JP2023069216A - Image processing device, printer, image processing method, and program - Google Patents

Abstract

To properly decide a correction amount for correcting a thin line of a color expressed without application of a color material.SOLUTION: An image processing device for correcting a thin line included in an image of a printing object comprises: acquisition means which acquires a read image of a printed matter of a chart image obtained by a printer; measurement means which measures the width of a blur generated in a boundary between a margin part to which a color material is not applied by the printer and a portion other than the margin part in the read image; and decision means which decides a correction amount for correcting a thin line of a color expressed without application of the color material in the image of the printing object on the basis of the measured width of the blur.SELECTED DRAWING: Figure 4

Description

The present disclosure relates to technology for correcting image data including fine line portions.

Image data to be printed may include thin line portions such as fine lines and small point characters. There is a technique for correcting image data to be printed so that a printer can print such fine line portions and reproduce them on printed matter.

Japanese Patent Application Laid-Open No. 2004-100001 describes a method for improving the visibility of white fine lines on printed matter by correcting the density values of pixels around the white fine line portion.

JP 2018-133747 A

When correcting the thin white line portion by the method disclosed in Japanese Patent Laid-Open No. 2002-200311, a method of performing correction based on the correction amount determined according to the characteristics of the printer is conceivable. For example, a method of obtaining the characteristics of the printer by printing a thin white line with a specified line width with the printer and measuring the thin white line on the resulting printed matter is conceivable.

However, when the color of the paper is white, by printing multiple objects to which color materials other than white are added, leaving gaps between them, the gaps where no color material is added can be expressed as thin white lines. However, the thin white lines may be crushed by the surrounding coloring materials. For this reason, it may not be possible to detect a thin white line from the printed matter obtained for determining the correction amount. Further, even if a white thin line can be detected from the printed matter, it may not be possible to appropriately acquire the printer characteristics if the thin line is crushed. In this case, there is a possibility that the correction amount cannot be determined appropriately.

An image processing apparatus according to the present disclosure is an image processing apparatus for correcting fine lines included in an image to be printed, and includes acquisition means for acquiring a read image of a printed matter of a chart image obtained by a printing apparatus; measuring means for measuring a width of blur generated at a boundary between a margin portion to which no color material is applied by the printing apparatus and a portion other than the margin portion in the read image; and determining means for determining a correction amount for correcting a fine line of a color expressed by not applying the coloring material in the target image.

According to the technology of the present disclosure, it is possible to appropriately determine a correction amount for correcting a thin line of a color expressed by not applying a coloring material.

1 is a block diagram showing an example of the configuration of an image forming apparatus; FIG. It is a figure which shows an example of a white thin line chart. FIG. 4 is a diagram showing an example of a printed matter obtained by printing a white thin line chart; 1 is a diagram illustrating an example of a functional configuration of an image forming apparatus; FIG. 6 is a flowchart for explaining processing for determining a correction amount used in white thin line correction processing; It is a figure which shows an example of a UI screen. 4 is a flowchart for explaining blur width determination processing; It is a figure which shows an example of an edge part image. FIG. 4 is a diagram showing an example of a profile of reflectance in an image; 4 is a flow chart for explaining a line width determination process for a white thin line; FIG. 4 is a diagram showing an example of a partial image including a region printed with white thin lines; FIG. 4 is a diagram showing an example of a profile of reflectance in an image; FIG. 4 is a diagram showing an example of a profile of reflectance in an image; It is a block diagram which shows an example of the functional structure of a correction|amendment part. It is a figure for demonstrating correction|amendment of the white thin line based on correction amount. FIG. 10 is a diagram showing an example of a UI screen showing correction results of white fine lines; It is a figure for demonstrating correction|amendment of the white thin line based on correction amount. FIG. 4 is a diagram showing an example of a table for determining a corrected pixel value from a white thin line correction amount; It is a figure for demonstrating correction|amendment of the white thin line based on correction amount.

Hereinafter, the technology of the present disclosure will be described in detail according to embodiments with reference to the accompanying drawings. Note that the configurations shown in the following embodiments are merely examples, and the technology of the present disclosure is not limited to the illustrated configurations.

<Embodiment 1>
[About system configuration]
FIG. 1 is a diagram showing an example of the configuration of an image forming system according to this embodiment. The image forming system 100 includes a PC 101 and a printer 104 which is an image forming apparatus. A printer 104 is connected to a PC (personal computer) 101 via a network 103 . The network 103 is, for example, LAN or WAN.

The PC 101 uses a printer driver to generate PDL (Page Description Language) data based on digital data generated by an application. The PC 101 transmits the generated PDL data to the printer 104 via the network 103 to cause the printer 104 to print an image indicated by the generated data. A monitor 114 is connected to the PC 101 . By displaying an image based on digital data generated by the application on the monitor 114, the user can confirm the color and shape represented by the generated data.

The printer 104 is a printing device that includes the function of an image processing device that corrects white thin lines in an image, which will be described later. Printer 104 has CPU 105 , memory 106 , HDD section 107 , UI display section 108 , image processing section 109 , print section 110 , scanner section 111 , network I/F 112 and bus 113 .

A CPU 105 controls the entire printer 104 . For example, by executing a predetermined program, the CPU 105 interprets the PDL data received by the printer 104 with a PDL interpreter and converts it into bitmap data for printing by rendering. Rendering may be done in hardware rather than in software.

A network I/F 112 is an interface for connecting the printer 104 to the PC 101 or another device (not shown) via the network 103 . The printer 104 can exchange various data with the PC 101 or other devices via the network I/F 112 .

A memory 106 is composed of a RAM as a work area for the CPU 105 and a ROM for storing various programs. The HDD unit 107 is composed of, for example, a hard disk drive or flash memory, and is used to store an OS, programs, PDL data received from the PC 101, image data of a read image obtained by scanning, and the like.

The UI display unit 108 has a display (display unit) for performing various displays. The UI display unit 108 also has a function of an operation unit, and may be composed of a touch panel, or may have buttons as an operation unit. For example, the UI display unit 108 displays a series of operation screens (see FIG. 6) for executing automatic white fine line correction and automatic white fine line correction results (see FIG. 16). The CPU 105 also functions as a display control unit that displays those screens.

An image processing unit 109 performs image processing such as processing for converting bitmap data obtained by interpreting PDL data into print data for printing.

The print unit 110 performs print output (printing) on a recording medium such as paper based on the print data image-processed by the image processing unit 109 . The scanner unit 111 is a reading device for reading a document and generating data of a read image of the document.

Each unit in printer 104 is interconnected via bus 113 . A program that implements various operations or processes in the printer 104 is stored in a computer-readable medium including the HDD unit 107, for example. A program is loaded from a computer-readable medium into the RAM, and the CPU 105 executes the program to implement various operations or processes in the printer 104 .

[Outline of line width correction for thin white lines]
FIG. 2 is a diagram showing an example of image data of the white thin line chart 201. As shown in FIG. The image data of the white thin line chart is image data in which a white thin line (white thin line) with a predetermined line width is designated. A fine line refers to a line of a given width, such as 0.12pt, or 600 dpi 1 dot width, as shown in FIG. A white thin line chart 201 is image data designated to print a plurality of white thin lines. When the paper is white, the white thin line chart 201 is printed so that two black rectangles 205 and 206 are arranged with a gap of 600 dpi 1 dot, and a gap is provided to which coloring materials such as toner and ink are not applied. The image data expresses a thin white line in . The present embodiment will be described on the assumption that the color expressed by providing the regions to which no coloring material is applied is white.

The printer may not be able to reproduce fine lines with the line width specified by the image data. Therefore, there is a method of correcting the image data to be printed so that the printer can reproduce and print the line width specified in the original image data.

For example, the printing unit 110 prints based on the image data of the white thin line chart 201, and the scanner unit 111 reads the resulting printed material as a document to obtain a read image of the printed material. Then, the read image is analyzed to measure the width of the white fine line printed by the printing unit 110, and the correction amount for correcting the white fine line of the image data to be printed is determined based on the measured width of the white fine line. We can think of a way to do this. However, there are cases where the width of the white thin line printed by the printing unit 110 cannot be measured properly.

FIG. 3 shows an example of printed matter 300 obtained as a result of printing based on the image data of the white thin line chart 201 of FIG. As described above, the printing unit 110 prints the areas other than the white thin lines in black or the like, and reproduces the areas to which no color material is applied as white thin lines. However, blurring may occur at the boundary between the blank area, which is an area to which the coloring material is not originally applied, and the area other than the blank area, which is an area to which the coloring material is applied. If the width of the blur is wide, it may not be possible to reproduce the thin white lines on the printed matter according to the image data.

Areas 305 and 306 of the printed matter 300 in FIG. A white thin line cannot be formed. The width of the thin line printed by the printer cannot be properly measured from the read image obtained by reading the printed matter 300 of FIG. 3 with the scanner unit 111 . For this reason, in this embodiment, a method of determining a correction amount for correcting a thin line even when the white thin line cannot be detected from the read image as shown in FIG. 3 will be described.

[Function configuration]
FIG. 4 is a block diagram showing the configuration of the functions of the printer 104 related to white fine line correction according to this embodiment. The printer 104 has an image output control unit 401 , an image reading control unit 402 , a blur width measurement unit 403 , a white thin line width measurement unit 404 , a correction amount determination unit 405 , a correction amount setting unit 406 and a correction unit 407 .

The image output control unit 401 controls the print unit 110 to print an image based on image data to be printed. The image output control unit 401 performs control for printing white thin lines for determining the correction amount based on the image data of the white thin line chart 201 in FIG. 2, for example.

The image reading control unit 402 performs control for reading a document by the scanner unit 111 and obtaining a read image of the document. For example, the image reading control unit 402 causes the scanner unit 111 to read the printed material of the white thin line chart 201 obtained by the control performed by the image output control unit 401, and generates a read image including the printed white thin lines. do.

A blur width measurement unit 403 measures the width of blur (bokeh width) generated at the edge margin and the boundary other than the margin from the read image when the white thin line chart 201 is printed. A method of measuring the blur width will be described later.

The white fine line width measuring unit 404 measures the line width of the white fine line printed by the printing unit 110 based on the image data of the white fine line chart 201 from the read image. A method for measuring the line width will be described later.

The correction amount determination unit 405 corrects the thin white lines in the image data to be printed based on either the blur width measured by the blur width measurement unit 403 or the line width of the white thin lines measured by the white thin line width measurement unit 404. Determines the amount of correction for A method of determining the correction amount will be described later.

The correction amount setting unit 406 sets the correction amount determined by the correction amount determination unit 405 to the correction unit 407 .

A correction unit 407 corrects the white thin line using the set correction amount. A correction method will be described later.

The image output control unit 401, the image reading control unit 402, the blur width measurement unit 403, the white thin line width measurement unit 404, the correction amount determination unit 405, and the correction amount setting unit 406 are executed by the CPU 105 using program codes stored in the ROM or the like. It is implemented by developing it in RAM and executing it. Also, the function of the correction unit 407 is included in the function of the image processing unit 109 . 4 may be implemented by an image processing apparatus that is a device different from the printer 104. In FIG.

Alternatively, some or all of the functions of the units in FIG. 4 may be realized by hardware such as an ASIC or an electronic circuit. It may be realized by executing

[Processing for Determining Correction Amount for White Thin Line Correction Processing]
FIG. 5 is a flowchart for explaining a series of processes for determining and setting a correction amount for white thin line correction processing. A series of processes shown in the flowchart of FIG. 5 are performed by the CPU 105 expanding the program code stored in the ROM of the memory 106 or the HDD unit 107 into the RAM and executing the program code. Also, some or all of the functions of the steps in FIG. 5 may be realized by hardware such as an ASIC or an electronic circuit.

In step S<b>501 , the image output control unit 401 causes the print unit 110 to print based on the image data of the white thin line chart 201 in response to the user's instruction to print the white thin line chart 201 .

FIG. 6 is a diagram showing an example of a UI screen for accepting user instructions. The UI screen shown in FIG. 6 is displayed on the UI display unit 108 . The CPU 105 performs display control to display the UI screen shown in FIG. 6A on the UI display unit 108 before starting this flowchart. When the user selects an automatic fine line correction button 601 on the adjustment/maintenance UI screen shown in FIG. 6A, the screen transitions to the automatic fine line correction UI screen shown in FIG. 6B. When the user selects the white line correction button 602 on the UI screen for automatic fine line correction shown in FIG. 6B, the UI screen for automatic white fine line correction shown in FIG. 6C is displayed. When the user selects the white fine line chart print button 603 on the UI screen for automatic white fine line correction in FIG. 6C, the image output control unit 401 executes the process of S501.

In S<b>502 , the image reading control unit 402 causes the scanner unit 111 to read the printed matter obtained by printing by the printing unit 110 as a result of the processing of S<b>501 , and acquires the read image of the printed matter.

After printing the white fine line chart, the CPU 105 changes the screen displayed on the UI display unit 108 from the automatic white fine line correction UI screen shown in FIG. 6C to the automatic white fine line correction UI screen shown in FIG. 6D. transition. In response to the user setting the printed matter obtained as a result of the process of S501 in the scanner unit 111 and selecting the white thin line chart reading button 604 on the UI screen for automatic white thin line correction shown in FIG. , S502 are executed.

By reading a printed matter obtained by printing a white fine line chart 201, which is an image in which predetermined white fine lines are designated, a read image including the white fine lines printed by the printing unit 110 is obtained. By measuring the line width of the white thin line actually printed by the printing unit 110 from this read image, a print showing how much the white thin line printed by the printing unit 110 has changed compared to the white thin line on the image data. The properties of section 110 are obtained.

A white thin line chart 201 in which a white thin line of 600 dpi1dot is specified shown in FIG. 2 is an example of a chart image for measuring the line width of the white thin line, and the line width of the white thin line in the chart image is not limited to 600dpi1dot. When printing a 600 dpi 1 dot line, it tends to be crushed, the thickness tends to change, and there are many cases where correction is necessary. be done.

In addition, the image data to be printed in S501 may be image data including a thin line of the specified line width specified by the user by specifying the thickness of the white thin line (input line width) desired to be corrected. The resolution and line width to be corrected shown in FIG. 6B may be specified by the user through the UI screen. Then, in S501, a chart image having fine lines with the specified resolution and line width may be printed, and in S502, a read image of the printed matter may be obtained. In this case, in this embodiment, a line width of 600 dpi 1 dot is specified.

In S503, the blur width measuring unit 403 measures the width of the blur occurring at one end and the other end of the white thin line chart image printed by the printing unit 110 from the read image obtained as a result of S502. Details of this step will be described later.

In S504, the white thin line width measuring unit 404 measures the line width (output line width) of the white thin line in the chart image printed by the printing unit 110 from the read image obtained as a result of S502. Details of this step will be described later.

In S505, the correction amount determination unit 405 determines whether the line width of the thin white line measured in S504 is smaller than the total blur width of the two ends measured in S503. If the line width of the white thin line is smaller than the total blur width (YES in S505), the process advances to S506, where the correction amount determination unit 405 determines the correction amount from the blur width. The details of determining the correction amount will be described later.

As described above, in this embodiment, when the printer cannot form a white thin line like the printed matter 300, the line width of the white thin line is determined to be smaller than the total blur width, so the correction amount is determined from the blur width. will be

On the other hand, if the line width of the white thin line is equal to or larger than the blurring width of the two ends (NO in S505), the process proceeds to S507. Determine quantity. The details of determining the correction amount will be described later.

In S<b>508 , the correction amount setting unit 406 sets the correction amount determined in S<b>506 or S<b>507 to the correction unit 407 . By setting the correction amount in the correction unit 407, when the print unit 110 prints the image to be printed, the correction unit 407 can automatically correct the image to be printed so that it has appropriate thin white lines. .

[Regarding the measurement process of the edge blur width]
FIG. 7 is a flowchart for explaining blur width measurement processing. Details of the processing of S503 will be described with reference to FIG.

FIG. 8 shows an image clipped from the read image of the printed matter 300, and is an edge image 801 obtained by clipping the area corresponding to the left edge 302. FIG. The white thin line chart 201 is provided with margins to which no color material is applied in addition to the white thin lines, and the end image 801 is an image obtained by cutting out so as to include the adjacent margins. The flowchart in FIG. 7 shows an edge image that is an image of the left edge 302 and an image of the right edge 303 as shown in FIG. is performed for each.

In S701, the blur width measurement unit 403 converts the pixel value of each pixel (x, y) of the read image into a value representing reflectance. For example, when the input image is sRGB, the pixel value of each pixel (x, y) of the read image is converted to the Y component value (CIEY value) of the CIE color space based on Equation (1).
CIEY(x,y)=0,2126R(x,y)+0,7152G(x,y)+0,0722B(x,y) Equation (1)

CIEY (x, y) is a value that indicates brightness in terms of reflectance. That is, the brightest white is obtained with a reflectance of 100% and a brightness of 100. In the present embodiment, it is assumed that pixel values are converted into CIEY values using equation (1). However, the color conversion in this step can be performed by converting pixel values into values representing reflectance into CIEY values. is not limited to the conversion of

In S702, the blur width measuring unit 403 determines the maximum reflectance Rmax, which is the reflectance having the largest value from the reflectances in the read image obtained in S701.

In S703, the blur width measurement unit 403 determines the minimum reflectance Rmin, which is the reflectance with the smallest value from the reflectances in the image obtained in S701.

In S704, the blur width measuring unit 403 calculates Rn, which is the reflectance for n, based on the equation (2) from the maximum reflectance Rmax and the minimum reflectance Rmin.
Rn=Rmin+(n/100)×(Rmax−Rmin) Formula (2)

As a result of visual experiments, the reflectance of the blurred area is a reflectance between the reflectance R10 when n=10 in Equation (2) and the reflectance R40 when n=40 in Equation (2). Suppose it is decided that there is In this case, in this step, reflectance R40 and reflectance R10 are calculated based on equation (2). Then, in a subsequent step, the blur width is measured using the reflectance R40 and the reflectance R10. As described above, in the present embodiment, the blur width is measured using the reflectance R10 and the reflectance R40. The index is not limited to reflectance R40 and reflectance R10.

In S705, the blur width measurement unit 403 initializes the internal counter K with K=1.

Next, S706 to S708 are loop processing, and in S706, the blur width measurement unit 403 measures the blur width of the K-th line (K line) among the horizontal lines in the end image to be processed. This process of measuring the blur width of each line is repeated until all the lines in the end portion image are completed.

For example, when the edge image to be processed is the edge image 801 in FIG. 8 and K=1, the blur width of the first line 802 is measured. The K-line blur width is measured by determining the distance from the position of reflectance R10 to the position of reflectance R40, which is consistent with reflectance subjectivity.

FIG. 9 is a diagram showing the reflectance corresponding to the position on the line of the edge image 801 of FIG. The vertical axis indicates the reflectance, and the horizontal axis indicates the position on the line. The curve is the reflectance profile 901, the dotted line 904 indicates the location of the reflectance R10 values for n=10, and the dotted line 905 indicates the location of the reflectance R40 values for n=40. .

A position indicated by a point 906 that intersects the profile 901 on the dotted line 904 indicating the value of the reflectance R10 is the start position of the blur. A position indicated by a point 907 that intersects the profile 901 on the dotted line 905 indicating the value of the reflectance R40 is the end position of the blur. A width 908 from the position indicated by the point 906 to the position indicated by the point 907 is determined as the blur width of the left edge of the printed matter. For example, in FIG. 9, since the coordinates of the position of the point 906 are 63 and the coordinates of the position of the point 907 are 60, the number of pixels of the width 908 is three. Since one pixel is 10 μm when the resolution of the edge image is 2400 dpi, the width 908 indicating the blur width of three pixels is determined to be 30 μm.

The position where the profile 901 reaches the reflectance R40 is defined as the end position of the blur. This is because As described above, the reflectance R10 and the reflectance R40 for determining the width of the blur are examples, and may be other than these values as long as the width of the blur can be measured.

In S707, the blur width measurement unit 403 determines whether the blur widths of all lines of the edge image have been measured. In the case of the edge image 801 in FIG. 8, it is determined whether or not the measurement of the blur widths of all lines from the first line 802 to the last line 803 has been completed.

If the measurement of the blur widths of all the lines in the edge image has not been completed (NO in S707), the process proceeds to S708. By doing K+1, K is counted up and K is updated. Then, the process returns to S706 to measure the updated K-line blur width.

If the measurement of the blur widths of all lines in the edge image is completed (YES in S707), the process proceeds to S709.

In S709, the blur width measurement unit 403 obtains the average of the measured values of the blur widths of all the lines in the edge image, and determines the resulting value as the blur width of the edge image to be processed.

The blur width measurement unit 403 determines the blur width of the left edge by performing the flowchart of FIG. 7 on the edge image of the left edge 302 cut out from the read image obtained in S502. do. Further, the blur width measurement unit 403 performs the flowchart of FIG. 7 on the edge image of the right edge 303 cut out from the read image obtained in S502, thereby measuring the blur width of the right edge. to decide. Then, the blur width measurement unit 403 adds the left blur width and the right blur width to determine the total blur width.

In this way, since the blurring characteristics of the left edge and the right edge may be different, the blurring width of each of the both edges is determined, and the blurring width of the left edge and the blurring width of the right edge are determined. The blur widths are combined to obtain the final total blur width at the edge. In addition, when the characteristics of the left edge and the right edge are similar, the blur width measurement unit 403 determines only the blur width of one edge and doubles the blur width. may be determined as the total blur width. That is, since the white thin line is sandwiched between the two ends of the area to which the color material is applied, there is no problem if the sum of the blurring widths of the two ends is obtained.

[Description of the detailed flow of the measurement process of the line width of the white thin line]
FIG. 10 is a flowchart for explaining the line width measurement process of the white thin line. Details of the processing of S504 will be described with reference to FIG.

FIG. 11 is a diagram showing a partial image obtained by cutting out a portion of the white fine line chart 201 including the white fine line in the read image of the printed matter of the white fine line chart 201. For example, it corresponds to the area 202 including the white fine line of the white fine line chart 201. It is a partial image obtained by cutting out a part. The processing of the flowchart of FIG. 10 is performed by cutting out a region including a single white thin line as shown in FIG. is performed on a partial image of

FIG. 11A shows a partial image 1101 obtained by cutting out an area 301 corresponding to the area 202 including the white fine lines from the read image of the printed matter 300 in which the white fine lines are crushed as shown in FIG. FIG. 11B shows a partial image 1104 cut out from the read image of the printed matter in which the white fine lines are reproduced.

The processing of the flowchart of FIG. 10 is performed on each partial image obtained by cutting out the region containing each white thin line included in the white thin line chart 201 . Since the white thin line chart 201 in FIG. 2 includes eight white thin lines, the eight partial images corresponding to the eight white thin lines are processed in the flow chart of FIG.

Since the processes of S1001 to S1003 are the same as those of S701 to S703, description thereof is omitted.

In S1004, the white fine line width measuring unit 404 calculates Rn, which is the reflectance for n, based on the above-described formula (2) from the maximum reflectance Rmax and the minimum reflectance Rmin. Assume that the reflectance indicating white is determined as the reflectance R40 when n=40 in Equation (2) as a value consistent with the subjective view of reflectance. In this case, in this step, the reflectance R40 is calculated based on Equation (2). Then, in the subsequent step, the line width is determined by regarding the region with the reflectance R40 or higher as the white thin line region.

In S1005, the white thin line width measurement unit 404 initializes the internal counter K with K=1.

Next, S1006 to S1008 are loop processing, and in S1006, the white thin line width measurement unit 404 measures the width of the white thin line of the K-th horizontal line in the partial image to be processed. The process of measuring the line width of the white thin line for each line is repeated until all lines in the partial image to be processed are completed.

For example, when the partial image to be processed is the partial image 1101 in FIG. 11A and K=1, the line width of the first line 1102 is measured. Alternatively, when the edge image to be processed is the partial image 1104 in FIG. 11B and K=1, the line width of the white thin line in the first line 1105 is measured.

FIG. 12 is a diagram showing reflectance corresponding to positions on lines of a partial image including a white thin line.

FIG. 12(b) is a diagram showing the reflectance corresponding to the position on the line 1105 of the partial image 1104 shown in FIG. 11(b). The curve is the reflectance profile 1205 and shows an example of reflectance when there is a visible thin white line in the partial image. In FIG. 12B, points 1203 and 1204 are points at which the dotted line 1202 indicating the reflectance R40 for determining the line width and the reflectance profile 1205 intersect. The line width of the white thin line is measured based on the width 1206 from the position indicated by point 1203 to the position indicated by point 1204 . For example, when the width 1206 between the coordinates of the position of the point 1203 and the coordinate of the point 1204 is 7 pixels and the resolution of the read image is 2400 dpi, one pixel is 10 μm. is determined as the line width of the white thin line. In this manner, the line width of the white fine line is determined based on the distance between two points at both ends that intersect with the reflectance R40 indicating the line width.

FIG. 12(a) is a diagram showing the reflectance corresponding to the position on the line 1102 of the partial image 1101 shown in FIG. 11(a). A curve is a profile 1201 of reflectance, and shows an example of reflectance when the white thin line in the partial image is crushed and cannot be seen. In FIG. 12A, there is no point where the dotted line 1202 indicating the reflectance R40 for determining the line width and the reflectance profile 1201 intersect. When there is no portion exceeding the reflectance R40, the line width is measured as 0 μm, assuming that there is no white thin line. In the present embodiment, the reflectance R40 is used to measure the line width of the thin line, but the reflectance used for measurement is not limited to R40 as long as the value matches the subjective view of the white thin line.

In S1007, the white fine line width measuring unit 404 determines whether the line width for all lines of the partial image to be processed has been measured. In the case of the partial image 1101 in FIG. 11A, it is determined whether or not line width measurement has been completed for all lines from the first line 1102 to the last line 1103 . In the case of the partial image 1104 in FIG. 11B, it is determined whether or not line width measurement has been completed for all lines from the first line 1105 to the last line 1106 .

If measurement of the line widths of all lines in the partial image to be processed has not been completed (NO in S1007), the process advances to S1008, and the white thin line width measurement unit 404 is operated to set the thin line in the next line as the measurement target. updates K by counting up K by doing K+1. Then, the process returns to S1006 to measure the line width of the fine line in the updated K lines.

If line width measurement for all lines in the partial image to be processed has been completed (YES in S1007), the process proceeds to S1009.

In S1009, the white fine line width measurement unit 404 calculates the average of the line width measurement values obtained from all the lines in the partial image, and applies the result to the line width of the white fine line included in the partial image to be processed. decide.

The white thin line width measurement unit 404 performs the flowchart of FIG. 10 on each of the partial images cut out so as to include each white thin line of the white thin line chart 201, thereby measuring all (8 Determines the line width of the white thin line in the book). Then, the white fine line width measuring unit 404 determines the average of the line width values of all the determined white fine lines as the line width of the white fine line actually printed by the printing unit 110 . Alternatively, the line width of the white fine line printed by the printing unit 110 may be determined by excluding the maximum and minimum determined line widths and calculating the average.

[Processing to determine the correction amount from the line width of the white thin line]
A method of determining the correction amount based on the measurement result of the width of the white thin line obtained as a result of the process of S504 will be described. That is, it is assumed that the line width of the white thin line specified on the data of the white thin line chart 201, which explains the details of the processing of S507 in FIG. 5, is 600 dpi1dot. In this case, if the minimum unit of correction is 1/4 pixel of 600 dpi, the minimum unit of correction is about 10 μm. Also, the blur width or the line width of the white fine line is also measured in units of 10 μm. Therefore, the line width of 600 dpi 1 dot is also set in units of 10 μm. Therefore, the present embodiment will be described assuming that the line width of 600 dpi 1 dot is 40 μm.

Assume that the line width measured from the read image of the white thin line chart 201 printed is 20 μm as a result of the process of S504. in this case,
Data line width 40 μm−Actual line width 20 μm=20 μm
Therefore, since it is necessary to widen the line width of the white thin line on the image data by 20 μm, the line width of the white thin line should be corrected so that both ends are widened by 10 μm. If the correction unit 407 can perform correction control in 1/4 pixel units, white pixels of 0.25 dots (1/4 pixel) at 600 dpi can be added to the left and right of the thin white line, so the amount of correction is 1/4. It is determined as a pixel.

[Method for determining correction amount from blur width]
When the measured value of the line width of the white thin line is not suitable for determining the correction amount, such as when the white thin line printed by the printing unit 110 is crushed, in the present embodiment, correction is performed based on the total blur width obtained as a result of S503. quantity is determined. The details of the process 506 in FIG. 5, which is the process of determining the correction amount from the total blur width in this embodiment, will be described.

FIG. 13 shows the horizontal line reflectance of the area on the print corresponding to area 202 in FIG. An area 202 includes a blur generated when black rectangles 205 and 206 forming white thin lines are printed, and includes a profile indicating the reflectance of the blur.

FIG. 13(a) is a diagram showing a profile of reflectance in the case where white fine lines are crushed and printed. That is, it is a diagram showing the reflectance of horizontal lines in the area 301 in the printed matter 300 of FIG. The reflectance of the blur generated on the right side of the white thin line is represented by profile 901, and width 908 is the width of the blur on the right side. The reflectance of the blur generated on the left side of the white thin line is represented by a profile 1301, and the width 1302 is the width of the blur on the left side. A distance 1303 represents 600 dpi 1 dot (40 μm), which is the line width of the white thin line designated on the white thin line chart 201 .

In this way, when the white fine lines are crushed on the printed matter and the white fine lines are not formed, the blurring occurring on the left and right of the white fine lines overlaps. A dotted curve in FIG. 13A indicates a reflectance profile 1201 of the collapsed white thin line portion, which is similar to the curve indicating the profile 1201 in FIG. 12 .

A method of determining the correction amount from the blur width when the reflectance of the partial image including the white thin line is in the state of FIG. 13A will be described. In S503 of FIG. 5, if the blur width at the left end is determined to be 30 μm and the blur width at the right end is also determined to be 30 μm, the final sum of the blur widths is the right blur width+left blur width. Defocus width=60 μm. Also, from the reflectance profile 1201 of the area where the white thin line is printed, the width of the white thin line is determined to be 0 μm in S504. In this case, since the white fine line width<total blur width, the process proceeds to S506.

In S506, a correction amount for achieving a line width that takes into account the blur width is determined. For example, the line width of the white fine line on the image data may be widened so that the white fine line can be seen, so that blurring occurring on the left and right of the white fine line when the white fine line is printed does not overlap. That is, the image is drawn so that the distance from the left end position of the right blur width 908 to the right end position of the left blur width 1302 is a distance 1303 of 600 dpi 1 dot (40 μm), which is the line width to be reproduced. Correction may be performed so as to widen the line width of the thin white line on the data. In other words, the line width of the thin white line on the image data may be corrected so as to be widened by the blur width of 30 μm in one and the other width directions.

FIG. 13B is a diagram showing the reflectance of white fine lines printed based on the corrected image data after correcting the white fine lines on the image data. As a result of correcting the image data so as to widen the line width of the white thin line, blurring generated from the left and right rectangles forming the white thin line is separated and the white thin line is visible.

As a specific example of determining the correction amount from the blur width, when correcting a white thin line with a line width of 40 μm on the image data, the line width of the white thin line that should be after correction is the desired line width of 40 μm + the total blur width of 60 μm. , 100 μm. When white thin lines are corrected by the method described in Patent Document 1, and when the correction unit 407 can perform correction control in 1/4 pixel units, 30 μm is 0.75 dots (3/4 pixels) at 600 dpi. , this 3/4 pixel is determined as the correction amount.

[Correction Processing of Input Image Using Correction Amount]
FIG. 14 is a block diagram showing an example of functions of the correction unit 407 realized by the image processing unit 109 according to this embodiment. The correction unit 407 has a luminance density conversion unit 1402 , a white thin line thickness determination unit 1403 , a white thin line correction unit 1404 , a white thin line correction amount setting unit 1405 and a halftone processing unit 1406 .

When the bitmap data 1401 is brightness data for normal display, the brightness/density conversion unit 1402 converts it into 8-bit density data for printing.

A thin white line thickness determination unit 1403 determines whether or not the bitmap data 1401 includes a thin line that satisfies a correction condition. The smaller the line width, the more often the thin white lines are crushed during printing. Therefore, the thin white line thickness determination unit 1403 determines whether there is a thin white line with a line width of 600 dpi 1 dot, for example. This correction condition is an example, and the case where the correction condition is a line width of 600 dpi 1 dot is a case where the white thin line is crushed when the printing unit 110 prints a white thin line with a line width of 600 dpi 1 dot.

The white thin line correction amount setting unit 1405 acquires the white thin line correction amount set by the correction amount setting unit 406 and sets the correction amount for white thin line correction.

The fine white line correction unit 1404 uses the correction amount set by the fine white line correction amount setting unit 1405 to adjust the line width of the thin white line in the input image for the fine line determined by the white thin line thickness determination unit 1403 to be corrected. correction.

A halftone processing unit 1406 converts the 8-bit density data into print data 1407 that is data of the number of gradations that the printing unit 110 can handle.

FIG. 15 is a diagram showing an example of processing for correcting the line width of white thin lines included in data of an image to be printed (input image). Each rectangle in FIG. 15 represents a pixel in the image indicated by the density data output by the luminance/density conversion unit 1402 . One rectangle represents one pixel of 600 dpi, and the pixel value of each pixel is specified by multivalued 8-bit data, with a maximum value of 255 (black) and a minimum value of 0 (white). A specific example of correction processing will be described with reference to FIG.

FIG. 15A is a diagram showing part of the image data before correction. The pixel value of pixel 1501 is 255 (black), the pixel value of pixel 1502 is 0 (white), and the pixel value of 1503 is 255 (black). black), and a pixel 1502 indicates part of a white thin line with a line width of 600 dpi and 1 pixel. That is, the left and right direction in FIG. 15 is the width direction of the line (the direction intersecting with the direction in which the thin line extends). Here, for the sake of simplicity, it is assumed that the pixel value of the pixel adjacent to the white thin line is the black value.

A pixel 1502 in FIG. 15A is determined by the thin white line thickness determination unit 1403 to be a thin white line with a line width of 600 dpi 1 dot, which is the correction condition, and is determined to be corrected. Assume that the correction amount is set to 3/4 pixel as described with reference to FIG. 13(b).

When the correction amount is 3/4 pixels, the white thin line correction unit 1404 performs correction by adding 3/4 pixels with a pixel value of white (0) to both sides of the pixel 1502 in the width direction.

FIG. 15B is a diagram showing image data after the image data before correction in FIG. 15A is corrected based on the correction amount of 3/4 pixel. As shown by 3/4 pixels 1504 and 1506 adjacent to both sides of the pixel 1502 representing the white thin line in the width direction, 3/4 pixels with a pixel value of white (0) are added. As a result of this correction, since the white fine line is printed with a line width of 100 μm, the line width of the white fine line reproduced on the printed matter becomes 40 μm, and it is possible to make the white fine line on the printed matter a desired line width. .

In the above description, the correction amount on one side and the correction amount on the other side in the width direction of the white thin line are set as the same correction amount. The correction amount may be set so that the correction amount for . For example, when determining the correction amount from the blur width, if the blur width generated at the left edge and the blur width generated at the right edge are different, one side in the width direction of the white thin line is adjusted accordingly. The correction amount may be set by determining the correction amount for one side and the correction amount for the other side.

FIG. 16 is a diagram showing a display example of the UI screen when notifying the user of the white fine line correction result. By displaying a screen as shown in FIG. 16 on the UI display unit 108, for example, as shown in FIG. Bokeh width, white thin line width, white thin line width after correction, etc. are displayed. By checking the correction result in FIG. 16, the user can grasp the printer characteristics in more detail.

As described above, according to the present embodiment, even if a thin line of a color reproduced by not applying a coloring material is crushed by the coloring material and the thin line of that color cannot be reproduced on a printed matter, the coloring material is applied. It is possible to appropriately determine the amount of correction for correcting the thin line of the color that is reproduced by not applying it. Therefore, it is possible to accurately correct fine lines of a color reproduced by not applying a coloring material.

In this embodiment, the method of determining the correction amount based on either the measured blur width or the line width of the white thin line has been described, but the correction amount may be determined based on the measured blur width. That is, after S504 in the flowchart of FIG. 5, the correction amount may be determined by skipping S505 and proceeding to S506.

<Embodiment 2>
In the first embodiment, as a method of correcting a thin white line on image data, a method of increasing the line width of a thin white line by adding a white pixel of less than one pixel based on a set correction amount will be described. bottom. In this embodiment, as a method of correcting a white thin line, a method of correcting a white thin line by changing a multi-valued pixel value of one pixel adjacent to the white thin line on image data based on a correction amount will be described. This embodiment will be described with a focus on differences from the first embodiment. Parts not specified are the same in configuration and processing as in the first embodiment.

FIG. 17 shows the image data after the correction unit 407 corrects the image data before correction in FIG. FIG. 4 is a diagram showing; Pixels 1701 and 1702 adjacent to both sides in the width direction of the pixel 1502 forming the white thin line in FIG. 17 correspond to the pixels 1501 and 1503 in FIG. 15(a). Pixels 1701 and 1702 indicate that the pixel values have been changed as a result of the correction of this embodiment by the correction unit 407 . The pixel values of pixels 1501 and 1502 on both sides of the white pixel in FIG. The pixel value after this change is called a corrected pixel value. A corrected pixel value is determined based on the correction amount.

FIG. 18 is a diagram showing a table used to determine corrected pixel values from correction amounts. As shown in FIG. 18, when the correction amount is 3/4 pixel, the corrected pixel value is determined to be 64 in 8 bits. Therefore, as shown in FIG. 17, the pixel values of pixels 1701 and 1702 adjacent to the pixel 1502 forming the white thin line are changed from 255 to 64, and the white thin line on the image data is corrected so as to widen the line width. be able to. Therefore, the printing unit 110 can reproduce desired white fine lines so that the white fine lines are not crushed on the printed matter.

As described above, according to the present embodiment, it is possible to correct one pixel of the original resolution such as one pixel of 600 dpi without dividing one pixel.

<Embodiment 3>
In the above-described embodiment, the method of correcting bitmap data by the correction unit 407 implemented by the image processing unit 109 has been described. In this embodiment, an example will be described in which correction is performed when PDL data received by the printer 104 is interpreted by the PDL interpreter. This embodiment will be described with a focus on differences from the first embodiment. Parts not specified are the same in configuration and processing as in the first embodiment. Also, the rendering resolution is assumed to be 1200 dpi or 2400 dpi. Further, since the correction of this embodiment is not a process for bitmap data, the correction unit 407 of this embodiment is implemented by the CPU 105 developing program codes stored in ROM into RAM and executing them. explain.

FIG. 19 is a diagram for explaining an example of processing for correcting the line width of a white thin line according to this embodiment. FIG. 19A is a diagram showing thin lines specified by PDL data before correction. In PDL data, the line width of a line is specified by the number of points.

When the correction condition is a line width of 600 dpi 1 dot, the correction unit 407 determines whether there is a thin white line with a line width of 0.12 pt corresponding to 600 dpi 1 pixel. Then, the correction unit 407 corrects the thin white line having the line width to be corrected by greatly changing the line width based on the correction amount when the PDL data is interpreted by the PDL interpreter. Specifically, correction is performed to widen the line width by adding the number of points based on the correction amount to both sides in the width direction.

FIG. 19B is a diagram showing an image after the PDL data before correction in FIG. 19A is corrected when the correction amount is set to 3/4 pixel. For example, when the correction amount is 3/4 pixel, the correction unit 407 converts the correction amount into a point number of 0.09 pt. Then, as shown in FIG. 19B, the line width of the white thin line after correction is converted to the line width 0.12pt+correction amount 0.09pt+correction amount 0.09pt=0.30pt specified by the PDL data. . Therefore, the line width on the image data is corrected from 40 μm to 100 μm. As a result of the correction of this embodiment, the white fine line is printed with a line width of 100 μm, so the line width of the white fine line on the printed matter is 40 μm, and the white fine line on the printed matter can be made to have a desired line width.

As described above, according to the present embodiment, correction processing can be performed by the CPU 105 executing a program code without using the image processing unit 109 . Therefore, it is possible to add processing more easily than in the case of correction by the image processing unit 109 .

<Other embodiments>
The present disclosure provides a program that implements one or more functions of the above-described embodiments to a system or device via a network or storage medium, and one or more processors in a computer of the system or device reads and executes the program. It can also be realized by processing to It can also be implemented by a circuit (for example, ASIC) that implements one or more functions.

104 printer 402 image reading control unit 403 blur width measurement unit 405 correction amount determination unit

Claims (18)

An image processing device for correcting fine lines included in an image to be printed,
Acquisition means for acquiring a read image of a printed matter of a chart image obtained by a printing device;
measuring means for measuring the width of blur generated at a boundary between a margin portion to which no coloring material is applied by the printing apparatus and a portion other than the margin portion in the read image;
determining means for determining a correction amount for correcting a fine line of a color expressed by not applying the coloring material in the image to be printed, based on the measured width of the blur;
An image processing device comprising: The chart image includes a thin line of color expressed by not applying the coloring material,
further comprising line width measuring means for measuring the line width of a fine line of a color expressed by not applying the coloring material in the read image;
The determining means is
The image processing apparatus according to claim 1, wherein the correction amount is determined based on the measured line width of the thin line or the width of the blur. The determining means is
3. The correction amount is determined based on the measured width of the blur when a thin line of a color expressed by not applying the coloring material is not detected from the read image. image processing device. The determining means is
3. The image processing according to claim 2, wherein when the measured line width of the thin line is smaller than the measured width of the blur, the correction amount is determined based on the measured width of the blur. Device. The determining means is
5. The correction amount is determined based on the measured line width of the fine line when the measured line width of the fine line is greater than or equal to the measured width of the blur. 1. The image processing apparatus according to claim 1. 6. The image processing according to any one of claims 2 to 5, wherein a line width of a thin line of a color expressed by not applying the coloring material in the chart image can be set by a user. Device. The image processing according to any one of claims 1 to 6, wherein the measured width of the blur is a value indicating a sum of widths of the blur generated from the two boundaries in the read image. Device. 8. The apparatus according to any one of claims 1 to 7, further comprising correcting means for correcting, based on the correction amount, fine lines of a color expressed by not applying the coloring material in the image to be printed. The described image processing device. When the determination means determines the correction amount based on the measured width of the blur,
The correction amount is determined so that the width of the fine line of the color expressed by not applying the coloring material in the image to be printed increases as the width of the measured blur increases. 9. The image processing apparatus according to claim 8, characterized by: The correcting means is
Correction is performed by adding pixels of the color expressed by not applying the coloring material to both sides in the width direction of the thin line of the color expressed by not applying the coloring material based on the correction amount. 10. The image processing device according to claim 8 or 9. The correcting means is
10. The method according to claim 8, wherein, based on the correction amount, the correction is performed by changing pixel values of pixels adjacent to both sides in the width direction of the fine line of the color expressed by not applying the coloring material. The described image processing device. The correcting means is
10. The method according to claim 8, wherein the correction is performed by changing a line width of a fine line of a color expressed by not applying the color material specified by PDL data based on the correction amount. Image processing device. The image processing apparatus according to any one of claims 1 to 12, wherein the fine line of the color expressed by not applying the coloring material is a white fine line. The chart image is an image in which a plurality of rectangles of a color representing the colorant are arranged at predetermined intervals, and the printing device prints the rectangles and does not apply the colorant. 14. An image generated such that fine lines of a color to be represented and having a line width corresponding to the predetermined interval are formed on the printed matter. The image processing device according to . The measurement means measures a blur width of the edge of the rectangle in the read image,
15. The image processing apparatus according to claim 14, wherein the determining means determines the correction amount based on the measured widths of the blur at the two ends. 16. A printing device for obtaining the printed matter of the chart image, comprising each means of the image processing device according to any one of claims 1 to 15,
A printing apparatus comprising reading means for reading the printed matter. An image processing method for correcting fine lines included in an image to be printed, comprising:
an acquisition step of acquiring a read image of a printed matter of the chart image obtained by the printing device;
a measuring step of measuring the width of the blur occurring at the boundary between a margin portion to which no coloring material is applied by the printing apparatus and a portion other than the margin portion in the read image;
a determining step of determining a correction amount for correcting a thin line of a color expressed by not applying the coloring material in the image to be printed, based on the measured width of the blur;
An image processing method characterized by comprising: A program for causing a computer to function as each means of the image processing apparatus according to any one of claims 1 to 15.

Images