JPH06113125A - Picture processor - Google Patents

Abstract

PURPOSE:To make the best use of the advantages of two processings and to execute a flexible processing by constituting a gradation processing key means of an organization dither method in a gradation system by means of an error diffusion method where a feedback system is made as a base. CONSTITUTION:A processing indication means 7 gives the selection information. When the selection signals SH0 and SH1 are turned on (on=1 and off=0), a feedback processing is selected. When the selection signal SH0 is '1' and SH1 is '0', organization dither is selected. The state of change-over switches 5 and 14 when the processing is selected is that a switch SS1 is connected to the position of B and a switch SS2 to that of D since there is no feedback in the case of the dither processing. Since threshold information is fetched from a line memory used as an error buffer 10 in the case of the organization dither, a signal DC executes the control. Thus, the size and the form of the dither threshold can freely be set and the flexible processing can be executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus capable of performing error diffusion processing, tissue dither gradation processing, simple gradation processing and the like.

[0002]

2. Description of the Related Art Generally, in a document image processing apparatus capable of handling not only code information but also image information, image information having contrast such as characters and diagrams is fixed to an original read by a reading means such as a scanner. Image information having gradation such as photographs is binarized by a threshold value and is output by a binary printer having a small number of gradations by binarization by a pseudo gradation means such as a tissue dither method. It is like this.

This is because when the read image information is subjected to a simple binarization process with a fixed threshold value, the resolution of the character and line image areas is preserved because the resolution is preserved, but in the area of the photographic image. Since the gradation is not preserved, the image quality deteriorates.

On the other hand, when the read image information is subjected to gradation processing by a systematic dither method or the like, gradation is preserved in the area of the photographic image so that image quality deterioration does not occur, but character and line images Since the resolution is lowered in the area, the image quality deteriorates.

That is, it is impossible for the read image information to satisfy the image quality of each region having different characteristics by a single binarization process.

However, the information based on the binarization error is fed back as a binarization method which satisfies the gradation of the area of the photographic image and has a better resolution than the systematic dither method for the area of the character / line image. By doing so, a method of performing binarization after correcting the subsequent input pixels has been proposed.

[Error diffusion method] (Reference: An Adaptive
Algorithm for Spatial Grayscale, by RW Floyd and
L. Steinberg, Proceeding of the SI, D. Vol. 17-2, p
p.75-77, Second Quarter 1976) is one of the above feedback-type methods, in which the density of the pixel of interest is multiplied by the weighting coefficient in the binarization error of the already binarized peripheral pixels, This is a method of binarizing with a fixed threshold.

FIG. 13 is a block diagram showing the configuration of the binarization process in the "error diffusion method". In FIG. 13, reference numeral 61 is an input image signal, 62 is a correction means for correcting the image information of the target pixel, 63 is a corrected image signal, 64 is a binarizing means for binarizing the corrected image information of the target pixel, and 65. Is a binarized image signal, 66 is a binarization error calculating means for calculating the binarization error of the binarized target pixel, 67 is a binarization error signal, and 68 is an error filter for calculating a weighting error. Weighting coefficient storage means for storing the weighting coefficient, and 69 is a binarization error calculating means 66.
The weighting error calculating means for calculating the weighting error by multiplying the binarization error calculated in step 3 by the error filter weighting coefficient of the weighting coefficient storage means 68, 70 is a weighting error signal, 71 is the weighting error calculated by the weighting error calculating means 69. Error storage means for storing 72
Is an image correction signal.

The binarization process of the "error diffusion method" will be described in detail below.

An input image signal 61 read by an input device such as a scanner is corrected by an image correction signal 7 in a correction means 62.
The correction processing is performed according to 2, and the corrected image signal 63 is output. Binarization means 64 to which the corrected image signal 63 is supplied
Is the corrected image signal 63 and the binarization threshold Th (for example, “80
h ”and attached“ h ”are“ hex ”indicating that they are hexadecimal numbers), and if the corrected image signal 63 is larger than the binarization threshold Th,“ 1 ”is set as the binarized image signal 65. (Black pixel) is output, and if smaller, "0" (white pixel) is output.

Next, in the binarization error calculating means 66, the corrected image signal 63 and the binarized image signal 65 (here, "0h", "1" when the binarized image signal is "0"). In this case, the difference is defined as “ffh”) and the difference is output as a binarization error signal 67.

The error filter shown in the weighting coefficient storage means 68 is a commonly used error filter configuration. Here, “*” in the weighting coefficient storage means 68.
Indicates the position of the pixel of interest. In the weighting error calculating means 69, the weighting coefficients A, B, C and D of the weighting coefficient storing means 68 are added to the binarization error signal 67 (where A = 7/16, B = 1 /).
16, C = 5/16, D = 3/16) to calculate the weighting error 70. That is, the binarization error of the pixel of interest is multiplied by the weighting factors A, B, C, and D to calculate the weighting error of the four pixels around the pixel of interest (pixels corresponding to the positions of the weighting factors A, B, C, and D). calculate.

The error storage means 71 is a weight error calculation means 6
The weight error 70 calculated in 9 is stored, and the weight errors of four pixels calculated by the weight error calculating means 69 are e _A , e _B , and e for the target pixel “*”, respectively.
_C, and stores the sum in the region of the e _D. The image correction signal 72 described above is a signal at the position of “*” and is a signal in which the weighting errors for four pixels calculated by the above procedure are accumulated.

In recent years, also in the gradation processing for a multi-value output device, the above-mentioned binarization means 64 has been used by replacing it with multi-value conversion means that uses thresholds of the number corresponding to the number of multi-valued levels. There is.

On the other hand, the tissue dither method is a method without feedback as shown in FIG.
This is done by adding a periodic dither signal to the threshold value.

For example, as shown in FIG. 14, 81 is an input pixel, 82 is an input pixel 81 and a tissue dither threshold 83.
When the input pixel 81 is larger than the tissue dither threshold value 83, “1” is output, and when it is smaller, “0” is output. The tissue dither threshold 83 is periodic and is shown in FIG.
Shows a 4 × 4 example. The output 84 shows the binarization result. The same method can be extended and used for multi-value dither.

[0017]

As a conventional gradation processing method, either one of an error feedback method such as an error diffusion method and a method that does not use feedback such as a systematic dither method is often used. However, a system using both methods requires a plurality of configurations capable of implementing each method.

The present invention has a gradation processing method by an error diffusion method based on a feedback type method, and is configured so that gradation processing by a systematic dither method is also possible. By switching to the dither method, it is possible to take advantage of both of them, and with this configuration, it is possible to freely set the size, shape, and threshold of the dither threshold, and thus to provide an image processing apparatus that enables flexible processing. With the goal.

[0019]

An image processing apparatus according to the present invention comprises a supply means for supplying image data represented by a plurality of bits in pixel units to a target pixel and peripheral pixels,
Conversion means for converting the image data supplied by the supply means to multivalued data by comparing with a predetermined threshold value; multivalued data from this multivalued means; Calculating means for calculating the error in pixel units based on the image data of 1., first processing means for diffusing the error in pixel units calculated by the calculating means to peripheral pixels of the pixel of interest, and the first processing means. An error buffer for storing a part of the error diffusion amount diffused by the processing means, a part of the error diffusion amount stored in the error buffer and the other part of the error diffusion amount diffused by the processing means are used. In the error diffusion method, the correction amount calculating means for calculating the correction amount by the correction amount calculating means and the correction means for correcting the image data of the pixel of interest from the supplying means by the correction amount calculated by the correction amount calculating means are used. Instructing means for instructing whether to use or tissue dither, setting means for setting the content of the tissue dither in the error buffer when using the tissue dither, when the tissue dither is instructed by the instructing means, from the calculating means A prohibition unit that prohibits the output of the error in pixel units to the first processing unit and prohibits the output of the correction amount from the correction amount calculation unit to the correction unit, and the tissue dither stored in the error buffer. It is composed of output means for sequentially outputting the respective data as the threshold to the conversion means.

[0020]

According to the present invention, in the above-described structure, the gradation processing method by the error diffusion method based on the feedback type method is enabled, and the gradation processing by the tissue dither method is also possible. is there.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of an image processing apparatus of the present invention. This image processing device inputs image information read and input by a reading device such as an image scanner as digital data of, for example, 8 bits per pixel, and performs gradation processing using this device.

The processing method is based on the error feedback type gradation processing method, and enables tissue dithering, simple threshold processing, and the like. The processing instructing means 7 gives the processing method selection signals SH0 and SH1 and other processing information, and both the selection signals SH0 and SH1 are turned on (ON =
1; OFF = 0), feedback processing is selected, selection signal SH0 is 1, tissue dither is selected when selection signal SH0 is 0, and simple threshold processing (simple multi-valued when selection signal SH1 is 1) Processing) is selected. Switching means (switches SS1 and S) when each processing is selected
The states of S2) 5, 14 and the threshold value selection signal DC are described in the table shown in FIG.

In the case of dither processing or simple threshold processing, since there is no feedback, switch SS1 is B, switch SS
2 is connected to the D position. In the case of tissue dither, the threshold information is normally used as an error buffer line memory 1
Since it has to be taken out of 0, the signal DC controls it.

The error correction means 1 in FIG. 1 is means for correcting the input image data by using the feedback correction amount fed back from the switching means 14 to the target image by multi-valued neighboring images. The comparison unit 2 determines whether the image data corrected by the error correction unit 1 is larger or smaller than the threshold value generated by the threshold value generation unit 12,
The result is output.

The output value calculation means 3 determines which of the possible output levels the corrected image data as the comparison result from the comparison means 2 corresponds to, and outputs the output level as a result. Is. The error calculating means 4 is
The difference between the output level from the output value calculation means 3 and the image data corrected by the error correction means 1 is obtained and the error amount due to multi-value quantization is output.

The switching means 5 corresponds to the instructed processing method, that is, by the error feedback control signal S1.
The multi-value quantization error amount (A side) or the zero error (B side) from the error calculating means 4 is selected, and the feedback error amount is obtained.

The means for calculating the error correction amount from the feedback error amount from the switching means 5 is an error filtering means 6 and an error filtering means 6 for calculating the correction amount of the neighboring pixels by an error filter for the feedback error amount. Error buffer 10 for temporarily storing the result (this buffer is shared as a tissue dither threshold buffer as described later) and correction amount calculation for calculating the correction amount for calculating the correction amount corresponding to the pixel of interest It consists of means 13.

The switching means 5 corresponds to the instructed processing method, that is, according to the correction amount control signal S2, the error correction amount (C side) or the zero correction amount (D) from the correction amount calculating means 13.
Side) is selected and the feedback correction amount is obtained.

In the case of the error feedback type processing method or the simple processing method, the threshold value generation means 12 uses the fixed threshold value memory 11.
The content is called from and the threshold value is output. In the case of the tissue dither processing, the dither matrix value stored in advance in the line memory 15 that is also used as the error buffer is called by the control signal DC, the dither threshold value is calculated, and output as the threshold value.

In the case of tissue dither and simple processing, the switch SS1 is connected to the position B by the control signal S1 and the switch SS2 is connected to the position D by the control signal S2, which is a structure without feedback.

An example of the binarization processing based on the above configuration will be described below. This is an example of using the well-known binary error diffusion method as the error feedback method as shown in FIG.

In FIG. 3, the adder 1 adds an input image data (for example, 8-bit digital data read by a scanner) to an error correction amount (for an 8-bit input image signal) from a switching unit 14 which will be described in detail later. Then, the corrected image data is output. When the input image data has 8 bits, the corrected image data has 10 bits and is represented as shown in FIG.

In FIG. 3, a comparison unit 2 as a comparison means.
Compares the corrected image data from the adder 1 with the threshold value Th (1) generated by the selector 12 as a threshold value generation unit, and determines whether the corrected image data is smaller than the threshold value Th (1). , 0 or 1 is output depending on whether it is large.

One example of implementing the above comparison unit 2 is shown in FIGS.
It shows in FIG. In the figure, A0 to A9 represent the bits of the corrected image data shown in FIG. 4, and B0 to B7 represent the threshold values from the threshold value generator 12. As shown in FIG. 5, the comparison unit 2 compares the 10-bit corrected image data with the 8-bit threshold value and outputs a 1-bit comparison result. As shown in FIG. 6, the input side of the comparison unit 2 is composed of an AND circuit 21, inverter circuits 22 and 23, and an exclusive logic loop circuit 24. As shown in FIG. 7, the output side of the comparison unit 2 is composed of AND circuits 25, ..., 27, an OR circuit 26, and an inverter circuit 28.

The comparator 2 outputs 1 when the corrected image data from the adder 1 is larger than the threshold value Th (1), and 0 otherwise. In FIG. 3, input data to the subtracter 4b as an actual value corresponding to the output level (1 bit) of the comparison unit 2 to obtain the binarization error amount (output from the memory 4a as the bit number conversion unit Data) must be retrieved. It can be implemented using an 8 bit × 2 memory 4a. The relationship between the input data and the output data of the memory 4a is shown below as an example of the binarization processing.

That is, when the input data is 0, the output data "00h" is output, and when the input data is 1, the output data "FFh" is output.

The difference between the corrected image data and the output data from the memory 4a is the binarization error amount e (9 bits of e0 to e8, shown in FIG. 8). Whether or not the error is diffused by the process instructed from the binarization error amount e is determined by the switching unit 5 by the control signal S1, and the feedback error amount is output.

The switching section 5 is composed of an AND circuit group, as shown in FIG. The switching unit 5 outputs a binary error as an error amount as it is at the time of error diffusion, and outputs an error amount of zero in the case of tissue dither or simple multi-value quantization processing. FIG. 10 shows an example of how to implement the calculation means for calculating the correction amount from the feedback error amount from the switching unit 5.

In FIG. 10, the error filter 6 as the error diffusion filtering means is provided with multipliers 31, 32, 3
3, 34, adders 35 and 37, and registers 36 and 38. The feedback error amount e and the coefficients A, B, C, and D related to the neighboring positions are multiplied by multipliers 31, 32, and 3, respectively.
The result of multiplication by 3 and 34 is diffused to the corresponding next pixel or the pixel of the next line (see FIG. 13 for an example of setting of A, B, C, and D). Since the error is diffused from the 3 pixels of the previous line to an arbitrary pixel to be processed, the adder 35 and the register 36, in order to store them collectively,
38 are provided.

In order to temporarily store the error amount due to the binarization processing of the previous line, that is, the data from the adder 37 in the line buffer 10. Memory interface 41
It is put into the error information write register 49 inside. The error correction amount corresponding to the pixel of interest is diffused from the adjacent pixel and the error amount supplied from the previous line through the error information read register 48 in the memory interface 41 by using the adder 13. It is obtained by adding the error amount from the multiplier 34 which has been performed.

The error correction amount from the adder 13 is changed by the switching unit 14.
Is output to. The switching unit 14 has the same configuration as the switching unit 5, and outputs the error correction amount from the adder 13 as it is as a feedback correction amount at the time of error diffusion, and outputs zero error correction amount in the case of tissue dither or simple multi-value processing. Output as feedback correction amount.

The threshold value generating unit 12 in FIG. 3 simply functions as a selector in the case of binarization processing, and in the case of error diffusion or simple processing,
The contents from the fixed threshold memory 11 are selected, and in the case of dither processing, the contents called from the line buffer 10 are selected and output as the threshold Th (1). This selection is made by the threshold control signal DC. However, in the case of multi-valued processing, a method for improving the threshold generation unit 12 is required.

For example, in the multi-valued processing, when three-valued processing is performed, two threshold values are required. Therefore, a method of exchanging data with the buffer twice for one threshold value processing or one cycle using multiple data buses is used. There is a method of reading all the threshold values, but when the number of levels is large, such a method is not efficient. As another method, there can be considered a means for generating thresholds for all levels by using the relationship between the thresholds of the number of levels from the threshold value read once. Therefore, in the case of multi-valued processing, it is necessary to improve the threshold generation unit 12 as necessary.

An example of threshold values stored in the fixed threshold memory 11 is shown below.

STEP = (2 ⁿ -1) (m-1) TSTEP = STEP / 2 Th (i) = i * STEP-TSTEP (1) where n: number of bits of input image information, m: output device Number of levels, Th (i); i-th threshold, i = 1,2,3 ..., (m-1) Using the above equation (1), Th (1) for m = 2 and n = 8 = 7Fh (2) Here, h indicates a hexadecimal value. There are several possible methods for creating the dither threshold, and one example of them is described below for the case of (4 × 4) tissue dither.

195 75 150 240 240 165 15 60 120 120 105 45 30 180 225 135 90 210 Next, the memory interface 41 for controlling the data read / write of the line buffer 10 will be described with reference to FIG. The memory interface 41 is provided between the dither threshold address generator 50 in the processing controller 8 and the line memory 10.

As shown in FIG. 11, the memory interface 41 includes an access controller 42, a read address selector 43, an address selector 44, a selector 45, a data selector 46, a dither data register 47, an error information read register 48, and an error information. Write register 4
It is composed of 9.

The access control unit 42 reads / writes data.
In response to the write, the read / write signal is supplied to the line buffer 10, the address selector 44, and the selector 45.

The dither address and the error control read address from the processing controller 8 are supplied to the read address selector 43. The address selector 44 receives the address from the read address selector 43, the error control write address and the select signal (selection signal of dither or error diffusion method) from the processing controller 8, and the read / write signal from the access controller 42. Is being supplied.

The read / write signal from the access control unit 42 is supplied to the selector 45, and at the time of reading, the read data from the line buffer 10 is transferred to the data selector 46.
When writing, the write data from the error information write register 49 is output to the line buffer 10.
The select signal from the processing controller 8 is supplied to the data selector 46, and the data from the selector 45 is selectively supplied to the dither data register 47 or the error information read register 48.

The output (dither information) of the dither data register 47 is supplied to the selector 12. The output (read error information) of the error information read register 48 is supplied to the adder 13. The write error information from the error filter 6 is supplied to the error information write register 49.

That is, when the dither data is read from the line buffer 10, the dither address is supplied to the line buffer 10 via the read address selector 43 and the address selector 44, and the data at that address is selected by the selector 45 and the data selector 46. , To the selector 12 via the dither data register 47.

When the error information is written in the line buffer 10, the error control write address is changed to the address selector 4.
The error information which is supplied to the line buffer 10 via 4 and is written to the line buffer 10 via the error information write register 49 and the selector 45 is stored in the above address.

When the error information is read from the line buffer 10, the error control read address is supplied to the line buffer 10 via the read address selector 43 and the address selector 44, and the data at the address is supplied to the selector 45, the data selector 46, And is output to the adder 13 via the error information read register 48.

Data for dither is set in the line buffer 10 from the outside, for example. For example, in the case of 4 × 4 dither, dither matrix data is set for 16 addresses, and the dither matrix data is repeatedly read and used.

Next, the dither threshold address generator 50 in the processing controller 8 for generating the dither threshold address in the memory interface 41 will be described with reference to FIG.

The dither threshold address generator 50 is shown in FIG.
As shown in FIG.
2, comparator 53, column number setting register 54, adder 55,
Offset row address register 56, comparator 57, row start address register 58, address counter 59
It is composed by.

The dither rows are set in the row number setting register 51. The row counter 52 is a counter that counts each time a line synchronization signal is supplied, and the count value is output to the comparator 53 and cleared by a clear signal from the comparator 53. That is, the row counter 52 is cleared for each dither row set in the row number setting register 51.

The comparator 53 compares the set count number of the row number setting register 51 with the count number of the row counter 52, and when they match, clears the row counter 52 and sends a reset signal to the offset row address register 56. It is what is output.

A dither column is set in the column number setting register 54. The adder 55 adds the set number of columns from the column number setting register 54 and the number of rows of the offset row address register 56, and outputs the addition result to the offset row address register 56.

The offset row address register 56 is for offsetting the address of the adder 55 by the reset signal and the line synchronization signal from the comparator 53. The comparator 57 includes an offset row address register 56.
Is compared with the address of the address counter 59, and when the address of the address counter 59 is one before the offset address, a write signal is output to the address counter 59.

The row start address register 58 is set with the address from the offset row address register 56 every time the line synchronization signal is supplied. The address counter 59 sets the start address from the start address register 58 of the row according to the write signal from the comparator 57, counts up this address value each time the image clock is supplied, and outputs it as a dither threshold address. To do.

The present invention is not limited to the above embodiment. For example, as the feedback type method, not only the error diffusion method but also another feedback type gradation processing method having a line memory or the like is used. Further, as the error filtering means, a filter using a random coefficient or a filter having a shape different from the shape described in the embodiment may be considered. As for the threshold value generation unit, a configuration such as a threshold value generation unit using various buses can be considered as described above.

As described above, in the feedback type gradation processing method, the tissue dithering or the simple multi-valued processing can be implemented by one configuration. With this configuration, the error buffer (line buffer) often used in the feedback type can be used also as the dither matrix threshold buffer, so that the size, shape, and threshold of the dither matrix can be freely set. Therefore, flexible dither processing is also possible.

Further, in the image processing apparatus using the error diffusion, a structure that enables tissue dithering, simple gradation processing, etc. is proposed, and the advantages of each processing are utilized by switching the processing methods as needed. You can do whatever you want.

Further, in the gradation processing using feedback such as error diffusion, the tissue dither processing is provided by providing the feedback control means for controlling the error feedback and the correction amount feedback and the threshold generation means for switching the threshold. Is also possible.

Further, in feedback type gradation processing such as error diffusion, a means for sharing the error buffer with the systematic dither threshold buffer and a buffer control means for carrying out shared buffer control according to the processing are provided.

Further, a RAM is used as a dither threshold buffer.
The threshold value setting means for arbitrarily setting the dither size, the shape, the threshold value, and the like, and the threshold value reading control means for reading according to the set threshold size, shape, etc.

Therefore, in the gradation processing method based on the error feedback method, tissue dither, simple gradation processing, etc. can be implemented by one configuration, and the error buffer used for the error feedback processing is the dither threshold buffer during dither processing. The error feedback process, the tissue dither, or the simple gradation process can be realized by using this as a single configuration, and by using this configuration, the size, shape, and threshold value of the dither matrix can be freely set, which is flexible. It is possible to perform dither processing with a certain amount.

[0071]

As described above in detail, according to the present invention,
In a system that has a gradation processing method based on the error diffusion method based on the feedback type, it is possible to perform gradation processing using the systematic dither method, and by switching to the error diffusion method or the systematic dither method as necessary, both It is possible to provide an image processing apparatus capable of performing flexible processing because the size, shape, and setting of the dither threshold can be freely set by utilizing this advantage.

[Brief description of drawings]

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

FIG. 2 is a diagram for explaining the selection contents of a gradation processing method.

FIG. 3 is a diagram showing a configuration of an image processing apparatus when a binary error diffusion method is used.

FIG. 4 is a diagram showing corrected image data.

FIG. 5 is a diagram showing a configuration of a comparison unit.

FIG. 6 is a diagram showing a configuration of a comparison unit.

FIG. 7 is a diagram showing a configuration of a comparison unit.

FIG. 8 is a diagram showing a binarization error amount.

FIG. 9 is a diagram showing a configuration of a switching unit.

FIG. 10 is a diagram showing a configuration of an error filter and a correction amount calculation unit.

FIG. 11 is a block diagram showing a configuration of a memory interface.

FIG. 12 is a block diagram showing a configuration of a dither threshold address generator.

FIG. 13 is a principle diagram of conventional binary error diffusion.

FIG. 14 is a diagram showing the principle of binarization by the conventional tissue dither.

[Explanation of symbols]

1 ... Error correction means, 2 ... Comparison means, 3 ... Output value calculation means, 4 ... Error calculation means, 5 ... Switching means, 6 ... Error filtering means, 7 ... Processing instruction means, 8 ... Processing control section, 1
0 ... Line memory, 12 ... Threshold value generating means, 13 ... Correction amount calculating means, 14 ... Switching means.

Claims (2)

[Claims] 1. A multi-valued device for supplying image data represented by a plurality of bits per pixel to a target pixel and peripheral pixels, and comparing the image data supplied by this supplying device with a predetermined threshold value. Conversion means for converting into multi-valued data to be converted, calculation means for calculating the error in pixel units by the multi-valued data from the multi-valued means and the image data from the supply means, and the calculation means First processing means for diffusing the calculated error in pixel units to the peripheral pixels of the pixel of interest, an error buffer for storing a part of the error diffusion amount diffused by the first processing means, and this error A correction amount calculation means for calculating a correction amount using a part of the error diffusion amount stored in the buffer and the other part of the error diffusion amount diffused by the processing means, and the correction amount calculation means. In the image processing device, a correction unit that corrects the image data of the pixel of interest from the supply unit based on the calculated correction amount, an instruction unit that instructs whether to use the error diffusion method or the tissue dither, and a tissue dither Setting means for setting the contents of the tissue dither in the error buffer, and when the tissue dither is instructed by the instructing means, the calculation unit outputs the error in pixel units to the first processing unit. Prohibition means for prohibiting the output of the correction amount from the correction amount calculation means to the correction means, and an output for sequentially outputting each data of the tissue dither stored in the error buffer as a threshold value to the conversion means. An image processing device comprising: 2. The image processing apparatus according to claim 1, wherein the content of the tissue dither set by the setting unit is a dither size, a shape, and a threshold value.