JP3737582B2 - Image forming apparatus and image forming method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus and an image forming method for receiving image data transmitted through a public line and forming an image based on the received image data on an image forming medium such as a cut sheet. .
[0002]
[Prior art]
A so-called facsimile apparatus that transmits image data obtained by scanning a document image via a public line, or receives image data via a public line and forms an image based on the received image data. It has been known.
[0003]
Here, a case will be described in which received image data defined in the main scanning direction and the sub-scanning direction is output to a standard size recording sheet such as a cut sheet by such a facsimile apparatus. First, received image data is temporarily stored in a receiving image memory. When the received image data stored in the reception image memory is output, as a first step, the size of the recording paper on which the received image data is output is determined. The size of the recording paper, for example, A3, B4, B5, etc. is determined based on the size data in the main scanning direction of the received image data included in the received image data (the size of the received image data in the sub-scanning direction). Is not related to the size determination of the recording paper). Next, as a second stage, the number of image lines in the sub-scanning direction of the received image data stored in the reception image memory is counted for each single page, and this received image data determined in the first stage is counted. Is compared with the number of effective recording lines of the recording paper that outputs the data, and output processing is performed according to the comparison result.
[0004]
For example, normal processing for outputting a single page as it is if the number of image lines in the sub-scanning direction in the received image data of a single page is within the number of effective recording lines, or a single page if the number of image lines is larger than the number of effective recording lines A part of the received image data (the amount exceeding the number of effective recording lines) is cut off and output as a single page, and the received image data is reduced in the sub scanning direction and output as a single page. Various output processes such as a process of dividing the received image data into a plurality of pages in the sub-scanning direction and outputting each of the divided received image data as a single page are performed.
As the above-described reduction processing, reduction processing by thinning out image lines described in Japanese Patent Application No. 5-46746 is known as a known technique.
[0005]
[Problems to be solved by the invention]
However, according to the above-described image line decimation process, a specific image line is thinned out (ignored) from the received image data received and printed out, so that the received image data received is sufficiently reflected. (Thinned image lines are not reflected). In such a case, when an image formed based on the received image data (original image data) received is compared with an image formed based on the received image data after the reduction process, the latter image is obtained. You may find that chipping has occurred.
[0006]
For example, if one line is thinned out from image data formed with five lines in the sub-scanning direction, the image data is reduced to 4/5, but the thinned image data disappears. In addition, when the image is output at a low resolution, such a lack of image appears more remarkably.
[0007]
An object of the present invention has been made in view of the above-described circumstances, and is capable of preventing image quality deterioration due to image data reduction processing executed when a long document is output to a predetermined cut sheet. An apparatus and an image forming method are provided.
[0008]
[Means for Solving the Problems]
This invention has been made based on the above problems,
According to this invention,
Receiving means for receiving image data defined in the main scanning direction and the sub-scanning direction;
The number of image lines in the sub-scanning direction in the received image data of a single page received by the receiving means is compared with the number of effective recording lines of the image forming medium that is the output destination of the received image data. And a resolution enlarging means for enlarging the reception resolution in the sub-scanning direction in the received image data to n times the predetermined reduction ratio,
An image forming means for forming an image based on the received image data after the resolution enlargement by the resolution enlargement means on the image forming medium at a resolution n times the reception resolution;
An image forming apparatus is provided.
[0009]
Moreover, according to this invention,
Receiving means for receiving image data defined in the main scanning direction and the sub-scanning direction;
The number of image lines in the sub-scanning direction in the received image data of a single page received by the receiving means is compared with the number of effective recording lines of the image forming medium that is the output destination of the received image data. When the number of image lines in the direction is a predetermined number or more greater than the number of effective recording lines, the reception resolution is constant with respect to the sub-scanning direction so that the reception resolution in the sub-scanning direction of the received image data is n times the predetermined reduction ratio. Means for enlarging the resolution at intervals,
An image forming means for forming an image based on the received image data after the resolution enlargement by the resolution enlargement means on the image forming medium at a resolution n times the reception resolution;
An image forming apparatus is provided.
[0010]
Furthermore, according to the present invention,
Receiving means for receiving image data defined in the main scanning direction and the sub-scanning direction;
The number of image lines in the sub-scanning direction in the received image data of a single page received by the receiving means is compared with the number of effective recording lines of the image forming medium that is the output destination of the received image data. When the number of image lines in the direction is greater than the number of effective recording lines by a predetermined number or more and the reception resolution in the sub-scanning direction of the received image data is lower than the predetermined resolution, the resolution enlargement is performed to enlarge the reception resolution to n times the predetermined reduction ratio. Means,
The number of image lines in the sub-scanning direction in the received image data of a single page received by the receiving means is compared with the number of effective recording lines of the image forming medium that is the output destination of the received image data. When the number of image lines in the direction is a predetermined number or more larger than the number of effective recording lines and the reception resolution in the sub-scanning direction in the received image data is higher than the predetermined resolution, the number of image lines in the sub-scanning direction in the received image data is Thinning processing means for thinning out a predetermined number of image lines from the received image data so as to be equal to or less than the number of effective recording lines;
A first image forming process for forming an image based on the received image data whose resolution has been enlarged by the resolution enlarging means on the image forming medium at a resolution n times the receiving resolution, and reception after the thinning process by the thinning means Image forming means for executing a second image forming process for forming an image based on image data on the image forming medium;
An image forming apparatus is provided.
[0011]
Furthermore, according to the present invention,
Receiving means for receiving image data defined in the main scanning direction and the sub-scanning direction;
The number of image lines in the sub-scanning direction in the received image data of a single page received by the receiving means is compared with the number of effective recording lines of the image forming medium that is the output destination of the received image data. And a truncation means for truncating a predetermined number of image lines from the received image data of this single page,
The number of image lines in the sub-scanning direction in the received image data of a single page received by the receiving means is compared with the number of effective recording lines of the image forming medium that is the output destination of the received image data. And a resolution enlarging means for enlarging the reception resolution in the sub-scanning direction in the received image data of the single page to n times a predetermined reduction ratio,
The number of image lines in the sub-scanning direction in the received image data of a single page received by the receiving means is compared with the number of effective recording lines of the image forming medium that is the output destination of the received image data. According to the dividing means for dividing the received image data of the single page into a plurality of pages,
A first image forming process for forming an image based on the received image data after the truncating process by the truncating unit on the image forming medium; and an image based on the received image data after the resolution enlarging by the resolution enlarging unit a second image forming process formed on the image forming medium with a resolution of n times, and a third image forming process for forming an image based on the received image data after the dividing process by the dividing unit on the image forming medium. Image forming means for executing
An image forming apparatus is provided.
[0012]
Still further, according to the present invention,
Receiving means for receiving image data defined in the main scanning direction and the sub-scanning direction;
The number of image lines in the sub-scanning direction in the received image data of a single page received by the receiving means is compared with the number of effective recording lines of the image forming medium that is the output destination of the received image data. When the number of image lines in the direction is greater than the number of effective lines and less than or equal to the first threshold value, truncation means for truncating image lines exceeding the number of effective lines from the received image data of the single page;
The number of image lines in the sub-scanning direction in the received image data of a single page received by the receiving means is compared with the number of effective recording lines of the image forming medium that is the output destination of the received image data. Resolution enlarging means for enlarging the reception resolution in the sub-scanning direction in the received image data of this single page to n times a predetermined reduction ratio when the number of image lines in the direction is greater than the first threshold and less than or equal to the second threshold. ,
The number of image lines in the sub-scanning direction in the received image data of a single page received by the receiving means is compared with the number of effective recording lines of the image forming medium that is the output destination of the received image data. Dividing means for dividing the received image data of the single page into a plurality of pages when the number of image lines in the direction is larger than the second threshold;
A first image forming process for forming an image based on the received image data after the truncating process by the truncating unit on the image forming medium; and an image based on the received image data after the resolution enlarging by the resolution enlarging unit a second image forming process formed on the image forming medium with a resolution of n times, and a third image forming process for forming an image based on the received image data after the dividing process by the dividing unit on the image forming medium. Image forming means for executing
An image forming apparatus is provided.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of an image forming apparatus, that is, a facsimile machine according to an embodiment of the present invention.
[0014]
As shown in FIG. 1, the image forming apparatus 1 is provided with a main CPU 10 and a FAX CPU 20, both of which are connected by an expansion I / F 30.
[0015]
The main CPU 10 controls the entire image forming apparatus 1, and an operation panel unit 11, a nonvolatile memory 12, a mechanical control unit 13, and an image processing unit 14 are connected to the main CPU 10. The operation panel unit 11 receives various operations from the user. The operation panel unit 11 is provided with a display unit 11a. The display unit 11a displays information such as the state of the image forming apparatus or various operation methods. Various configurations are stored in the nonvolatile memory 12. The mechanical control unit 13 controls each mechanism operation in the scanner unit 15 and the printer unit 16. The image processing unit 14 performs digital image processing such as various correction processing and filtering processing on the image data acquired by the scanner unit 15 or the MODEM 21.
[0016]
The FAX CPU 20 implements a facsimile function in response to an instruction from the main CPU 10 via the extended I / F 30. The FAX CPU 20 includes a MODEM 21, an NCU 22, a page memory 23, a code memory 24, a code / decoding IC 25, and a code / decoding IC 25. A decryption IC 26 and the like are connected. The MODEM 21 is a modem for transmitting and receiving image data to and from an analog telephone line. The NCU 22 is a telephone network control circuit for connecting to an analog telephone line. The page memory 23 is for temporarily storing image data when outputting the image data. The encoding / decoding ICs 25 and 26 are for encoding, decoding, or binary compressing image data. Further, the encoding / decoding IC 25 counts the number of image lines in the sub-scanning direction of the received image data received for each single page. The encoding / decoding IC 26 performs a truncation process, a reduction process, a division process, and the like, which will be described later. The code memory 24 is for storing the compressed data binary-compressed in the code / decoding ICs 25 and 26. Note that the reduction processing may be performed by the FAX CPU 20.
[0017]
Here, the image data reception / output operation by the image forming apparatus configured as described above will be briefly described. First, image data defined in the main scanning direction and the sub-scanning direction as shown in FIG. 2 is received by the image forming apparatus via the communication line, the NCU 22, and the MODEM 21. The received image data received is decoded by the encoding / decoding unit 25. At this time, the number of image lines in the sub-scanning direction in the received image data is counted for each single page of received image data, encoded again, and temporarily stored in the code memory 24. At this time, the FAX CPU 20 accesses the encoding / decoding IC 25 and recognizes the number of image lines for each single page of the received image data. The received image data stored in the code memory 24 is decoded by the code / decoding IC 26. The decoded received image data is subjected to various output processes according to the number of image lines as necessary, for example, a truncation process, a reduction process, or a division process, and the printer unit via the image processing unit. 16 is output.
[0018]
Further, the various output processes described above will be described here. As described in the related art, based on the size data in the main scanning direction included in the received image data, the size (A3, B4, A4, etc.) of the recording paper (cut sheet) that is the output destination of the received image data is determined. It is determined. Therefore, when a long document (document that is long in the sub-scanning direction) is received image data, the entire received image data may not be output to the output destination recording paper. In order to compensate for this, various output processes are executed. The determination as to whether or not to execute these various output processes is performed by comparing the number of image lines in the sub-scanning direction of the received image data with the number of effective recording lines that can be printed on the recording paper that is the output destination of the received image data. , Based on the result of this comparison. For example, the number of image lines in the sub-scanning direction of the received image data is M, and the number of effective recording lines that can be printed on the recording paper that is the output destination of the received image data is P (the value of P differs depending on the size of the recording paper). Then, various output processes are executed under the following conditions.
[0019]
When the number M of image lines in the sub-scanning direction of the received image data of a single page is less than or equal to the effective recording line number P of the recording paper to which the received image data is output (M ≦ P), the received image data is based on the received image data. The processed image is normally output as it is on the recording paper. The normal output is a process for outputting an image based on image data at the same magnification without performing any output process. In the case of the condition (M ≦ P), the entire image based on the received image data can be formed on the recording paper by normal output.
[0020]
The number M of image lines in the sub-scanning direction of the received image data of a single page is larger than the number of effective recording lines P of the recording paper that is the output destination of the received image data, and the first threshold (for example, the number of effective recording lines P + predetermined) If the threshold value (10 [mm]) or less (P <M ≦ first threshold value (P + 10 [mm])), truncation processing is executed. Here, it is shown that the truncation process is executed when the size of the received image data of a single page in the sub-scanning direction is slightly larger than the recording paper (10 [mm] or less). In general, the edge portion of a document image is often blank. Using this fact, when the size of the received image data of a single page is slightly larger than the recording paper, the larger portion is cut off from the received image data and printed. That is, the truncation process is a process of truncating the number of image lines that exceeds the number of effective recording lines from the received image data. FIG. 3 shows an image of this truncation process.
[0021]
The number M of image lines in the sub-scanning direction of the received image data of a single page is greater than the first threshold value, for example, P × (1 / 0.9 (reduction ratio (90%) in the sub-scanning direction). = P × 1.1) or less (first threshold (P + 10 [mm]) <M ≦ second threshold (P × 1.1)), the reduction processing of the received image data in the sub-scanning direction is executed. An image of the reduction process is shown in Fig. 4. The reduction process is a point of the present invention, and the specific processing contents will be described in detail later.
[0022]
When the number M of image lines in the sub-scanning direction of the received image data of a single page is larger than the second threshold (second threshold (P × 1.1) <M), the division process is executed. Here, it is shown that the division process is executed when the size of the received image data of a single page in the sub-scanning direction is significantly larger than the recording paper. This division process is a process of dividing the received image data in units of the effective recording line number P of the recording paper that is the output destination of the received image data. Is output as FIG. 5 shows an image of this division processing.
[0023]
It should be noted that the numerical values described as the execution conditions for each of the output processes described above are all examples and are variable depending on the settings of the image forming apparatus.
Next, the reduction process that is the point of the present invention will be described in detail. FIG. 6 is an image diagram of received image pixels of 6 dots in the main scanning direction and 6 lines in the sub-scanning direction. The following description proceeds with the received image shown in FIG. 6 as an original image.
[0024]
When the conventional reduction processing, that is, reduction processing by thinning, is performed on the received image of FIG. 6, an image as shown in FIG. 7 is obtained. In the image of FIG. 7, since the third line of the received image is reduced and reduced, the received image is not sufficiently reflected during printing (the third line of the received image is not reflected).
[0025]
Therefore, in the present invention, the reception resolution in the sub-scanning direction of the received image data is enlarged to n times the predetermined reduction rate, and an image based on the received image data after the resolution enlargement is output at a resolution n times the reception resolution. Thus, reduction of the received image is realized. First, resolution expansion will be described. FIG. 8 is an image diagram showing a state in which the reception resolution in the sub-scanning direction of the received image is enlarged (180% enlarged) to n times (2 times) a predetermined reduction ratio (90%). In FIG. 8, only the fifth line is an original image whose resolution is not enlarged. In the resolution enlargement process, first, the number of image lines in the sub-scanning direction of the received image data of a single page is compared with the number of effective recording lines of the recording paper that is the output destination of the received image data. The reduction ratio (90%, 95%, etc.) is determined in accordance with the number of image lines in excess of the number. The reception resolution of the received image data is enlarged at regular intervals in the sub-scanning direction by the encoding / decoding IC 26 so as to be n times the determined reduction ratio, and the state shown in FIG. 8 is obtained.
[0026]
FIG. 9 is an image diagram showing a state in which the image data whose reception resolution is enlarged n times the reduction rate as shown in FIG. 8 is output at a resolution n times the reception resolution. That is, the reduced-size printing of the received image is performed by printing the image data whose resolution has been enlarged at a resolution equivalent to the resolution after the resolution has been enlarged. As a printing method corresponding to the resolution whose resolution is enlarged, when printing at a high resolution, the printing is performed by narrowing the dot pitch at the time of printing as compared with the case of a low resolution. Therefore, in FIG. 9, the portion of the fifth line is reduced and printed as compared with the original image. By such a reduction process, the original image data can be reduced without erasing the original image data.
[0027]
Here, the above-described magnification n will be described. This magnification n is set in advance to a predetermined value (for example, magnification 2). However, it is possible to make the best use of the performance of the printer 16 by setting the magnification n to the following set value. That is, when the reception resolution of the received image data is enlarged to n times the predetermined reduction ratio, and the image data after the enlargement process is output at a resolution that is n times the reception resolution, the resolution that is n times the reception resolution is the printer. The magnification n is set so that output is possible with the performance of the output resolution. Thereby, the output resolution of the printer 16 can be utilized to the maximum extent.
[0028]
Further, two specific examples of resolution enlargement with limited numerical values will be described here. The first is a case where image data received at a receiving resolution of 3.85 lines / mm in the sub-scanning direction is enlarged to an arbitrary X% and printed at an output resolution of 7.7 lines / mm. The second is a case where image data received at a receiving resolution of 7.7 lines / mm in the sub-scanning direction is enlarged to an arbitrary X% and printed at an output resolution of 15.4 lines / mm. “X” is a reduction ratio determined in advance according to the difference between the number of image lines in the sub-scanning direction of the received image data of a single page and the number of effective recording lines of the recording paper that is the output destination of the received image data. The value is approximately doubled and is in the range of 180 to 199.
[0029]
A further specific example when the resolution is enlarged to an arbitrary X% will be described. For example, the reduction ratio at the time of reduced printing in the sub-scanning direction is 90%, the number of image lines in the sub-scanning direction of the received image data of a single page is 1265 lines, and the effective recording line of the recording paper that is the output destination of this received image data The number is 1150 lines. In this case, since “X” is 180%, which is twice 90%, the number of image lines 1265 is enlarged by 180% and the number of image lines is 2277 lines. At the time of printing, since it is printed with a resolution equivalent to twice the reception resolution, that is, 2277/2 = 1139 lines, the received image data has been reduced by 90%.
[0030]
Next, image output processing by the image forming apparatus shown in FIG. 1 will be described with reference to the flowchart of FIG.
First, the setting of the truncation process, the reduction process, and the division process in the image forming apparatus is turned on (ST10, ST12, ST14). Thereby, truncation processing, reduction processing, and division processing are executed according to the conditions. In the image forming apparatus, reception of image data is started (ST16), and when reception of image data ends normally (ST18), output processing of the received received image data is subsequently executed.
[0031]
Here, M is the number of image lines in the sub-scanning direction of the received image data of a single page, P is the number of effective recording lines of the recording paper that is the output destination of the received image data, and the resolution is enlarged n times the predetermined reduction ratio. Let X be the rate.
[0032]
The number M of image lines in the sub-scanning direction of the received image data of a single page is larger than the number of effective recording lines P of the recording paper that is the output destination of the received image data, and the first threshold (for example, the number of effective recording lines P + predetermined) If the threshold value (10 [mm]) or less (P <M ≦ first threshold value (P + 10 [mm])) (ST20, YES), the truncation process is executed (ST22). Then, printing is executed based on the received image data subjected to the truncation process (ST24).
[0033]
The number M of image lines in the sub-scanning direction of the received image data of a single page is greater than the first threshold value, for example, P × (1 / 0.9 (maximum reduction ratio (90%) in the sub-scanning direction). ) = P × 1.1) or less (first threshold value (P + 10 [mm]) <M ≦ second threshold value (P × 1.1)), the reduction processing in the sub-scanning direction of the received image data is executed. (ST26, YES) In this case, a reduction process according to the reception resolution is executed.
[0034]
One example will be described. When the reception resolution is 3.85 lines / mm (ST28, YES), the resolution is arbitrarily enlarged to X% (ST30), and printing is performed at a resolution of 7.7 lines / mm (ST32). . When the reception resolution is 7.7 lines / mm (ST34, YES), the resolution is arbitrarily enlarged to X% (ST36), and printing is executed at a resolution of 15.4 lines / mm (ST38). . When the reception resolution is 15.4 lines / mm (ST40, YES), reduction processing is performed by thinning and printing is performed (ST42). The reason why the reduction process is changed in accordance with the reception resolution in this way is that the performance of the output resolution in the printer 16 of the image forming apparatus 1 is limited. That is, when the received image data can be output at a resolution n times the reception resolution, a reduction process is performed by the resolution enlargement process, and when the received image data cannot be output at a resolution n times the reception resolution, thinning is performed. This means that the reduction process is executed.
[0035]
When the number M of image lines in the sub-scanning direction of the received image data of a single page is larger than the second threshold (second threshold (P × 1.1) <M) (ST44, YES), division processing Is executed (ST46). Then, printing is executed based on the received image data subjected to the truncation process (ST48).
[0036]
When the number M of image lines in the sub-scanning direction of the received image data is less than or equal to the effective number of recording lines P of the recording paper that is the output destination of the received image data (M ≦ P) (ST50, YES), the received image data The image based on is printed on the recording sheet as it is (ST52).
[0037]
【The invention's effect】
According to the present invention, it is possible to provide an image forming apparatus and an image forming method capable of realizing a reduction process with little deterioration in image quality as compared with a reduction process using conventional thinning.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the invention.
FIG. 2 is an image diagram of image data defined in a main scanning direction and a sub-scanning direction.
FIG. 3 is an image diagram of truncation processing.
FIG. 4 is an image diagram of reduction processing.
FIG. 5 is an image diagram of division processing.
FIG. 6 is a diagram showing a received image (original image).
FIG. 7 is a diagram showing a received document after thinning processing.
FIG. 8 is a diagram showing a received document after resolution enlargement processing;
FIG. 9 is a diagram illustrating a state in which a received document after resolution enlargement processing is printed at a resolution equivalent to that after resolution enlargement.
FIG. 10 is a flowchart showing image data output processing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 10 ... Main CPU
DESCRIPTION OF SYMBOLS 11 ... Operation panel part 12 ... Nonvolatile memory 13 ... Mechanical control part 14 ... Image processing part 15 ... Scanner 16 ... Printer 20 ... FAXCPU
21 ... MODEM
22 ... NCU
23: Page memory 24: Code memory 25, 26: Code / decoding IC

Claims (3)

Receiving means for receiving image data defined in the main scanning direction and the sub-scanning direction;
Compares the number of image lines in the sub-scanning direction in the received image data of a single page which has been received by the receiving means, and an effective recording speed line of the output destination becomes an image forming medium of the received image data, the sub-scan When the number of image lines in the direction is greater than the number of effective lines and less than or equal to the first threshold value, truncation means for truncating image lines exceeding the number of effective lines from the received image data of the single page;
The number of image lines in the sub-scanning direction in the received image data of a single page received by the receiving means is compared with the number of effective recording lines of the image forming medium that is the output destination of the received image data. When the number of image lines in the direction is greater than the first threshold and less than or equal to the second threshold, and the reception resolution in the sub-scanning direction of the received image data is the first resolution, the sub-scanning direction in the received image data of this single page Resolution enlarging means for enlarging the receiving resolution of the image to n times the predetermined reduction rate
The number of image lines in the sub-scanning direction in the received image data of a single page received by the receiving means is compared with the number of effective recording lines of the image forming medium that is the output destination of the received image data. When the number of image lines in the direction is greater than the first threshold and less than or equal to the second threshold and the reception resolution in the sub-scanning direction of the received image data is a second resolution higher than the first resolution, the sub-line in the received image data is Thinning processing means for thinning out a predetermined number of image lines from the received image data so that the number of image lines in the scanning direction is equal to or less than the number of effective recording lines;
The number of image lines in the sub-scanning direction in the received image data of a single page received by the receiving means is compared with the number of effective recording lines of the image forming medium that is the output destination of the received image data. Dividing means for dividing the received image data of the single page into a plurality of pages when the number of image lines in the direction is larger than the second threshold;
A first image forming process for forming an image based on the received image data after the truncating process by the truncating unit on the image forming medium; and an image based on the received image data after the resolution enlarging by the resolution enlarging unit a second image forming process for forming on the image forming medium with a resolution of n times; a third image forming process for forming an image based on the received image data after the thinning process by the thinning unit on the image forming medium; And image forming means for executing a fourth image forming process for forming an image based on the received image data after the dividing process by the dividing means on the image forming medium;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the magnification n in the resolution enlarging unit is set according to the performance of the output resolution in the sub-scanning direction of the image forming unit.   Receiving image data defined in the main scanning direction and the sub-scanning direction;
  The number of image lines in the sub-scanning direction in the received image data of the received single page is compared with the number of effective recording lines of the image forming medium that is the output destination of the received image data.
  When the number of image lines in the sub-scanning direction is greater than the number of effective lines and less than or equal to the first threshold value, the number of image lines exceeding the number of effective lines is rounded down from the received image data of the single page.
  When the number of image lines in the sub-scanning direction is greater than the first threshold value and less than or equal to the second threshold value, and the reception resolution in the sub-scanning direction in the received image data is the first resolution, the received image data in the single page Enlarge the reception resolution in the sub-scanning direction to n times the predetermined reduction rate,
  When the number of image lines in the sub-scanning direction is greater than the first threshold and less than or equal to the second threshold and the reception resolution in the sub-scanning direction of the received image data is a second resolution higher than the first resolution, the received image A predetermined number of image lines are thinned out from the received image data so that the number of image lines in the sub-scanning direction in the data is equal to or less than the number of effective recording lines.
  When the number of image lines in the sub-scanning direction is larger than the second threshold value, the received image of this single page Divide the data into multiple pages,
  A first image forming process for forming an image based on the received image data after the truncation process on the image forming medium; an image based on the received image data after the resolution is enlarged; A second image forming process formed on the medium, a third image forming process for forming an image based on the received image data after the thinning process on the image forming medium, and an image based on the received image data after the dividing process. Performing any of the fourth image forming processes formed on the image forming medium;
  An image forming method.

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