JPH11261829A - Image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate color noise picture elements without storing pixel data in a memory, to shorten an image processing time and to reduce cost by the reduction of a memory capacity. SOLUTION: This image processor is provided with a monochrome block discrimination circuit 21 for discriminating the presence/absence of a monochrome block from the successive number of monochrome block picture element signals inmb excluding the picture element of a base, a preceding picture element elimination circuit 22 for turning picture element signals for one or two clocks inputted before the monochrome block picture element signals inmb when the monochrome block picture element signal inmb changes from '0' to '1', a preceding picture element addition circuit 24 for turning the picture element signal turned to '0' in the preceding picture element elimination circuit 22 to '1' corresponding to the discriminated result of the monochrome block in the monochrome block discrimination circuit 21 and a succeeding picture element elimination circuit 25 for turning the picture element signals for one or two clocks inputted after the monochrome block to '0' corresponding to the discriminated result of the monochrome block.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mounted on an image forming apparatus such as a digital color copying machine or the like, and determines whether a document image is a color image or a monochrome image.
The present invention relates to an image processing apparatus having a monochrome original discrimination processing function (hereinafter, referred to as an ACS function).

[0002]

2. Description of the Related Art As an image processing apparatus mounted on an image forming apparatus such as a digital color copying machine for copying and outputting a color image read from a document, an image to be processed is a color image or a monochrome image. Some are provided with an ACS function for automatically determining whether or not the data is the same. In a digital color copying machine equipped with an image processing apparatus having an ACS function, if an image read from a document is a color image, a color image forming process is performed based on image data obtained by performing image processing on the color image, If the image read from the document is a monochrome image, a monochrome image forming process is executed based on image data obtained by performing image processing on the monochrome image.

[0003] As a conventional image processing apparatus having an ACS function, Japanese Patent Application Laid-Open No. 9-186852 discloses an image read from a document by a single image reading process divided into a plurality of areas such as pages. A determination is made for each area whether it is a color image area or a monochrome image area, and based on the determination result, whether to output the image data of each area as a color image or a monochrome image is determined. Is disclosed.

Japanese Patent Application Laid-Open No. 9-186852 discloses that
Even when a color image and a monochrome image are mixed in the image read from the original, the image processing and the color image forming process for the color image are not performed on the monochrome image area, thereby saving the developer and developing. It is described that time can be reduced.

However, if there is a monochrome block in which a predetermined number or more of monochrome pixels are continuous in a part of a color document, color blur called color noise may occur at both ends of the monochrome block. In the configuration of Japanese Patent Application Laid-Open No. Hei 9-186852, a color noise pixel generated at an end of a monochrome image area is determined to be a color pixel, and image processing or a color image forming process for a color image is performed on the monochrome image area. Is executed.

Therefore, in a conventional image processing apparatus having an ACS function, it is determined whether each pixel included in an image of one line read from a document is a color pixel or a monochrome pixel. In order to eliminate color noise pixels, pixel data for one line is temporarily stored in a memory, the number of continuous monochrome pixels is counted, and it is determined whether or not a monochrome block exists, and based on the determination result, There is one that removes color noise pixels.

[0007]

However, in a conventional image processing apparatus having a function of removing color noise pixels, pixel data of an image read from a document is temporarily stored in a memory in order to remove color noise pixels. Processing is required, and image processing is prolonged for writing / reading out pixel data, and a memory for storing the pixel data is required, resulting in an increase in cost.

An object of the present invention is to remove color noise pixels without storing pixel data of an image read from a document in a memory, thereby shortening the image processing time and reducing the memory capacity. An object of the present invention is to provide an image processing apparatus capable of realizing cost reduction.

[0009]

According to the first aspect of the present invention, a single or a plurality of pixel signals located in front of a monochrome pixel signal are deleted before determining whether or not a monochrome block exists. It is characterized by the following.

According to the first aspect of the present invention, a single or a plurality of pixel signals located in front of a monochrome pixel signal are determined without determining whether a monochrome block in which a plurality of monochrome pixel signals are continuous exists. Is deleted. Therefore, without discriminating whether a monochrome pixel signal is included in a monochrome block, a pixel signal that may be a color noise pixel is deleted in advance only on the condition that the pixel signal is located in front of the monochrome pixel signal, and the color signal is deleted. There is no need to store a large number of pixel signals to delete pixel signals of noise pixels.

The invention described in claim 2 is characterized in that the pixel signal deleted prior to the determination as to whether or not a monochrome block exists is restored when the monochrome block does not exist.

According to the second aspect of the present invention, the pixel signal deleted on the condition that it is located on the front side of the monochrome pixel signal is restored when the monochrome pixel signal is not included in the monochrome block. Therefore, only the pixel signal of the color noise pixel is reliably deleted, and it is accurately determined whether the image is a color image or a monochrome image.

According to a third aspect of the present invention, a state in which one or a plurality of pixel signals located in front of a monochrome pixel signal are deleted is stored, and the deleted image signal is restored based on the stored content. Features.

According to the third aspect of the present invention, the state where the pixel signal is deleted is stored only on the condition that the pixel signal is located before the monochrome pixel signal, and the pixel signal which is not a color noise pixel is restored based on the stored content. Is done. Therefore, a pixel signal that has not been deleted is not erroneously restored.

According to a fourth aspect of the present invention, one or a plurality of pixel signals located on the rear side of the monochrome block are deleted based on the result of the determination as to whether or not a monochrome block exists. .

In the invention described in claim 4, after determining whether or not a monochrome block is present, one or a plurality of pixel signals located on the rear side of the monochrome block are deleted based on the determination result. You. Therefore, the pixel signal of the color noise pixel located on the rear side of the monochrome block is reliably deleted.

[0017]

FIG. 1 is a block diagram showing a configuration of an image processing apparatus according to an embodiment of the present invention. An image processing apparatus 10 according to an embodiment of the present invention includes a color / monochrome pixel discriminating circuit 1, a color noise removing circuit 2, a pixel counter 3, a color line discriminating circuit 4, and a line counter 5.
And a color original discrimination circuit 6. Image data is input to the image processing apparatus 10 one pixel at a time. The color / monochrome pixel discrimination circuit 1 converts the input image data of each pixel into color pixels, monochrome pixels or gray pixels.
Classified into pixel data of different types. The pixel counter 3 counts the number of input pixel data. The color noise elimination circuit 2 excludes color noise pixels from the counting target of the pixel counter 3. When the input of the pixel data for one line in the main scanning direction is completed, the color line determination circuit 4 determines whether or not the input line is a color line based on the count value of the pixel counter 3. The line counter 5 counts the number of color lines and monochrome lines. The color document discriminating circuit 6 discriminates whether the image of the document is a color document or a monochrome document based on the counting result of the line counter 5.

FIG. 2 is a diagram showing in detail the configuration of a color / monochrome pixel discriminating circuit included in the image processing apparatus. The color / monochrome pixel discrimination circuit 1 includes difference absolute value calculation circuits 11a to 11c, maximum value selection circuits 12a and 12b.
And a pixel comparison circuit 13. The difference absolute value calculation circuits 11a to 11c calculate the difference absolute value of each color component of YMC for each input pixel data. The maximum value selection circuits 12a and 12b include difference absolute value calculation circuits 11a to 11a.
The maximum value of the three difference absolute values calculated in 1c is selected. The pixel comparison circuit 13 includes the maximum value selection circuit 1
The maximum values selected by 2a and 12b are compared with preset threshold values α and β.

In this comparison, the pixel comparison circuit 13
If the maximum value is equal to or larger than the threshold value β, it is determined that the pixel is a monochrome pixel, and the monochrome pixel signal inm is set to “1”. If the maximum value is less than the threshold value α, it is determined that the pixel is a gray pixel. The signal ing is set to “1”, and when the maximum value is equal to or larger than the threshold α and smaller than the threshold β, it is determined that the pixel is a color pixel, and the color pixel signal inc is set to “1” and output to the color noise removal circuit 2.

FIG. 3 is a diagram showing in detail the configurations of the pixel counter 3, the color line discriminating circuit 4, the line counter 5, and the color original discriminating circuit 6 included in the image processing apparatus. In FIG. 3, PCLK is a clock pulse output from a pixel transfer clock that defines the input timing of a pixel signal, and HSYNC is a synchronization signal in the main scanning direction. The same applies to PCLK in FIGS. 5 and 6 described later. The pixel counter 3 includes a monochrome pixel counter 3a, a color pixel counter 3b, and a gray pixel counter 3c. Counters 3a to 3c
Are color noise removal circuits 2 whose details will be described later.
Pixel data CNTEN-MD and color pixel data CNTEN-C after color noise removal output from
The D and gray pixel data CNTEN-GD are counted.

The color line discrimination circuit 4 includes a comparison circuit 4a
To 4c. The comparison circuit 4a outputs 1 in the main scanning direction.
When the input of the pixel data for the line is completed, the count value MDCNT of the monochrome pixel counter 3a is compared with the threshold value A, and when the count value MDCNT is equal to or greater than the threshold value A, the monochrome line signal is set to “1”. When the input of pixel data for one line in the main scanning direction is completed, the comparison circuit 4b
The count value CDCNT of the color pixel counter 3b is compared with a threshold value B, and when the count value CDCNT is equal to or greater than the threshold value B, the color line signal is set to “1”.

Note that the count value CDC is
If NT is less than the threshold value B, the comparison circuit 4 compares the sum of the count value GDCNT of the gray pixel counter 3c and the count value CDCNT weighted by multiplying by a predetermined value ν.
ν · GDCNT + CDCN
If T is greater than or equal to the threshold value C, the color line signal is set to "1".

The line counter 5 comprises a monochrome line counter 5a and a color line counter 5b. The monochrome line counter 5a increments the count value when the monochrome line signal is "1". The color line counter 5b increments the count value when the color line signal is "1".

The color original discrimination circuit 6 includes a comparison circuit 6a. When the input of the pixel data for one sheet is completed, the comparison circuit 6a counts the count value CLC of the color line counter 5b.
NT is compared with a threshold value μ, and when the count value CLCNT is equal to or larger than the threshold value μ, it is determined that the document is a color document and a color document determination signal CI is output.

The color original discrimination circuit 6 may judge whether or not the original is a color original in consideration of the count value of the monochrome line counter 5a.

FIG. 4 is a diagram for explaining in detail the configuration of the color noise elimination circuit included in the image processing apparatus. The color noise elimination circuit 2 includes a monochrome block discrimination circuit 2
1, includes a previous pixel deletion circuit 22, a previous pixel deletion storage circuit 23, a previous pixel addition circuit 24, and a rear pixel deletion circuit 25. The monochrome block determination circuit 21 determines that a monochrome block has been input when a predetermined number of monochrome pixel data inm are continuously input from the color / monochrome pixel determination circuit 1.

Pixels existing before and after the monochrome block are highly likely to contain color noise, and should not be used to determine whether the image is a color image or a monochrome image.
It is necessary to exclude the pixel counter 3 from counting. Therefore, pixels located on the front side of the monochrome block are deleted by the front pixel deletion circuit 22, and pixels located on the rear side of the monochrome block are deleted by the rear pixel deletion circuit 25.

Here, before the monochrome block discriminating circuit 21 performs the monochrome block discriminating process, the color pixel signal inc or the gray pixel signal ing is changed from “1” to “0” by the previous pixel deleting circuit 22 so that the color noise is reduced. The color pixels or gray pixels that are likely to be pixels are deleted in advance, and the fact that the color pixels or gray pixels have been deleted is stored in the previous pixel deletion storage circuit 23, and the monochrome block determination circuit 21 If it is not determined that the color pixel signal is stored in the previous pixel deletion storage circuit 23, the color pixel signal inc or the gray pixel signal ing stored in the previous pixel deletion storage circuit 23 is changed from “0” to “1” in the previous pixel addition circuit 24. .

FIG. 5 is a diagram showing the configuration of the color noise elimination circuit in more detail. Color noise removal circuit 2
In the comparison circuit 20, any one of the YMC color component data constituting the pixel data input to the image processing apparatus 10 is compared with the background threshold value δ. If the color component data is smaller than the background threshold δ, the comparison circuit 20 determines that the image is a background and sets the output signal to “0”. 1 ".

The output signal of the comparison circuit 20 is a color signal
The monochrome pixel signal inm output from the monochrome pixel determination circuit 1 is input to the monochrome block determination circuit 21 together with the monochrome pixel signal inm.
b is input to the monochrome block counter 21a. The monochrome block counter 21a increments the count value when the monochrome block pixel signal inmb is “1”, and the monochrome block pixel signal inmb is “0”.
At the time of reset through the flip-flop. Therefore, the monochrome block counter 21a calculates the color / color
The monochrome pixel discriminating circuit 1 counts the continuous number of only the monochrome block pixels inmb except for the pixels included in the background area of the image among the pixels determined to be monochrome pixels inm.

This monochrome block pixel signal inmb
Is also input to the previous pixel deletion circuit 22. The previous pixel deletion circuit 22 includes the color pixel signal inc and the monochrome pixel signal in output from the color / monochrome pixel discrimination circuit 1.
g is also input. When the monochrome pixel signal inmb changes from “0” to “1”, and the color pixel signal inc changes from “1” to “0”, the previous pixel deletion circuit 22 outputs 1 or 1 according to the REMDTSEL signal. The color pixel signal inc two clocks earlier is changed from “1” to “0”, and when the gray pixel signal ing changes from “1” to “0”, the gray one or two clocks earlier according to the REMDSEL signal. The pixel signal ing is changed from “1” to “0”.

For this reason, the previous pixel deletion circuit 22 is configured, for example, as shown in FIG. In the configuration shown in FIG. 6, consider the case where the monochrome block pixel signal inmb changes from “0” to “1” and the color pixel signal inc changes from “1” to “0”. Monochrome block pixel signal in
mb is output, and the inverter 6
In 2, the “1” state of the current monochrome block pixel signal inmb is inverted to the “0” state, and the output of the OR gate 63 becomes “0”. At this time, the flip-flop 64
The "1" state of the previous color pixel signal inc is inverted to "0" by the inverter 65, and the output signal of the OR gate 63 and the output signal of the inverter 65 both of which are "0" are input to the OR gate 66. , OR gate 66 outputs "0". Therefore, "0" is output from the AND gate 67, and the color pixel signal inc, which was "1" at the previous input, is stored in the flip-flop 68 in a state where it is inverted to "0".

The S terminal of the selector 69 has a REMDTSEL for determining the number of color or gray pixel signals to be deleted before and after the monochrome block.
When the signal is input and the REMDSEL signal is “1”, the state of the monochrome block pixel signal inmb stored two times before in the flip-flop 68 is changed to RMDT.
When the SEL signal is “0”, the power supply voltage
The signal is input to one input terminal of the R gate 70. Also, O
An inverted signal of the current monochrome block pixel signal inmb is input to the other input terminal of the R gate.

Therefore, when REMDTSEL is "1", the output of the OR gate 70 becomes "0", and the monochrome block pixel signal inmb stored two times before in the flip-flop 68 is converted into the inverter 72 and the OR gate 73. And "0" by the AND gate 74. On the other hand, when the REMDTSEL signal is "0", the output of the OR gate 70 becomes "1", and the monochrome block pixel signal inmb stored in the flip-flop 68 two times before is output from the inverter 72 and the OR gate. It is left at "1" by 73 and AND gate 74.

When the count value is less than the predetermined value γ, the monochrome block counter 21a outputs the monochrome block signal mb
Is set to “1”, and when the count value becomes equal to or more than the predetermined value γ, the block is determined to be a monochrome block and the monochrome block signal mb is set to “0”. The monochrome block signal mb output from the monochrome block counter 21a is input to the front pixel addition circuit 24 and the rear pixel deletion circuit 25. The previous pixel addition circuit 24 includes a monochrome block pixel signal inmb and a color pixel signal i that has passed through the previous pixel deletion circuit 22.
nc and the gray pixel signal ing are also input.

If the monochrome block signal mb is "0" when the monochrome block signal mb changes from "1" to "0", the previous pixel addition circuit 24 sets the previous pixel deletion circuit 22 to "0". The color pixel signal inc or the gray pixel signal ing output as it is, and when the monochrome block signal mb is “1”, the previous pixel deletion circuit 22 sets 1 or 2 clocks to “0” according to the REMDTSEL signal. The minute color pixel signal inc or the gray pixel signal ing is set to “1”.

By this processing, the previous pixel adding circuit 24
Based on the monochrome block determination result in the monochrome block determination circuit 21, the color pixel signal or the gray pixel signal previously set to “0” in the previous pixel deletion circuit 22 prior to the determination of the monochrome block remains “0” or “ 1 "and output. That is, the previous pixel adding circuit 24
Is a color pixel signal inc and a gray pixel signal ing that have been set to “0” on the condition that they are located in front of the monochrome block pixel signal inmb by the previous pixel deletion circuit 22.
When the monochrome block pixel signal inmb is included in the monochrome block, the value is kept at "0". When the monochrome block pixel signal inmb is not included in the monochrome block, the value is restored to "1".

The monochrome block pixel signal inmb
In accordance with whether the pixel signal input at the timing before changes from “0” to “1” is the color pixel signal inc or the gray pixel signal ing, the previous pixel deletion circuit 22 causes the color pixel signal inc or Gray pixel signal ing
Is set to "0". Therefore, when the monochrome block pixel signal inmb is not included in the monochrome block, the previous pixel addition circuit 24 outputs only one of the color pixel signal inc and the gray pixel signal ing set to “0” by the previous pixel deletion circuit 22. It must be selected and restored to "1". Therefore, whether the color pixel signal inc or the gray pixel signal ing has been set to “0” in the previous pixel deletion circuit 22 is stored in the previous pixel deletion storage circuit 23, and the previous pixel deletion storage circuit 23 is stored.
The restoration processing of the color pixel signal inc or the gray pixel signal ing in the previous pixel addition circuit 24 is performed with reference to the stored contents of the above.

For this reason, the previous pixel addition circuit 24 and the previous pixel deletion storage circuit 23 are configured as shown in FIG. 6, for example. Now, considering a case where the color pixel signal inc is deleted in spite of the absence of the monochrome block, when the monochrome block does not exist, the monochrome block signal mb is “1”, and both inputs of the AND gate 75 are not performed. Since it becomes "1", the output of the AND gate becomes "1". When the color pixel signal inc is changed from “1” to “0”, the output of the flip-flop 76 configuring the previous pixel deletion storage circuit 23 becomes “1”.
Therefore, the output of the AND gate 77 becomes "1",
In a state where the color pixel signal inc changed from “1” to “0” in the previous pixel deletion circuit 22 is restored to “1”, O
The data is stored in the flip-flop 79 via the R gate 78.

On the other hand, considering the case where the color pixel signal located on the front side of the monochrome block is changed from “1” to “0” by the previous pixel deletion circuit 22, when the monochrome block exists, the monochrome block signal mb is “ 0 ", the outputs of the AND gates 75 and 77 are both" 0 ", and the output state of the OR gate 78 is the flip-flop 80.
It depends only on the state that is remembered. Therefore, when a monochrome block exists, the color pixel signal in
c is stored in the flip-flop 79 as “0”.

The REMDSEL signal is input to the S terminal of the selector 81 in the same manner as the S terminal of the selector 69. The selector 81 sets the REMDTSEL signal to “0”.
Or the output voltage of the AND gate 77 is input to the OR gate 82 depending on whether the signal is “1” or “1”. Therefore, the previous pixel adding circuit 24 restores the color pixel signal of one or two pixels to “1” according to the state of the REMDTSEL signal.

The rear pixel deletion circuit 25 supplies the monochrome pixel signal inmb and the monochrome block signal mb together with the color pixel signal i passed through the previous pixel addition circuit 24.
nc and the monochrome pixel signal ing are input. When the monochrome block pixel signal inmb changes from “1” to “0”, the rear pixel deletion circuit 25 sets the monochrome block signal mb to “0” and changes the color pixel signal inc from “0” to “1”. REMDTSEL if changed to
Color pixel signal in for one or two clocks depending on the signal
If c is changed from “1” to “0” and the gray pixel signal ing changes from “0” to “1”, REMDTSSEL
Gray pixel signal in for one or two clocks depending on the signal
g is changed from “1” to “0”.

For this reason, the rear pixel deletion circuit 25 is configured, for example, as shown in FIG. If a monochrome block exists, the monochrome block signal mb, and
The inverted signals of the monochrome block pixel signal inmb are both "0", and "0" is input from the OR gate 83 to the OR gate 84. On the other hand, the color pixel signal “ing” of “1” stored in the flip-flop 85 is inverted by the inverter 86 and input to the OR gate 84. Therefore, the output signal CNTE of the AND gate 87
N-CD becomes "0".

On the other hand, when there is no monochrome block, since the monochrome block signal mb is "1",
The output signal of the OR gate 83 becomes “1”, and the color pixel signal “inc” is output from the AND gate 87 as CENTEN-CD while being stored in the flip-flop 85.

The SMD terminal of the selector 88 receives the REMDTSEL signal in the same manner as the selectors 69 and 81. The selector 88 sets the REMDTSEL signal to “0”.
Power supply voltage or OR depending on whether
The output signal of the gate 89 is output. Therefore, when the monochrome block signal mb is “0” due to the presence of the monochrome block, both inputs of the OR gate 89 become “0”, and the color pixel signal two clocks behind the monochrome block. Is also changed from "1" to "0" by the AND gate 90.

As shown in FIG. 6, the previous pixel deletion circuit 22, the previous pixel deletion storage circuit 23, the previous pixel addition circuit 24, and the rear pixel deletion circuit 25 are similar to the color pixel signal inc for the gray pixel signal ing. It has a circuit configuration, and performs the same signal processing as that for the above-described color pixel signal inc for the gray pixel signal ing.

[0047]

According to the first aspect of the invention, a single or a plurality of pixel signals located in front of a monochrome pixel signal are deleted without determining whether or not a monochrome block exists. The pixel signal which may be a color noise pixel is deleted in advance only on the condition that the pixel signal is located in front of the monochrome pixel signal without determining whether the monochrome pixel signal is included in the monochrome block. There is no need to store a large number of pixel signals in order to delete the pixel signals of the pixels, and it is not necessary to write / read the pixel signals, thereby shortening the image processing work. The cost can be reduced by eliminating the need for a memory for storage.

According to the second aspect of the present invention, a pixel signal deleted on condition that it is located in front of a monochrome pixel signal is restored when the monochrome pixel signal is not included in a monochrome block. In addition, it is possible to reliably delete only the pixel signal of the color noise pixel and accurately determine whether the image is a color image or a monochrome image.

According to the third aspect of the present invention, the state where the pixel signal is deleted is stored only on condition that the pixel signal is located in front of the monochrome pixel signal, and a pixel which is not a color noise pixel is stored based on the stored content. By restoring the signal, the pixel signal that has not been deleted is not erroneously restored, and it is possible to more accurately determine whether the image is a color image or a monochrome image.

According to the fourth aspect of the present invention, after determining whether or not a monochrome block exists, one or a plurality of pixel signals located on the rear side of the monochrome block are deleted based on the determination result. By doing so, it is possible to reliably delete the pixel signal of the color noise pixel located on the rear side of the monochrome block, and it is possible to more accurately determine whether the image is a color image or a monochrome image.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating in detail a configuration of a color / monochrome pixel discriminating circuit included in the image processing apparatus.

FIG. 3 is a diagram showing in detail the configurations of a pixel counter, a color line discrimination circuit, a line counter, and a color document discrimination circuit included in the image processing apparatus.

FIG. 4 is a diagram illustrating in detail a configuration of a color noise removal circuit included in the image processing apparatus.

FIG. 5 is a diagram showing the configuration of the color noise elimination circuit in more detail.

FIG. 6 is a diagram showing an example of a specific circuit configuration of the color noise elimination circuit.

[Explanation of symbols]

 1-color / monochrome pixel discrimination circuit 2-color noise removal circuit 3-pixel counter 4-color line discrimination circuit 5-line counter 6-color document discrimination circuit 10-image processing device 21-monochrome block discrimination circuit 22-previous pixel deletion Circuit 23-Previous Pixel Deletion Storage Circuit 24-Previous Pixel Addition Circuit 25-Back Pixel Deletion Circuit

Claims (4)

[Claims] 1. An image processing apparatus according to claim 1, wherein a single or a plurality of pixel signals located in front of the monochrome pixel signal are deleted before determining whether or not a monochrome block exists. 2. The image processing apparatus according to claim 1, wherein the pixel signal deleted before determining whether or not a monochrome block exists is restored when the monochrome block does not exist. 3. A storage means for storing a state in which a single or a plurality of pixel signals located in front of a monochrome pixel signal are deleted, and the deleted image signal is restored based on the storage contents of the storage means. An image processing apparatus according to claim 1. 4. The image processing apparatus according to claim 3, wherein one or a plurality of pixel signals located on the rear side of the monochrome block are deleted based on a result of the determination as to whether a monochrome block exists.