JP2015051610A - Image forming apparatus and image processing method in image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain readability of output images even when density of the output images is uniformly reduced in order to prevent set-off of a sheet in two-sided printing.SOLUTION: An image forming apparatus 1 comprises image processing means for converting input images into output images, has: sheet determination means 102 for determining presence/absence of set-off of an output sheet in two-sided printing; a color correction part 106 which converts chroma saturation with a predetermined saturation value or less among saturation values of the input images into achroma saturation when the sheet determination means 102 determines that there is the set-off; and an inking processing part 107 (or a γ correction part 108) which uniformly reduces density of the input images converted by the color correction part 106, and prevents the set-off by reducing the density of the input images by the inking processing part 107 (or the γ correction part 108).

Description

  The present invention relates to an image forming apparatus and an image processing method in the image forming apparatus.

  In the image forming apparatus, depending on the thickness of paper to be output, a show-through occurs in which an image formed on the back surface is reflected when double-sided output is performed. Therefore, in order to prevent show-through, the light transmittance of an output medium such as paper (hereinafter simply referred to as paper) is measured to change the surface potential control or writing intensity control of the photosensitive member and set the toner adhesion amount. It is known.

  In this conventional method, in order to reduce the reflection of the back surface, the light transmittance of the paper is measured to set the image forming conditions, and the density of the entire image is uniformly reduced. For this reason, there is a problem that even if a portion having a high density can be output at an optimum density, it is difficult to read the output result from a highlight to a halftone density portion having a middle tone density.

  For example, in Patent Document 1 (Japanese Patent Laid-Open No. 10-161367), the user sets image forming conditions for the purpose of reducing the show-through that the back side image (output content) is transmitted to the front side during double-sided output. In this case, an image density setting method is described in which the light transmittance of a sheet is measured to set the image density in advance.

This image density setting method is similar to the present invention described below in that the image forming conditions are changed based on paper information.
However, in this image density setting method, when the light transmittance of the paper output medium is measured to set the image forming conditions, the density of the entire image is uniformly reduced, so that the output result is difficult to read depending on the information in the document. The problem of becoming is not solved.

  The present invention has been made in view of the above-described conventional problems, and its purpose is to prevent the show-through of the paper, so that when adjusting the image density, even if the density is reduced uniformly, This is to maintain the legibility of the output image.

  The present invention relates to an image forming apparatus including an image processing unit that converts an input image into an output image, and a show-through determination unit that determines the presence or absence of show-through of output paper when duplex printing is performed, and a show-through determination. When the means determines that there is a show-through, the saturation conversion means for converting the saturation below the predetermined saturation value of the saturation value of the input image into achromatic, and the input converted by the saturation conversion means And an image forming apparatus that prevents the show-through by reducing the density of the input image by the density reducing unit.

  According to the present invention, the readability of the output image can be maintained even when the density is uniformly reduced when adjusting the image density in order to prevent the show-through of the paper.

FIG. 1A is a control block diagram of image processing means of the image forming apparatus according to the embodiment of the present invention, and FIG. 1B is a control block diagram of image processing means of the image forming apparatus shown in FIG. 1A. It is a figure which shows an example of the characteristic curve showing the relationship between the input value of saturation, and an output value applied when performing a saturation correction | amendment in a color correction part. It is a figure which shows the characteristic curve which shows the relationship between the input gradation value applied to an inking process part, and an output gradation value in order to perform the conventional general inking process which does not consider show-through. It is a figure which shows the characteristic curve which shows the relationship between the input gradation value applied to the inking process part in order to reduce the gradation value used as the maximum black amount, and an output gradation value. It is a figure which shows the characteristic curve which shows the relationship between the input gradation value applied to the (gamma) correction | amendment part in order to reduce the gradation value used as the maximum black amount, and an output gradation value. FIG. 10 is a flowchart illustrating a processing procedure for preventing show-through performed in an image processing unit of the image forming apparatus. It is another control block diagram of the image processing means of the image forming apparatus. FIG. 6 is a diagram illustrating a scanner γ curve when a paper thickness determination result is used for scanner γ correction. FIG. 10 is a flowchart showing another processing procedure for preventing show-through performed in an image processing unit of the image forming apparatus. FIG. 10 is a flowchart showing still another processing procedure for preventing show-through performed in the image processing means of the image forming apparatus. FIG. 10 is a control block diagram of image processing means in another image forming apparatus. It is a figure which shows roughly the means to measure the transmittance | permeability.

Prior to the description of the embodiments of the present invention, the features of the present invention will be described first.
As already described, if the output sheet is thin, the possibility of show-through increases when duplex printing is performed. In such a case, show-through can be suppressed by lowering the density of the output image as a whole (uniformly).
However, when the density is lowered as a whole, the density of the portion where the density is relatively low from the highlight to the middle density (middle) is also uniformly reduced. For this reason, in the present invention, the saturation of the image is lowered in advance at the time of image input so that the legibility of the image is not lowered even if the density is lowered as a whole. This is because the outline of the image tends to remain by lowering the saturation, and the readability of the image can be maintained even if the density is lowered. Note that it is possible to reduce the density of only the high density portion at the time of output. However, if such a countermeasure is taken, the overall gradation is deteriorated. Therefore, in the present invention, the method of reducing the concentration is uniform.

Next, the features of the present invention described above will be described with reference to the drawings.
1A is a control block diagram of the image processing unit 100 of the image forming apparatus 1 according to the embodiment of the present invention, and FIG. 1B is a control block diagram of the image processing unit 100 of the image forming apparatus 1 shown in FIG. 1A. .
As shown in FIG. 1A, the control block of the image processing unit 100 is roughly composed of an input unit 101, a sheet determination unit 102, and an output unit 103, with the image processing unit 100 as the center. Then, a process of converting the RGB color input image of the digital image into a CMYK output image is performed.

  The paper determination unit 102 performs paper determination using data input as device information. That is, normally, when paper is set in the image forming apparatus 1, the size and type of paper are set when setting the tray. At that time, the basis weight of the paper is set as the paper thickness information. Whether or not to output both sides is also determined by the user setting information. This determination result is input to the image processing means 100 for processing.

As shown in FIG. 1B, the image processing means 100 includes a scanner γ correction unit 104, a filter unit 105, a color correction unit 106, an inking process unit 107, a γ correction unit 108, and a gradation processing unit 109.
The image processing unit 100 performs correction processing based on the determination result of the paper determination unit 102. In other words, in this embodiment, the determination result by the paper determination unit 102 is input to the color correction unit 106, the inking unit 107, and the γ correction unit 108 of the image processing unit 100, and processing that reflects the determination result is performed.
In the figure, the determination result by the paper determination unit 102 is drawn so as to be input to the inking processing unit 107 and the γ correction unit 108 at the same time, but is actually input to one of them. There is no simultaneous input.

Here, the sheet determination unit 102 corresponds to the show-through determination unit of the present invention, and determines whether or not show-through is performed when double-sided printing is performed according to the sheet information, here, the sheet thickness.
The color correction unit 106 corresponds to the saturation conversion unit of the present invention, and changes the saturation value of the input image (input signal) based on the determination of the paper determination unit 102 (determination of whether to show through). I do.
The inking process unit 107 and the γ correction unit 108 correspond to the density reduction unit of the present invention, and are processes for uniformly reducing the density in the input image on which the saturation value changing process has been performed based on the determination of the paper determination unit 102. I do.

Next, the procedure of saturation correction in the color correction unit 106, density reduction processing in the inking processing unit 107, and γ correction unit 108 executed based on the determination result will be described.
FIG. 2 is a diagram illustrating an example of a characteristic curve representing the relationship between the saturation input value and the output value, which is applied when the color correction unit 106 performs saturation correction.
Here, the saturation value indicates the output value with respect to the input value of the color correction unit 106 as a numerical value (%), assuming that the maximum saturation is 100 (%).
In FIG. 2, a characteristic curve indicated by a broken line indicates an input value correction characteristic at the time of normal operation, and a solid line indicates an example of a low saturation correction characteristic performed at the time of preventing show-through. That is, in the color correction unit 106, for example, the R (red), G (green), and B (blue) values of the input signal are converted into an HLS value (H; Hue (hue) value, L; Lightness (lightness) value, S Saturation (saturation) value), and the saturation of the converted HLS value in the saturation value range (1 to 25% in the illustrated example) is converged to achromaticity (0%). That is, processing for lowering the saturation value is performed. After that, that is, in the range exceeding 25%, the correction characteristics shown in the figure are used so as not to impair the gradation.

Note that the subsequent processing (uniform density reduction processing) is performed by converting the HLS value subjected to the saturation processing into RGB values again. In addition, a commonly used mutual conversion formula of RGB and HLS used in this case can be used. In addition to the above processing, for example, a method of converting RGB values into sRGB (standardRGB) and further converting into L * a * b * can be used.
With this processing, even if the RGB values of the input image read in vary, a certain range (in the example shown, 0 to 25% of the input saturation value) can be treated as an achromatic color, and the next step is inking The amount of inking in the processing unit 107 can be adjusted.

Next, processing for uniformly reducing the density of an image whose saturation has been reduced as described above will be described. Here, prior to this, in order to compare with this, a general inking process known per se (for example, see Japanese Patent Application Laid-Open No. 2007-307885) that does not consider a conventional show-through will be described.
FIG. 3 is a diagram showing a characteristic curve showing the relationship between the input gradation value and the output gradation value applied to the inking process unit 107 in order to perform a conventional general inking process that does not consider show-through. .
By the way, a color area gradation image for printing (cyan (C), magenta (M), yellow (Y), black (K)), which is formed through a RIP (Raster Image Processor), is printed. In the image), the K plate generally has higher visibility per dot than the C, M, and Y plates. For this reason, it is known that in the inking process, when the K plate is used in a low gradation portion where black begins to enter, the graininess increases and the image quality deteriorates.

Therefore, in the normal processing, black is formed with CMY composite black in the low gradation portion where black begins to enter, and processing for inserting the K plate when the density increases is performed. That is, in the general inking process, in order to deal with the problem that the image quality is deteriorated due to the graininess, as shown in FIG. % Or more gradation is set.
Further, the background removal (UCR) processing procedure for the inking process uses a procedure represented by the following expression (1). In the formula (1), p is called a UCR rate and an arbitrary value of 0 <p ≦ 100% is selected.

K = p · min (Y, M, C)
Y '= YK
M ′ = M−K
C ′ = C−K (1)
In other words, equation (1) shows what happens to the value when the data formed in the CMY version is inked. Here, inking is a process of replacing the data amount of C = M = Y with K. Therefore, for example, if the densities are Y = 60, M = 85, C = 90 and p = 100%, the data amount of C = M = Y is 60 in this case, and the equation (1) Thus, after inking, K = 60, Y ′ = 0, M ′ = 25, and C ′ = 30.

In addition, from the relationship between the total amount regulation value and the maximum inking amount, a UCR rate is set so that the total amount regulation processing is not applied even when ink (or toner) is used at the maximum (when forming the maximum black), Reduce ink adhesion. For this reason, the maximum background removal amount (UCR amount) is obtained by the known equation (2), and the UCR amount of each gradation value is obtained by linearizing from the inking start gradation value to the maximum gradation value.
(Total amount regulation value)-(Maximum BG (black generation) amount) = (Amount that the CMY plate can hit)
(Amount that CMY plate can hit) / 3 = (Amount that can be hit per plate)
(Maximum monochrome amount)-(Amount that can be hit per plate) = Maximum UCR amount (2)
In other words, in equation (2), the amount of ink used is calculated. In this equation (2), the UCR rate is calculated and set so as not to be restricted by the total amount of ink (maximum amount of ink placed on paper). That is, when the total amount of ink is restricted, the amount of ink is uniformly cut, so that the desired density is controlled differently. Therefore, it is necessary to prevent this.
In the known general inking process and BG process, as described above (black generation (BG) process) and UCR process (the K image is increased by the BG process, the gradation of each color of CMY is lowered ( To reduce the number of dots) and maintain the overall density and color tone).

FIG. 4 is a diagram showing a characteristic curve showing the relationship between the input tone value and the output tone value applied to the inking processing unit 107 in order to reduce the tone value that is the maximum black amount in this embodiment. .
In the present embodiment, from the result of the show-through determination based on the paper thickness determination, the image forming apparatus 1 employs the inking processing unit 107 as shown in FIG. 4 in order to prevent the show-through without reducing the legibility of the characters. It is set so that the inking amount is maximized at a gradation lower than the maximum gradation to be obtained.
Specifically, the gradation (density) that is the maximum black amount is changed to be 65 to 100%, for example, 70% of the maximum gradation value that the image forming apparatus can take. That is, the density of the input image (input signal) is lowered as a whole.

  As a result, even if the K plate is used in the low gradation portion where black starts to enter, the image quality is prevented from being deteriorated due to the graininess, and the K plate can be actively used at an early gradation. That is, even if the black color of the signal input from the input means (for example, the scanner) 101 is not (R, G, B = 0, 0, 0), the K plate has higher visibility per dot than the CMY plate. Can be used. Therefore, even if the density of the input signal is reduced as a whole, the sharpness of the characters can be maintained.

Next, a process performed by the γ correction unit 108 will be described as another method for reducing the density of the entire input signal.
FIG. 5 is a diagram showing a characteristic curve showing the relationship between the input tone value and the output tone value applied to the γ correction unit 108 in order to reduce the tone value that becomes the maximum black amount.
That is, the process for setting the maximum black amount (K plate amount) to a gradation value lower than the maximum gradation value is not limited to the above-described inking processing unit 107, but instead, the subsequent γ correction unit 108. Can also be implemented.
As shown in FIG. 5, the above-described inking process is performed by adjusting the γ curve for the K plate from a normal γ curve indicated by a broken line to a γ curve indicated by a solid line (that is, lowering the density of the entire image). The same effect can be obtained.
This is realized by γ correction by shifting the γ curve so that the maximum black amount gradation is 65 to 100%, for example, 70% of the maximum gradation value that the image forming apparatus can take. To do.

Next, a processing procedure for show-through reduction performed by the image processing unit 100 using each processing unit (color correction unit, inking unit, and γ correction unit) described above will be described.
FIG. 6 is a flowchart illustrating a processing procedure for preventing show-through performed in the image processing unit 100 of the image forming apparatus 1.
First, when an image output operation is designated for the first time, it is determined whether or not double-sided output is set based on information about the output means (image output means) 103 (S101). When the duplex output is set (S101, setting is present), next, the setting of the change for preventing the show-through from the determination of the sheet determination unit 102 based on the setting of the sheet type (hereinafter simply referred to as the show-through change setting). ) Is determined (S102). Here, when the show-through change setting is made (S102, setting is made), the setting for reducing the show-through is performed (S103). Here, in the show-through reduction setting, the above-described saturation correction and inking process (or γ correction for reducing the density of the entire image) are set. The setting of the inking process (or γ correction) may be set to uniformly reduce the density based on the determination result of the paper determination unit 102.
If there is no setting in each of steps S101 and S102, the normal setting (S104) in which the setting for show-through is not performed.
In this embodiment, processing is performed by switching between normal operation setting and show-through setting according to the processing procedure shown in the flowchart above.

FIG. 7 is another control block diagram of the image processing unit 100 of the image forming apparatus 1.
Compared to that of FIG. 1B, this control block diagram shows that the paper show-through determination result of the paper determination means 102 is also input to the scanner γ correction unit 104 that performs γ correction of the read image read by the scanner. The scanner γ correction unit 104 adds a scanner γ correction, and the other points are the same.
The paper determination unit 102 determines, for example, paper show-through using data input as device information. Normally, when paper is set in the image forming apparatus 1, the size and type of paper are set when setting the tray. At that time, the basis weight of the paper is set as the paper thickness information. Whether or not to output both sides is also determined by the user setting information. The determination result is put into the image processing means 100 and processed.

In FIG. 7, the determination result of the sheet determination unit 102 is input to the scanner γ correction unit 104, the color correction unit 106, and the inking process unit 107 (or γ correction unit 108) of the image forming apparatus 1. Processing that reflects is performed.
Again, the determination result of the sheet determination means 102 is input to the inking process unit 107 (or γ correction unit 108).

FIG. 8 is a diagram illustrating a scanner γ curve when the paper thickness determination result is used for scanner γ correction.
Processing operations up to shading correction (not shown) at the time of image input are the same as those of a normal image forming apparatus. However, in the present embodiment, γ corrected during subsequent scanner γ correction is used.
This is because by adjusting the scanner γ in advance, the predetermined density range of the read image (input image), that is, the output value from highlight to medium density is increased, thereby improving the image density. In other words, when reducing the image density according to the paper thickness information of the output paper, as described above, the overall density is lowered. This is to slightly increase the image density, that is, to increase the image density.
The degree to which the image density is increased may be arbitrarily adjusted based on the test result.

In this embodiment, as shown in FIG. 8, when the paper thickness determination result is single-sided output or the paper thickness is equal to or greater than a predetermined threshold, γ indicated by a broken line is used as a normal operation. Otherwise, γ indicated by a solid line for low saturation is used. In the case of γ correction for low saturation, the output value is increased from medium density to highlight than normal γ.
Therefore, the scanner γ correction unit 104 corresponds to the read image density enhancement unit of the present invention.

FIG. 9 is a flowchart showing a processing procedure in the control block of FIG. 7 for preventing show-through performed in the image processing unit 100 of the image forming apparatus 1.
First, when an image output operation is designated for the first time, it is determined whether double-sided output is set based on information about the output means (image output means) 103 (S201). Here, when the duplex output setting is set (S201, with setting), the sheet determination unit 102 determines whether the show-through change setting is performed based on the sheet type setting (S202). ). When the show-through change setting has been made (S202, with setting), the scanner γ correction unit 104 performs a process of slightly increasing the image density from highlight to medium density in advance, that is, scanner γ correction (S203). Next, processing based on the setting for show-through reduction, that is, processing for increasing the saturation of the image and then decreasing the density uniformly (S204), and outputting.
If there is no setting in steps S201 and S202, normal setting (S205) is made.

FIG. 10 is a flowchart showing still another processing procedure for preventing show-through performed in the image processing unit 100 of the image forming apparatus 1.
When an image output operation is designated for the first time, it is determined from the information of the output means (image output means 103) whether double-side output is set (S301). If the setting has been made (S301, with setting), it is next determined whether or not the show-through change setting has been made based on the paper type setting (S302). When the show-through change setting has been made (S302, with setting), first, the scanner γ correction unit 104 is set to reduce the show-through and γ correction is performed (S303). When there is no setting in steps S301 and S302, normal setting (S307) is performed.

Next, a pattern determination means (not shown) is known per se (see, for example, Japanese Patent Laid-Open No. 2000-125123), and whether or not there is a pattern on each of the front and back of the output based on image area separation information. If there is a design (S304, with design), settings for character / design show-through reduction are performed (S305), and output processing is performed. If there is no symbol (S304, no symbol), setting for character show-through reduction is performed (S306), and output processing is performed.
Here, as the setting for reduction of show-through, the above-mentioned scanner γ correction, saturation correction, and inking process (or γ correction for reducing the density of the entire image) are set. Note that in the case of γ correction, the setting of γ may be set to uniformly reduce the density based on the determination result of the paper determination unit 102, but the density reduction amount is changed depending on the presence or absence of a pattern.

  In other words, when there is a design, the influence on the show-through is large. For example, the density is lowered by 10% and the amount of reduction is increased compared to the case without the design. However, since there is an influence due to the paper thickness, it is not necessary to uniformly set 10%. The numerical value may be appropriately determined in view of the show-through state.

FIG. 11 is a control block diagram of the image processing unit 200 in another image forming apparatus 2.
In the embodiment described above, the device information is used as the paper thickness determination means. However, in this embodiment, the transmittance of the actually output paper is measured and the measurement result is used.
In the present embodiment, the control block includes an input unit 201, a transmittance measuring unit 202, a paper determination unit 203, and an output unit 204 with the image processing unit 200 as the center.
That is, for example, light is transmitted from one side of the paper before conveyance at the time of paper output, and the amount of transmitted light is measured by the transmittance measuring means 202. At this time, a threshold value is provided for the transmitted light amount, and when the transmitted light amount exceeds the threshold value, saturation correction is performed.

FIG. 12 is a diagram schematically showing a means for measuring transmittance.
The transmittance measuring means includes a displacement detection head 212 fixed at the paper transport position. The displacement detection head 212 includes a laser light emitting diode 212a and a phototransistor 212b. The laser light emitting diode 212a and the phototransistor 212b are arranged so that their optical axes are aligned so that the laser emitted from the laser light emitting diode 212a passes through the paper and enters the phototransistor 212b. Accordingly, the amount of light received by the phototransistor 212b is maximized when there is no paper 211 (paper thickness = 0).

When the sheet 211 enters the displacement detection head 212, the amount of light received by the phototransistor 212b decreases accordingly. The greater the paper thickness, the greater the reduction in the amount of light received by the phototransistor 212b. The displacement detection circuit 213 to which the laser light emitting diode 212a and the phototransistor 212b are connected generates a transmittance signal proportional to the amount of light received by the phototransistor 212b (inversely proportional to the paper thickness).
The paper determination unit 203 receives the transmittance signal from the transmittance measurement unit 202 and determines whether the paper is show-through. Subsequent processing is the same as in the embodiment already described.

  As already described, when the density of the paper output medium is set according to the information of the output paper, if it is uniformly reduced, the image density from highlight to halftone is also lowered. On the other hand, in the present embodiment, as described above, the saturation of the entire image can be reduced in advance to deepen the processing from highlight to halftone of the input image. Further, by increasing the black ratio, it is possible to maintain the legibility of the image and reduce the amount of ink (or toner) adhesion. Therefore, when setting the density of the paper output medium using the output paper information, the saturation of the input image is reduced to maintain the visibility of the highlight, and the ink ratio (or toner) is increased by increasing the black ratio. The amount of adhesion can be reduced.

According to this embodiment, the following advantages are further obtained. That is,
(1) As a method of generating black, not only the inking processing unit, but also means for correcting the scanner γ to darken the low density part can maintain the character legibility when the show-through is reduced.
(2) When performing double-sided output, it is possible to determine whether there is a picture that is susceptible to show-through, and to change the output image processing method to reduce show-through.
(3) When determining the transmittance of the output paper, there is an effect of improving the determination accuracy by matching with the actual state of the image forming apparatus.

  DESCRIPTION OF SYMBOLS 1, 2 ... Image forming apparatus, 100, 200 ... Image processing means, 101, 201 ... Input means, 102 ... Paper determination means, 103 ... Output means, 104 ... Scanner γ Correction unit 105 ... Filter unit 106 ... Color correction unit 107 ... Inking processing unit 108 ... γ correction unit 109 ... Tone processing unit 202 ... Transmittance Measurement means 203... Paper determination means 204... Output means 211... Paper, 212.

Japanese Patent Laid-Open No. 10-161367 JP 2006-251047 A

Claims (8)

An image forming apparatus including an image processing unit that converts an input image into an output image,
Show-through judging means for judging whether the output paper is show-through when performing duplex printing;
When the show-through determination means determines that there is show-through, a saturation conversion means for converting the saturation below the predetermined saturation value of the saturation values of the input image to achromatic,
Density reduction means for uniformly reducing the density of the input image converted by the saturation conversion means,
An image forming apparatus that prevents the show-through by reducing the density of the input image by the density reducing unit. The image forming apparatus according to claim 1,
The density reduction means is an inking process means, and the inking process means calculates the gradation value of the input image that is the maximum black amount when inking based on the image converted by the saturation conversion means. An image forming apparatus that performs inking by lowering the maximum gradation value of the image forming apparatus. The image forming apparatus according to claim 1,
The density reduction unit is a γ correction unit, and the γ correction unit sets the gradation value of the input image inked by the inking processing unit based on the input image to be higher than the maximum gradation value of the image forming apparatus. An image forming apparatus that performs γ correction so as to decrease the image. The image forming apparatus according to any one of claims 1 to 3,
Having image reading means,
An image forming apparatus having a density improving means for improving a density up to a predetermined density range of the density of a read image read by an image reading means. The image forming apparatus according to claim 1, wherein:
The image determination means for determining whether or not the input image has a pattern, and when the show-through determination means determines that there is a show-through, the saturation and ink of the image are prevented so as to prevent the show-through based on the determination result. An image forming apparatus that changes the amount. The image forming apparatus according to any one of claims 1 to 5,
An image forming apparatus including a transmittance measuring unit that measures the transmittance of an output sheet. An image processing method in an image forming apparatus provided with an image processing means for converting an input image into an output image,
A show-through determination process for determining the presence or absence of show-through of the output paper when performing duplex printing;
When it is determined that there is a show-through in the show-through determination step, a saturation conversion step of converting saturation below a predetermined saturation value out of the saturation values of the input image to achromatic,
A density reduction step for uniformly reducing the density of the input image converted in the saturation conversion step,
An image processing method for preventing the show-through by reducing the density of the input image in the density reduction step. The image processing method according to claim 7,
An image processing method including an image reading process and a density improving process for improving a density of a read image read in the image reading process to a predetermined density range.

Images