JPH0851541A - Image processor and its method - Google Patents

Abstract

PURPOSE:To obtain an output image with a proper density independently of resolution or the like when image data are outputted and to prevent deterioration in the image quality attended with converted resolution. CONSTITUTION:Image data read by a contact sensor section 101 in the case of copying are converted into desired density data by a luminance-density conversion table 104, a resolution conversion section A105 applies resolution conversion to the data in matching with the resolution of an ink jet printer 110 and an error propagation processing section 106 binarizes the data by the error propagation method and the image data subject to binarization are outputted by the ink jet printer 110. A luminance-density conversion table 104 is a table to decide a density characteristic of image data received based on prescribed pattern data.

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 and method for processing input image data, and more particularly to an image processing apparatus and method for obtaining an image of good quality.

[0002]

2. Description of the Related Art Conventionally, according to the G3 facsimile standard, the scanning line density for reading and recording is 8 dots / mm in the main scanning direction and 3.
85 line / mm (standard), 7.7 line
/ Mm (fine) and 15.4 line / mm (super fine).

Therefore, most of the conventional facsimile machines adopt the method corresponding to the above-mentioned scanning line density for both the reading means and the recording means. Particularly, regarding the recording means, the control is easy and the space is reduced. Most of them used the thermal recording method.

However, since heat-sensitive recording paper cannot be preserved due to fading and cannot be retouched, the use of plain paper for recording paper is rapidly prevailing today.

In this case, the plain paper recording method is L
The BP (laser beam printer) system and the inkjet system are generally used. However, in these LBP and inkjet recording devices, the resolution is about 400 dpi, which is much higher than the scanning line density of the G3 standard. When performing the above, or when performing the copy recording of the read original, the resolution of the image data must be converted and recorded according to the resolution of the recording apparatus. Hereinafter, this specific example will be described.

FIG. 6 is a block diagram showing a conventional plain paper recording facsimile apparatus.

In FIG. 6, reference numeral 601 denotes a contact sensor section (CS) for reading an original image. In this conventional example apparatus, the main scanning direction is 8 dots / mm, and the sub-scanning direction is, for example, 7 depending on the original conveyance pitch. It is a CS for a facsimile that reads at a resolution of 0.7 line / mm or the like.

Reference numeral 602 denotes an analog image processing unit for performing analog image processing such as direct current reproduction and shading correction on the analog output of the CS 601; and 603, a multi-value level (for example, 64) digital output of the analog image processing unit 602 for each pixel. It is an A / D converter that converts the data.

Reference numeral 604 is a brightness-density conversion table section for LOG converting the brightness data of each pixel output from the A / D conversion section 603 into density data, and 605 is a multi-value output of the brightness-density conversion table section 604. An error diffusion processing unit that performs halftone processing on data by an error diffusion method to generate binarized image data.

In the error diffusion processing here, the pixel of interest is binarized using the error diffusion matrix shown in FIG. As is well known in the art, this error diffusion processing binarizes input multi-valued pixel data with a predetermined threshold value and two-dimensionally diffuses the error from the threshold value according to the weighting coefficient of the error diffusion matrix. It is something that goes. As a result, the density of the entire image can be preserved, a pseudo halftone image can be obtained, and a smooth, visually beautiful halftone image can be obtained by spreading in two dimensions. You can

A data control unit 606 controls transfer of image data according to each mode of transmission, reception, and copying.
Reference numeral 07 denotes a resolution conversion unit for converting the resolution of the image data into the resolution of the printer when the image data is printed and recorded.
Reference numeral 08 denotes a density correction unit for performing density correction on the image data whose resolution has been converted by the resolution conversion unit 607.
Reference numeral 9 is an ink jet printer for printing and recording at high resolution. In the conventional example device, the resolution is 360 dpi × 360 dpi.
I am using a printer.

Reference numeral 610 is a modem for modulating / demodulating image data at the time of transmission / reception, 611 is an NCU for controlling the station line at the time of transmission / reception, and 612 is a C for controlling the above-mentioned parts.
It is PU.

Next, the operation of the conventional apparatus will be described below.

First, in the transmission mode, the transmission document is read by the CS 601 at a resolution of 8 dots / mm in the main scanning direction and, for example, 7.7 line / mm in the sub-scanning direction by the operator's selection, and the output is the analog image processing unit 602.
Is corrected in step A and converted into multi-value digital data per pixel in the A / D converter 603.

This data is stored in the luminance-density conversion table section 6
In step 04, the density data is LOG-converted, and the error diffusion processing unit 6
In 05, binarization processing is performed and image data is output. In the conventional apparatus, the image data obtained here has a resolution of 8 dots / mm in the main scanning direction and 7.7 line / mm in the sub-scanning direction.

This image data is sent to the modem 610 by the data control unit 606, modulated into an analog transmission signal, and sent to the local line through the NCU 611.

Next, in the reception mode, the analog transmission signal coming from the station line is sent to the modem 610 through the NCU 611 and demodulated into digital image data. This resolution is G3 standard and 8 dots / mm in the main scanning direction. Is. It is assumed that data of 7.7 line / mm is received in the sub-scanning direction.

The data control unit 606 transfers this image data to the resolution conversion unit 607 and converts the resolution of the image data.

That is, 8 dots / mm × 7.7 lin
In order to record the data of e / mm by the inkjet printer 609 of 360 dpi × 360 dpi, the predetermined number of pixels of the image data is increased so as to increase the number of pixels by about 1.77 times in the main scanning direction and about 1.84 times in the sub scanning direction. Pixels are added according to the pattern.

In the ink jet system, the recorded image becomes too dark when viewed as an entire image compared to the actual original image due to ink bleeding or the like.

Therefore, in order to prevent the image density when printed by the ink jet printer 609 from becoming visually dark due to the increase in the number of pixels due to the above-described resolution conversion, the density correction unit 608 sets black pixels to white pixels in accordance with the pattern of the image data. Density correction is performed by substituting pixels.

This data is stored in the ink jet printer 60.
9 and the image is recorded with a resolution of 360 dpi × 360 dpi.

Next, in the copy mode, the original image read by the CS 601 is processed in the same manner as in the transmission mode and is binarized image data, for example, 8 dots / mm × 7.7 l.
It is obtained from the error diffusion processing unit 605 with a resolution of ine / mm.

This image data is transferred to the resolution conversion unit 607 by the data control unit 606.

Further, this image data is 8 dots / mm × 7.7 lin in the resolution conversion unit 607 as in the reception mode.
The resolution is converted from e / mm to 360 dpi × 360 dpi, and as in the case of the recording of the reception data described above,
In order to prevent the image as a whole from becoming too dark, the density correction unit 608 reverses from black pixels to white pixels, and then the inkjet printer 609 performs 360 dpi × 360.
An image is recorded at a resolution of dpi.

[0026]

However, in the above-mentioned conventional apparatus, the resolution of the data after being binarized by the error diffusion process is converted. That is,
In the copy mode, for example, 8 dots / mm × 7.7
Image data read in line / mm is binarized by error diffusion processing, and an image processing pattern obtained by adding pixels is added to the image processing pattern for resolution conversion into the printer resolution of 360 dpi × 360 dpi. Pixels were replaced in order to correct the density as a whole. Therefore, after reading the original image, the image processing pattern (smooth halftone image) obtained by the error diffusion processing is destroyed by these pixel operations, and the output image is significantly deteriorated as compared with the original image. Was there. Further, the pixel replacement process as described above becomes complicated.

Further, since the algorithm for brightness-density conversion usually has only one pattern, density correction depending on the resolution of input image data or output image data cannot be properly performed. Further, if the processing method before the resolution conversion is different, the apparent density of the image as a whole looks different even if the resolution is the same.

These problems have been very problematic because the importance of the copy function is increasing in the above-mentioned standardization of recording paper.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an image processing apparatus and method capable of obtaining an output image having an appropriate density regardless of the output resolution.

Another object of the present invention is to provide an image processing apparatus and method capable of preventing deterioration of image quality due to resolution conversion.

[0031]

To achieve the above object, the image processing apparatus of the present invention has the following configuration.

That is, the image processing apparatus of the present invention outputs the image data at a predetermined resolution, the input means for inputting the image data, the data conversion means for converting the density characteristic of the image data input by the input means. And output means.

In the above arrangement, the data converting means converts the density characteristic so that the density is almost the same even if the resolution of the image data output by the output means is different.

Further, the image processing apparatus of the present invention comprises input means for inputting image data, data conversion means for converting density characteristics of the image data input by the input means, and an image converted by the data conversion means. Resolution conversion means for converting the resolution of the data to a predetermined resolution, halftone processing means for performing halftone processing on the image data converted by the resolution conversion means, and image data halftone processed by the halftone processing means. It has an output means for outputting at the predetermined resolution.

In the above structure, the data converting means converts the density characteristic so that the density of the image data input by the input means becomes substantially equal to the density of the predetermined reference data.

[0036]

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

(First Embodiment) FIG. 1 is a block diagram showing the configuration of a main part of a facsimile apparatus which is an example of an image processing apparatus according to the present invention. Reference numeral 101 denotes a contact sensor unit (for reading an original). CS), and 8dot /
mm × 8.85 line / mm resolution, 8 dot / m
m × 7.7 line / mm resolution or 8 dot / m
It is a CS for a facsimile that reads a brightness value with a resolution of m × 15.4 line / mm. The CS 101 reads a document with a plurality of light receiving elements provided at a pitch of 8 dot / mm in the main scanning direction, and reads the document in any of the above three types in the sub-scanning direction depending on the document conveyance pitch.

Reference numeral 102 denotes an analog image processing unit for performing analog image processing such as direct current reproduction and shading correction on the analog output of the CS 101. Reference numeral 103 denotes a multi-value (for example, 64 levels) digital output of the analog image processing unit 102 for each pixel. A / D converted to data (6 bits)
It is a conversion unit.

Reference numeral 104 denotes a brightness-density conversion table unit for converting the brightness data of each pixel output from the A / D conversion unit 103 into desired density data. Reference numeral 105 denotes a resolution conversion unit A for converting the multi-valued image data converted by the brightness-density conversion table unit 104 into a desired resolution.
Therefore, resolution conversion can be performed by thinning out or interpolating one-pixel multivalued image data. Reference numeral 106 denotes a brightness-density conversion table unit 104 or a resolution conversion unit A.
This is an error diffusion processing unit that performs halftone processing by the error diffusion method on the output data of 105 based on a matrix as shown in FIG. 7 to generate binarized image data.

Reference numeral 107 denotes a data control unit for controlling the transfer of image data according to each mode of transmission, reception and copying.
Reference numeral 08 denotes a resolution conversion unit B for converting the resolution of the binary image data into a desired resolution, and the resolution can be converted by thinning out or interpolating the binary image data of one pixel. Reference numeral 109 is a density correction unit for performing density correction by reversing black pixels on the image data whose resolution has been converted by the resolution conversion unit B108, and 110 is an inkjet printer for performing high-resolution print recording, with a resolution of 360 dpi in this embodiment. I am using a printer.

Reference numeral 111 is a modem for modulating / demodulating image data at the time of transmission / reception, 112 is an NCU for controlling the station line at the time of transmission / reception, and 113 is a C for controlling the above-mentioned respective parts.
It is PU.

When 114 is connected to the 114a side, the resolution is converted by the resolution conversion unit A105, and when connected to the 114b side, data is sent to the error diffusion processing unit 106 without resolution conversion. When the device 115 is the device A and the 115 is connected to the 115a side, the resolution is converted by the resolution converter B108,
When connected to the side, the resolution is converted, such as sending data to the inkjet printer 110 without converting the resolution.
This is the switching device B for selecting not to perform.

Here, since a resolution conversion section for performing resolution conversion of binary data at the time of reception and a resolution conversion section for performing resolution conversion of multi-valued data at the time of copying are separately provided, efficiency can be improved with a simple configuration such as switching the switching device. It is possible to perform each processing well, and it is also possible to perform resolution conversion suitable for each processing.

Next, the flow of image data will be described.

First, in the transmission mode, the transmission original is selected by the operator by the CS 101, for example, 8 dot / mm ×
It is read at a resolution of 7.7 line / mm, this output is corrected by the analog image processing unit 102, and converted into multi-valued digital pixel data per pixel by the A / D conversion unit 103.

This data is stored in the luminance-density conversion table section 1
It is converted into density data at 04, and is switched by the switching unit A114 to 1
14b side, the error diffusion processing unit 106 performs image processing to output binarized image data, and the transmission image data obtained here is 8 dot / m in the apparatus of the present embodiment.
m × 7.7 line / mm.

This image data is sent to the modem 111 by the data processing unit 107, modulated into an analog transmission signal, and sent to the local line through the NCU 112.

Next, in the reception mode, the analog transmission signal coming from the station line is sent to the modem 111 via the NCU 112 and demodulated into digital image data. This resolution is in accordance with the G3 standard, for example, 8 dot / mm × 7.7
line / mm.

The data control unit 107 connects this image data to the 115b side by the switching unit B115, transfers it to the resolution conversion unit B108, and converts the resolution of the one-pixel binary image data by a predetermined method.

That is, 8 dots / mm × 7.7 lin
In order to record e / mm data with the inkjet printer 110 of 360 dpi × 360 dpi, the number of pixels is increased by about 1.77 times in the main scanning direction and 1.84 times in the sub scanning direction. Will be added.

Next, the density correction unit 109 uses the pattern of the image data in order to prevent the image density of the entire image when printed by the ink jet printer 110 from being visually increased due to the increase in the number of pixels due to the above-mentioned resolution conversion. Then, the black pixel is replaced with the white pixel, and the density is corrected.

This data is stored in the inkjet printer 11
0 and the image is recorded with a resolution of 360 dpi × 360 dpi.

Next, in the copy mode, CS101, for example, 8
The original image is read at dot / mm × 15.4 line / mm, and multivalued image data per pixel converted into density data by the brightness-density conversion unit 104 is obtained.

This image data has a resolution conversion unit A10 by connecting the switching unit A114 to the 114a side.
5, the resolution of the image data is converted so that the recording resolution of the inkjet printer 110 (360 dpi × 360 dpi) is obtained. Then, the error diffusion processing unit 106
Then, halftone processing is performed to output binarized image data. The image data obtained here is 360 dpi × 3.
It is binary image data of 60 dpi. Here, since the resolution conversion unit A105 performs resolution conversion according to the recording resolution and the error diffusion processing unit 106 performs binarization by the error diffusion method, it is suitable for the printer without destroying the smooth image processing pattern by the error diffusion process. The obtained image data can be obtained.

This image data is recorded and output by the ink jet printer 110 by connecting the switching unit B115 from the data control unit 107 to the 115b side.

Next, the principle of resolution conversion will be described.

A facsimile apparatus having a printer having a recording density different from that of reading and recording or having a recording density different from the resolution of facsimile communication needs a resolution conversion circuit because recording at the same size as the original is required at the time of reception or copying. Become. For example, 8 dot / mm × 7.7 line / mm
Image data read at a resolution of 360 dpi x 36
When recording with a printer head of 0 dpi, if one pixel corresponds to one pixel for reading and is recorded, the main scanning direction is {8 (dot / mm)} / {360 (dpi
i)} = 0.564 Sub-scanning direction {7.7 (line / mm)} / {360
An image is recorded at a reduction ratio of (dpi) = 0.543. Therefore, if the original data 9 bits are expanded to 16 bits in the main scanning direction and 6 bits to 11 bits in the sub scanning direction, 0.564 x (16/9) = 1.003 sub scanning direction 0.543 x (11 / 6) = 0.996, which means that recording can be performed at about the same size.

FIG. 2 illustrates the principle of the resolution conversion described above. (A) shows the resolution conversion in the main scanning direction, and (b) shows the resolution conversion in the sub-scanning direction. Here, 2a indicates resolution conversion in the main scanning direction, and the read pixel 21a is set to 21 for two recording pixels.
By replacing a 'with 23a' and 23a 'for one recording pixel, it is possible to perform equal-magnification recording in the main scanning direction. Reference numeral 2b indicates resolution conversion in the sub-scanning direction, where one line 21b of read pixels corresponds to 21 lines of two lines of recorded pixels.
b ', and 23b for one recording pixel line like 23b
By substituting b ', it becomes possible to perform equal-magnification recording in the sub-scanning direction. 8dot / mm × 15.4 other than the above example
Image data read with line / mm resolution is 36
When converting to 0 dpi × 360 dpi, the main scanning direction is {8 (dot / mm)} / {360 (dp
i)} = 0.564 Sub-scanning direction {15.4 (line / mm)} / {360
An image is recorded at a magnification of (dpi)} = 1.087. Therefore, in the main scanning direction, conversion is performed in the same manner as described above, and in the sub scanning direction, 25b
It is expanded to 23 bits, and the main scanning direction is 0.564 × (16/9) = 1.003 and the sub scanning direction is 1.087 × (23/25) = 1.000, and it is possible to record at almost the same size. . This operation is performed by the resolution conversion unit A105 in FIG. 1 or the resolution conversion unit B108 in FIG.

In addition to the above, this device has a size of 32% for 90% reduction.
It also has the operation of converting the resolution to 4 dpi. Such resolution conversion is determined by operating the switching unit A114 of FIG. 1 and the switching unit B115 of FIG. 1 by the resolution converting unit A105 of FIG. 1 or the resolution converting unit B108 of FIG. The CPU 113 of FIG. 1 controls the operations of the switching unit A 114 and the switching unit B 115 of FIG. The control of the switching unit is determined by the state, and at the time of transmission, the switching unit A114 of FIG. 1 is connected to the 114b side and the error diffusion processing unit 106 of FIG. When receiving,
1 is connected to the 115a side and is placed in the resolution conversion section B108 of FIG. 1 to convert the resolution of binary image data. When copying, the switching section A114 of FIG. 1 is connected to the 114a side. 1 to convert the resolution of the multi-valued image data, connect the switching unit B115 of FIG. 1 to the 115b side, and bring the inkjet printer 110 of FIG.

Thus, even if the resolution is finally the same, the resolution conversion unit B108 of FIG. 1 performs resolution conversion at the time of reception, and the resolution conversion unit A105 of FIG. 1 at the time of copying.
Resolution conversion is performed with. The resolution conversion performed by the resolution conversion unit A105 and the resolution conversion performed by the resolution conversion unit B108 is 1
The resolution is converted by the same method such as thinning out or interpolating the pixel data, but due to the difference in the processing in the middle, that is, the processing before the resolution conversion, the print density of The OD value is different. Also,
Even when the resolution at the time of reading and the resolution at the time of receiving are different, the OD value is different due to the process of resolution conversion. Therefore, in the present embodiment, the recording density at the time of reception is used as a reference, and in order to match the recording density at the time of copying, the brightness-density conversion table 104 of FIG. It corresponds by. That is, when transmitting, the resolution in the main scanning direction of the receiver is assumed to be 8 dots / mm, and a luminance-density conversion table suitable for that resolution is provided. When copying, the recording resolution in the main scanning direction is 360 dpi. A new brightness-density conversion table is provided.

FIG. 3 shows a case where data of, for example, 64 gradations obtained by reading a predetermined pattern of a halftone image is recorded as in the conventional example up to now and when it is recorded as in this embodiment. Is an OD value when the print density of is measured.
The printing method used so far (the method of performing resolution conversion after performing error diffusion processing, hereinafter referred to as printing method A) and the newly implemented printing method (method of performing resolution conversion before performing error diffusion processing, , Which is referred to as a printing method B), different densities cause printing with different densities even with the same gradation. Therefore, in the case of the same pattern, the luminance-density conversion table unit 1 of FIG.
This can be done by providing a luminance-density conversion table for each reading resolution at 04. FIG. 4 shows a luminance-density conversion table A and a luminance-density conversion table B for printing the same pattern with the same density.

Here, how to determine the brightness-density conversion table will be described. First, the basic luminance-density conversion table A having a predetermined reading resolution is determined. Here, the printing method A is used as a reference. Then, paying attention to FIG. 3, the gradation is x = 5.
When the printing method A is 0, the OD value is 1.0, and in the printing method B, the OD value is 1.13. In the printing method B, the OD value is 1.0 when the gradation is y = 40. Luminance-density conversion table A in FIG.
At the set density corresponding to the gradation x = 50, the brightness is z = 10.
Is. Gradation y corresponding to the set density when the brightness z = 10
= 40 replaces the brightness-density conversion table B. So do this for all gray levels 0-63. Then, the same pattern can be printed with the same density.
A table for printing the same pattern with the same density can be created by performing this processing for all gradations.

With the apparatus of this embodiment, 90% reduction copying can be performed. That is, the read image data is
If the resolution is converted to 24 dpi and this is recorded by a 30 dpi printer, it is possible to print with a recording width of 324/360 = 90%. At this time, since the recording resolution becomes 324 dpi, the density characteristic is different from that at 360 dpi. Therefore, a method similar to the operation of determining the table B described above is performed for 324 dpi to determine the luminance-density conversion table C.

In the case of recording resolutions other than this as well, a reference table A for each resolution used and a luminance-density conversion table in which the densities of the entire image are the same are prepared.

As described above, a brightness-density conversion table is provided for all recording resolutions, and a brightness-density conversion table suitable for the type of reading resolution and recording resolution is selected. By doing so, it is possible to print with the same density when viewing the entire image regardless of which of the recording resolutions it has, and moreover, simply by referring to the contents of the table, it is possible to obtain the desired brightness data at high speed. It can be converted into concentration data.

As described above, according to the present embodiment, when images of the same pattern are input and recorded, the images as a whole can be viewed regardless of the resolution of the input images or the difference in the recording resolution. It is possible to print at the same density. Further, since the tables are created based on the print densities of the images of the predetermined patterns, it is possible to print with the same density even when the processes such as copying and recording of received data are different. Further, at the time of copying, since the resolution conversion matching the recording resolution is performed before the halftone processing such as the error diffusion processing is performed, it is possible to prevent the pattern due to the halftone processing from being destroyed.

(Second Embodiment) In the above-mentioned first embodiment, an example in which the image density is controlled when the ink jet printer 110 which records an image at 360 dpi × 360 dpi is used is shown. In the second embodiment described below, the ink jet printer 110 is made detachable so as to support recording with a plurality of types of pixel densities. That is, the size of one pixel is changed by thinning the ink nozzle, and the ink bleeding method is also different. In addition, the density of the entire image is different due to the overlapping relationship between the recorded pixels due to the different pixel densities. That is, the density of the entire image differs depending on the size of the overlapping portion of the ink. The image density is controlled to eliminate these effects.

The process flow in this case will be described below with reference to FIG.

Here, the case of copy processing will be described. First, in 501, the document image is read by the CS 101. Here, a predetermined resolution (for example, 8 dot /
mm × 15.4 line / mm), or may be read at a resolution selected by the operator.

Next, at 502, the pixel density of the ink jet printer 110 is determined. Here, it is assumed that the inkjet printer 110 is detachable and that the pixel density can be determined by mounting the inkjet printer 110 on the mounting portion. Here, it is assumed that the inkjet printer is, for example, 720 dpi × 720 dpi.

Next, at 503, the luminance according to the resolution at the time of reading and the resolution at the time of recording (here, it is assumed to be the same size)-
Select the density conversion table. Here, as described above, a table is created in advance for each reading resolution based on the printing method A (again, the printing density when printing is performed at 360 dpi × 60 dpi).

Subsequently, at 504, the luminance selected at 503-
The brightness data read by the CS 101 is converted into desired density data based on the density conversion table. The data obtained here is multi-valued image data per pixel.

Next, at 505, resolution conversion is performed by the resolution conversion unit A105 according to the recording resolution of the ink jet printer 110. For example, 8 dot / mm × 15.
If read at 4 line / mm, this is 720d
Convert to pi × 720 dpi.

Next, at 506, the error diffusion processing unit 106 performs halftone processing on the one-pixel multivalued image data and outputs the binarized image data.

Subsequently, at 507, the binarized image data is processed by the ink jet printer 110 at 720 dp.
Record and output at a resolution of i × 720 dpi.

As described above, according to the second embodiment, the brightness-density conversion table is created in consideration of the degree of ink overlap due to the difference in pixel density (pixel-to-pixel spacing), and 360 dpi × 360 dpi. Since the print density in the case of printing is used as a reference, the density of the entire image can be made equal regardless of the difference in pixel density.

In the above embodiment, the error diffusion method is used as the halftone processing, but the halftone processing is not limited to this, and the halftone processing can be artificially performed by the density-preserving image processing pattern as in the error diffusion method. It goes without saying that the method can be applied to the average concentration preservation method and the like.

[0078]

As described above, according to the present invention, an output image having an appropriate density can be obtained regardless of the resolution at the time of outputting.

Further, according to the present invention, it is possible to prevent deterioration of image quality due to resolution conversion.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a facsimile apparatus according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram of resolution conversion in a main scanning direction and a sub scanning direction.

FIG. 3 is a graph showing a difference in print density due to a difference in processing method.

FIG. 4 is a diagram showing an example of a luminance-density conversion table.

FIG. 5 is a diagram showing a flow of processing in the second embodiment.

FIG. 6 is a diagram illustrating a conventional facsimile apparatus.

FIG. 7 is a diagram showing an example of a matrix used in the error diffusion method.

[Explanation of symbols]

 Reference Signs List 101 contact sensor unit 102 analog image processing unit 103 A / D conversion unit 104 brightness-density conversion table unit 105 resolution conversion unit A 106 error diffusion processing unit 107 data processing unit 108 resolution conversion unit B 109 density correction unit 110 inkjet printer 111 modem 112 NCU 113 CPU 114 Switching unit A 115 Switching unit B

Claims (10)

[Claims] 1. An input device for inputting image data, a data conversion device for converting density characteristics of the image data input by the input device, and an output device for outputting the image data at a predetermined resolution. An image processing apparatus, wherein the data converting means converts the density characteristic so that the density becomes substantially the same even if the resolution of the image data output by the output means is different. 2. The data conversion means converts the density characteristic of the image data input by the input means based on a conversion table created for each resolution of the image data output by the output means. 1. The image processing device according to 1. 3. The image processing apparatus according to claim 1, wherein the output unit prints out by an inkjet printer. 4. A resolution conversion means for converting the resolution of the image data input by the input means, wherein the output means is higher than the resolution input by the input means by performing the conversion by the resolution conversion means. The image processing apparatus according to any one of claims 1 to 3, wherein the image data is output at a resolution. 5. Input means for inputting image data, data conversion means for converting density characteristics of the image data input by the input means, and resolution of the image data converted by the data conversion means to a predetermined resolution. Resolution conversion means for converting; halftone processing means for performing halftone processing on the image data converted by the resolution conversion means; and output for outputting the image data halftone processed by the halftone processing means at the predetermined resolution. An image processing apparatus comprising: a means for converting the density characteristics so that the density of the image data input by the input means is substantially equal to the density of predetermined reference data. 6. The image processing apparatus according to claim 5, wherein the halftone processing means is a binarization processing by a density preservation method. 7. The image processing apparatus according to claim 5, wherein the output unit prints out by an inkjet printer. 8. The output device outputs the image data at a resolution higher than the resolution input by the input device by performing conversion by the resolution conversion device. The image processing device according to. 9. An input step of inputting image data, a data conversion step of converting density characteristics of the input image data, and an output step of outputting image data at a predetermined resolution, the data conversion step. Then, the image processing method is characterized in that the density characteristics are converted so that the densities are substantially the same even if the resolutions of the image data output in the output step are different. 10. An input step of inputting image data, a data converting step of converting density characteristics of the input image data, and a resolution of converting the resolution of the image data converted in the data converting step to a predetermined resolution. A conversion step, a halftone processing step of performing a halftone process on the image data converted in the resolution conversion step, and an output step of outputting the image data subjected to the halftone processing in the halftone processing step at the predetermined resolution. An image processing method, wherein in the data conversion step, the density characteristic is converted so that the density of the image data input in the input step is substantially equal to the density of predetermined reference data.