT) applied to the present invention.

6 to 8 are diagrams of soft-proofing images respectively appearing at each step of the print data color adjustment method according to the present invention.

9 shows a process for creating a new CLUT in accordance with the present invention.

The present invention relates to a color adjustment method for color matching of RGB image data displayed on a screen and CMYK image data printed by a printer, and more particularly, a color look for converting RGB image data into CMYK image data in a printer driver. The color look-up table (CLUT) can be adapted to the user's preferences using soft-proofing and gradation charts to improve user satisfaction with colors. The present invention relates to a color adjustment method of print data that can be enhanced.

As the use of digital cameras and color printers increases, the user's desire for quality improvement also increases. While applications (applications) provide preview or soft-proofing of image or document data in text editors, image editors, etc. Throughout the image processing process and depending on the characteristics of the printer hardware, the final output data is often different from the image that was 'previewed' or 'soft proofed'. That is, there is a difference between the color (ie, RGB color) seen on the screen of the display device and the color (ie, CMYK color) shown in the printed output. Such soft-proofing generally refers to proofing the appearance of a color image on a display device before outputting the color image to a printer or the like.

Referring to FIG. 1, a method for improving the quality satisfaction of a printed output by adjusting the data on a computer screen before printing the data worked in an application such as a document editing program or an image editing program to a printer is as follows.

As shown in Fig. 1, the driver provided with a preview of the printer can preview the layout of the output object. The layout preview screen of FIG. 1 is a preview screen showing configuration information of a layout, not a print content of an actual printer. In the preview screen shown in FIG. 1, only the screen before the printing data is configured can be viewed, and the preview screen of the actual printed matter cannot be viewed.

If the user checks the Enable preview menu on the screen of FIG. 1 and selects an OK button (clicks), the user can preview the print data as shown before printing. Although FIG. 1 includes a preview screen showing actual print data, detailed print information such as detailed patterns or details of a corresponding data image may be omitted. When the user sees and confirms the preview screen of FIG. 1, that is, when the user clicks the print page button, the printer driver converts the data of the previewed object into data that the printer can recognize and transmits the data to the printer. do.

On the other hand, in an image editing application such as Photoshop, for example, the user may use the soft-proofing function to predict the color at the print output and then drive the printer driver to perform printing. Providing soft-proofing has a problem that it is virtually difficult to make accurate soft-proofing because it cannot predict color change caused by image processing and color matching algorithms performed in the printer driver.

On the other hand, U. S. Patent No. 6,947, 158 stores output data in the form of a file through an image processing / color matching internally in a printer driver; Launch a window for Preview; Blow the stored file in the preview window to be made for image adjustment; Disclosures are made to print after appropriate image adjustment in the preview window. However, US Pat. No. 5,963,216 allows the output data to be properly adjusted in the preview window, but does not apply soft-proofing, so that the adjusted image color in the preview is a characteristic of the printer hardware and color / image processing in the printer. It may vary depending on the process and may differ from the actual printed image color.

Meanwhile, referring to FIG. 2, a data conversion process performed on a driver according to the related art is as follows. That is, when a user outputs an image to the display 10, the RGB image data is transferred to the driver 20. When the RGB image data is transferred to the driver 20, the driver 20 uses the color look-up table (CLUT) 25 stored in one form to convert the RGB image data into CMYK image data to be output from the printer 30. Convert. When the driver 20 converts all of the RGB image data into CMYK image data, the driver 20 transmits the CMYK image data to the printer 30, and the printer 30 prints the transmitted CMYK image data. However, when converting RGB image data into CMYK image data and outputting the same according to the related art, the driver 20 has only one type of CLUT 25 made based on a general color tendency. There was a problem that could be a source of complaint.

Accordingly, a technical problem to be achieved by the present invention is to soft-proof a user's preference for a color look-up table (CLUT) that converts RGB image data into CMYK image data in a driver. The present invention provides a method of adjusting color of print data that can be changed and applied using (soft-proofing) and gradation charts to increase user satisfaction with colors.

According to an aspect of the present invention, there is provided a method of adjusting color of print data, the method comprising: loading a reference image to be used as a reference in a driver; And generating a new color look-up table applied to the ICC profile of the printer by using the reference image so that the user can always express the desired color trend desired by the user. This is provided.

Preferably, soft-proofing and displaying a reference image loaded in the driver into a printer profile; Soft-proofing and displaying a gradation chart to be used for color conversion into a printer profile; Selecting a portion of the reference image to be changed in color; Displaying a color selected from the reference image on the gradation chart; Changing a color displayed on the gradation chart; Applying the changed color to create the new color look-up table.

Advantageously, generating a new ICC profile with the generated color look-up table, and applying and displaying the new ICC profile to the reference image.

Preferably, the gradation chart is a hue gradation chart.

Preferably, selecting a portion of the reference image to be changed in color includes selecting one color or selecting multiple colors within a predetermined area.

EMBODIMENT OF THE INVENTION Hereinafter, the preferred embodiment of the color adjustment method of the print data which concerns on this invention is described in detail, referring an accompanying drawing. In the following description of the present invention, when it is determined that detailed descriptions of related well-known technologies or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. In addition, terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to the intention or custom of a user or an operator. Therefore, the definition should be made based on the contents throughout the specification.

3 is a flowchart of a method of adjusting print data color according to the present invention, FIG. 4 is a conceptual diagram illustrating a color look-up table (CLUT) applied to the present invention, and FIGS. 6 to 8 are prints according to the present invention. A diagram of a soft-proofing image that appears at each step of the data color adjustment method, and FIG. 9 illustrates a process for creating a new CLUT in accordance with the present invention.

First, the print data color adjustment method according to the present invention was invented for the following reason. In other words, if the color of the output image is different from the one intended by the user when conventionally printing the print data in the user's preferred color, the user can take the change of the color of the original image or the color adjustment in the printer driver. There is a way to change to a tab. However, according to the former conventional method, damage to the original occurs, and according to the latter conventional method, the color change that the user wants to change correctly is ambiguous and may cause problems with other colors. There was a problem that needs to be changed. Accordingly, it is an object of the present invention to allow a user to print in a preferred color by easily changing the color look-up table when the printer profile used by the user is in the color look-up table format.

On the other hand, the ICC profile of the printer used in the present invention is in the form of a color look-up table (CLUT). As an example of the CLUT format applied to the present invention, the concept of the CLUT will be described using 17 × 17 × 17 CLUT as an example.

CLUT 17x17x17 is a RGB value divided into 17 levels and matched with CMYK colors to be output to the printer in advance. If the RGB values exactly match the CLUTs, that is, each RGB value is a multiple of 17, the CLUT outputs the CMYK values stored in the location. Each corner point in FIG. 4 is exactly a point 17 times. However, the inner point (CP) is at a point that does not exactly match the multiple of 17. In the case of the inner point CP, a corresponding RGB value is predicted by using a trilinear interpolation method or a tetrahedral interpolation method with reference to the surrounding color. It will be apparent to those skilled in the art that the number of divisions of the CLUT can be varied, such as 9 × 9 × 9 and 33 × 33 × 33.

Hereinafter, the print data color adjusting method according to the present invention will be described in detail with reference to FIGS. 3 to 9.

As shown in FIG. 5, the printer user loads a reference image RI to be used as a reference for color conversion into the printer driver 20 (FIG. 2) (S10). When the reference image RI is loaded in the driver 20, the reference image RI is soft-proofed with the printer profile and displayed on the screen (S20). By soft-proofing the reference image (RI), it is possible to know what color the actual output image can show. Next, a gradation chart (GC) to be used for color selection is soft-proofed with a printer profile and displayed on the screen (S30). Although the color gradation chart is preferably used as the gradation chart GC in the present invention, an XYZ gradation chart, a Lab gradation chart, and the like can also be used.

If step S30 has been performed, the user selects a color to be changed from the reference image RI (S40). The color to be changed can be selected by using a simple mouse click as shown in FIG. 5, or by selecting multiple colors CC_1 and CC_2 as shown in FIG. 7 by dragging the mouse. When the user selects a color to change in the reference image RI, the driver causes the selected color to be displayed as cc, cc_1, and cc_2 on the gray scale chart GC as shown in FIGS. 5 and 7 (S50).

If the user selects a certain area instead of one color in step S40, displaying all the colors in the area on the gradation chart (GC) may cause confusion for the user, so that only the representative color affecting the selected area is expressed. It may be desirable to. Of course, there can be more than one representative color depending on the selection area.

When the user selects a certain area in step S40, the process of finding a representative color is as follows.

It is assumed that the grid of the CLUT of the printer profile is 17x17x17. When the user selects a certain area on the reference image RI by, for example, dragging the mouse, the printer driver performs the following calculation for each color for the colors in the area. For example, if the RGB value is RGB (154, 234, 64), the grid points that can affect this color are each color value divided by 17, the first decimal place, plus 0.5, Remove the bottom seat. In other words, dividing RGB (154, 234, 64) by 17 gives CLUT (9.0, 13.7, 3.7), and adds 0.5 to each and then removes the decimal place, that is, rounds, CLUT (9, 14, 4). )

The values of CLUT (9, 14, 4) are the decisive positions for representing the color selected by the user. To express this again in RGB, multiply each position by 17. Therefore, the CLUTs 9, 14, 4 become RGB (153, 238, 68).

Applying such a processor to all colors in the reference image area, a CLUT set representing a representative color in the area can be obtained.

If the representative color is found as described above, check whether there is an RGB value matching the representative color in the color gamut, and if there is a matching RGB value, display the corresponding RGB value in the user reference image (RI) and the gradation chart (GC). do. However, if there is no RGB value that exactly matches the representative color, the RGB value is located closest to the representative color using the distance formula of two points in space, and the value is converted into the reference image (RI) and the gray scale chart (GC). Mark on.

For reference, the distance formula between two points in space is as follows. When two points are (x1, y1, z1), (x2, y2, z2), the distance between two points in space is given by Equation 1 below.

[Formula 1]

When the step S50 is performed as described above, the user drags the color (cc) (cc_1, cc_2) shown in the gradation chart GC with the mouse, as shown in FIG. , ncc_2) (S60). In FIG. 6 and FIG. 8, the new profile to which the newly changed color is applied in the gray scale chart GC is denoted by the absent symbol NRI.

If the color is changed in the gradation chart (GC) by the step S60, the printer driver calculates a new CLUT using the changed color (ncc) (ncc_1, ncc_2) (S70). Same as

First, when creating a new CLUT, if the changed value of R'G'B 'is larger than the RGB value before the change, side-effects such as tone jump may occur. Therefore, a new CLUT must be manufactured while minimizing side effects. The following methods can be used to minimize side effects.

The RGB value before the change is called BeforeRGB, the R'G'B value after the change is called CenterRGB, and the difference between the two values (CenterRGB-BeforeRGB) is called (ΔR, ΔG, ΔB), respectively. Then, using the Gaussian normal distribution curve with the change by CenterRGB changed to W (weight) for all input RGB, a new CLUT can be obtained with minimal side-effects. The conversion formula related to this is expressed as Equation 2 below.

[Official 2]

In Equation 2, sigma represents a deviation range, and it is preferable to use the verified value by the characteristics of the printer and the color change width.

By using the above formula 2, CMYK conversion of each output RGB value for each input grid of the CLUT using the CLUT of the existing printer profile enables the creation of a new CMYK CLUT for the input RGB.

The printer profile is generated using the new CLUT created in step S80, and the change is displayed on the screen by soft-proofing the reference image input by the user using the printer profile (S80). Thereafter, when the printer profile is finally changed, the color change selected by the user is permanently applied to the print data (S90). Of course, it is desirable to save the previously provided ICC profile so that it can be returned to its original state if necessary.

Accordingly, the present invention can improve the user's satisfaction with the print color by directly adjusting the CLUT to enter the ICC profile so that the user can always express the desired color trend.

As described above, the method for adjusting color of print data according to the present invention includes a user's preference for a color look-up table (CLUT) for converting RGB image data into CMYK image data in a printer driver. In order to meet the requirements of soft-proofing and the gradation chart (Gradation Chart) by applying the change, it provides the user's satisfaction with the color.

Although a preferred embodiment of the present invention has been described in detail above, those skilled in the art to which the present invention pertains may make various changes without departing from the spirit and scope of the invention as defined in the appended claims. It will be appreciated that modifications or variations may be made. Therefore, changes in the future embodiments of the present invention will not be able to escape the technology of the present invention.

Claims (5)

In the color adjustment method of the print (print) data, Loading a reference image to be used as a reference in the driver; And And generating a new color look-up table applied to the ICC profile of the printer using the reference image, so that the user can always express a desired color trend. The method of claim 1, Soft-proofing and displaying a reference image loaded in the driver into a printer profile; Soft-proofing and displaying a gradation chart to be used for color conversion into a printer profile; Selecting a portion of the reference image to be changed in color; Displaying a color selected from the reference image on the gradation chart; Changing a color displayed on the gradation chart; And applying said altered color to create said new color look-up table. The method according to claim 1 or 2, Generating a new ICC profile using the generated color look-up table, and applying the new ICC profile to the reference image to display the new ICC profile. The method of claim 1, And the gradation chart is a hue gradation chart. The method of claim 2, Selecting a portion of the reference image to change the color, Selecting one color or selecting multiple colors within a predetermined area.

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