JP4974072B2 - Image processing device - Google Patents

Description

  The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus such as a digital copier or a digital multi-function peripheral (MFP machine) that combines functions of a copier, a facsimile, a printer, a scanner, and the like.

  2. Description of the Related Art Conventional image processing apparatuses such as a digital copying machine and a digital multifunction machine read an original image as a digital color image signal and form an output color image of the original image. A color image can be copied in a short time without degrading the image quality. For this purpose, for example, digital filter processing for reducing image deterioration after image compression is performed on the color image signal, and the image is compressed and stored. The stored color image signal is expanded and digital filter processing for reducing image deterioration is performed to form an output color image. Below are some examples of prior art related to this.

  The “image processing apparatus” disclosed in Patent Document 1 performs a first filter process on an input image signal read by a scanner, compresses and stores (accumulates) image data after the first filter process, and stores The compressed image is expanded to perform the second filter processing. In the first filter processing, high frequency components are dropped in order to suppress image degradation due to compression. In the second filter process, the deterioration of the MTF characteristic (Modulation Transfer Function characteristic: spatial frequency characteristic) at the time of reading by the scanner is corrected, and the high frequency component dropped by the first filter process is emphasized. An image area separation process is performed on the input image, and the filter is switched according to the image characteristics (character / halftone dot / photograph) in both the first filter process and the second filter process.

The “image processing apparatus” disclosed in Patent Document 2 performs suitable image processing according to the attributes of image data to be processed when performing a plurality of image processing on image data. Image data generated by the scanner is supplied to an edge detection unit, and edge information is acquired by the edge detection unit as an attribute signal representing an image attribute. The edge information is supplied to the first correction unit, the second correction unit, and the third correction unit, and is corrected to a signal representing a different attribute in each correction unit, and a filter processing unit, a UCR / black generation unit, The image data is supplied to a part that performs various image processing, such as a γ correction unit and a pseudo halftone unit. Then, image processing corresponding to different attributes of the image supplied from each correction unit is executed in each unit.
JP 2001-309183 A Japanese Unexamined Patent Publication No. 2005-045404

  However, the conventional image processing apparatus has the following problems. In the second filter processing, the high-frequency component dropped in the first filter processing is emphasized, and MTF deterioration in scanner reading is corrected. For this reason, the MTF characteristics of the scanner and the filter characteristics of the first filter processing affect the characteristics of the second filter processing. Therefore, the filter characteristics of the second filter processing must be individually designed according to the MTF characteristics of the scanner and the filter characteristics of the first filter processing, which complicates the design method and is compatible between devices. Also disappear. Further, since both the first filter processing and the second filter processing are controlled by the same image feature (character / halftone dot / photo), the number of types of filters increases, and the circuit scale and the memory amount increase. .

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to request image data processed by the first filter of the image processing apparatus using a second filter that does not depend on the first filter in other image processing apparatuses. It is to be able to convert to an image of image quality. It is another object of the present invention to reduce the circuit size and memory amount of the second filter and to easily output with the image characteristics designated by the user.

In order to solve the above problems, the present invention, an image reading apparatus and an image feature for each pixel of the input image data character or dot or photographic generating input image data by scanning the originals optically And image feature detection means for outputting image feature data representing characters or non-characters and halftone dots or non-halftone dots, and for the input image data for characters or halftone dots based on the respective image feature data Alternatively, a first filter processing unit that performs photographic filter processing to obtain a predefined and unified image quality, and image feature data representing the character or non-character in the image data after the filter processing by the first filter processing unit based on, and a second filter processing means for performing character for filtering or non-character filter process, the configuration Ru comprising a.

Also, reduced by the lossless compression means for compressing the image data after the filtering, a means for storing the compressed image data, the information amount of the image feature data outputted from the image feature detection unit by the first filtering processing means Means and means for storing image feature data with a reduced amount of information. The filter pixel size of the second filter processing means is made smaller than the filter pixel size of the first filter processing means. Comprising means for transmitting the image data and the image feature data after filtering by the first filter processing means to an external device. Comprising means for receiving image data and the image feature data of the unified image quality from the external device. Comprising means for printing the image data after the filtering by the second filter processing unit. A setting unit configured to set a characteristic designated by the user for the output image as an instruction characteristic; and a unit configured to control the filter characteristic of the second filter processing unit based on the set instruction characteristic. The indicating characteristic is a degree of sharpness.

Also, the first filtering means, for suppressing high-frequency components of the high-frequency component suppressing dots filter processing section of the high-frequency emphasizing the character filter unit components and the spatial frequency and the spatial frequency of the spatial frequency A photographic filter processing unit and a selector for selecting an output of each filter processing unit based on the image feature data, and the second filter processing unit includes: a character filter processing unit that emphasizes a high frequency component of the spatial frequency; and a spatial frequency A non-character filter processing unit that suppresses the high-frequency component of the image and a selector that selects an output of each filter processing unit based on the image feature data.

  With the above configuration, the image processing apparatus can convert image data with uniform image quality into a target image for printing or the like with a small second filter that does not depend on the first filter. Furthermore, the image can be converted into an image having a desired image quality with a simple configuration.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to FIGS.

  The first embodiment of the present invention controls the filter characteristics based on a specific type of image feature of the input image, performs the first filter processing on the input image data, and generates image data with uniform image quality. This is a digital image processing apparatus that compresses and saves, decompresses compressed image data, controls filter characteristics based on some image features of a specific type, and performs second filter processing.

  FIG. 1 is an overall configuration diagram of a digital image processing apparatus (MFP machine) in Embodiment 1 of the present invention. The digital image processing apparatus is not limited to an MFP, and may be a single function copying machine. In FIG. 1, a reading device 1 is a device that scans a document and outputs digital image data. The first image data processing device 2 is a device that performs image processing on the digital image data from the reading device 1. The first image data processing device 2 has a first filter processing unit. The bus control device 3 is a device that exchanges various data such as image data and control commands necessary in the digital image processing device. The second image data processing unit 4 is an apparatus that performs image processing on the digital image data processed by the first image data processing apparatus 2. The second image data processing unit 4 includes a second filter processing unit.

  The HDD 5 is a storage device for accumulating digital image data and accompanying information of the digital image data. The CPU 6 is a microprocessor that controls the entire control of the digital image processing apparatus. The memory 7 is a volatile memory used for temporarily storing programs and intermediate processing data when the CPU 6 controls the digital image processing apparatus. The plotter I / F device 8 is a device that sends digital image data from the CPU 6 to the plotter device 9. The plotter device 9 is a device that outputs an image on printing paper by an electrophotographic process or the like.

  The operation display device 10 is a part that performs a user interface with the digital image processing device. The operation display device 10 includes an LCD (liquid crystal display device) and a key switch. It is a device that detects input. The line I / F device 11 is a device that exchanges image data via a telephone line. The external I / F device 12 is a device that inputs and outputs various control signals and image data via a network (LAN). The bridge circuit 13 is a general-purpose circuit of a bridge function of a bus called South Bridge. The ROM 14 is a memory that stores a program used when the CPU controls the digital image processing apparatus. The FAX 15 is a FAX apparatus outside the digital image processing apparatus (MFP machine). The PC 16 is a personal computer outside the digital image processing apparatus (MFP machine).

  FIG. 2 is a block diagram of the first image data processing apparatus. In FIG. 2, an image area separation processing unit 30 is means for determining whether each pixel is a character or a halftone dot and outputting a separation signal. The scanner γ conversion unit 31 is means for performing γ conversion of the read image data. The first filter processing unit 32 is a means for performing filter processing according to whether it is a character, a halftone dot or a photograph. The color conversion unit 33 is means for converting the color space of the image data. The compression processing unit 34 is means for compressing image data. The accumulated separation signal generator 35 is a means for outputting only the information of “character / non-character” and “chromatic / achromatic” in the separation signal. The compression processing unit 36 is means for reversibly compressing the separated signal.

FIG. 3 is a block diagram of the second image data processing device 4 . In FIG. 3, a decompression processing unit 51 is means for performing decompression processing on compressed image data. The decompression processing unit 52 is means for performing decompression processing of the compressed separated signal. The second filter processing unit 53 is means for performing filter processing according to whether or not the character is a character. The color conversion unit 54 is means for converting image data into data in the printer color space. The printer γ conversion unit 55 is means for performing γ conversion on data in the printer color space. The gradation processing unit 56 is a means for performing pseudo halftone processing.

  FIG. 4 is a graph showing the frequency characteristics of each filter of the first filter processing unit. FIG. 5A is a block diagram of the filter processing unit 32. FIG. 5B shows character filter coefficients. FIG. 5C shows halftone filter coefficients. FIG. 5D shows photographic filter coefficients. FIG. 6 is a graph showing the frequency characteristics of each filter of the second filter processing unit. FIG. 7A is a block diagram of the second filter processing unit 53. FIG. 7B shows character filter coefficients. FIG. 7C shows non-character filter coefficients.

  The function and operation of the digital image processing apparatus according to the first embodiment of the present invention configured as described above will be described. First, an outline of functions of the digital image processing apparatus will be described with reference to FIG. The reading device 1 scans the original to obtain the density information of the original, and obtains RGB 8-bit digital image data. The first image data processing device 2 performs image processing such as filter processing and compression processing on the image data input from the reading device 1. That is, the image feature detection unit of the first image data processing device 2 detects the image feature of each pixel of the input image data to obtain image feature data. Based on the specific type of image feature, the filter characteristic of the first filter processing means of the first image data processing device 2 is controlled to perform the first filter processing on the input image data. In the first filter processing means, for example, the filter characteristics are controlled based on the image characteristics of “character / non-character” and “halftone / non-halftone”. The image data after the first filter processing is compressed, the image feature data is also compressed, transferred to the HDD 5 via the bus control device 3 under the control of the CPU 6, and stored. If necessary, the image data and the image feature data are transmitted to the PC 16 or the like outside the device via the external I / F device 12 and the network (LAN).

  Under the control of the CPU 6, the compressed image data and image feature data are extracted from the HDD 5 via the bus control device 3. Image data and image feature data can also be received from a PC 16 or the like outside the apparatus. The second image data processing unit 4 performs image processing such as decompression processing and filter processing on the compressed image data. That is, the second filter process is performed on the decompressed image data by the second filter processing unit of the second image data processing unit 4. At this time, the filter characteristic is controlled based on some image features of the specific types of image features, for example, “character / non-character” image features. Necessary image processing such as color conversion is performed on the image data subjected to the second filter processing to obtain CMYK digital image data, which is sent to the plotter device 9 via the plotter I / F device 8. The plotter I / F device 8 receives the CMYK digital image data sent from the CPU 6 and outputs it to the dedicated I / F of the plotter device 9. When the plotter device 9 receives the CMYK digital image data, the plotter device 9 outputs an image on a printing paper by an electrophotographic process using a laser beam. Similarly, image data for FAX transmission can be created. The image processing method can be processed by software by an image processing program describing a processing procedure for executing the image processing method by a computer.

  Next, the operation and role of the first image data processing apparatus will be described with reference to FIG. The role of the first filter processing unit 32 in the first image data processing device is to create image data to be stored in the HDD in the MFP. The stored image data has a unified image quality independent of the MFP model. Here, “image quality” means the resolution of the character part, the smoothness of the halftone dots of the printed document, and the like. This is because image quality is guaranteed when image data is exchanged with other types of MFPs. How to define this image quality is determined by the design guidelines, but the character portion emphasizes the resolution, and for the halftone dot of the printed document, the high-line number halftone dot is smoothed so that the character portion The image quality of the pattern part can be made compatible. In addition, the photographic part also smoothes high-frequency components in order to remove noise.

  The first image data processing device 2 receives RGB format image data from the reading device 1. The image area separation processing unit 30 determines “character / non-character”, “halftone dot / non-halftone dot”, and “chromatic / achromatic” for each pixel from the characteristics of the image input from the reading device 1, and the separation signal Output as. Since the image area separation process may use a known technique, a detailed description thereof is omitted. The scanner γ conversion unit 31 performs γ conversion on the read image data of 8 bits for each RGB, and converts the read image data so as to have, for example, lightness linear characteristics. The first filter processing unit 32 performs the first filter processing based on the information of “character / non-character” and “halftone / non-halftone” in the separated signal.

  The color conversion unit 33 converts the image data after the first filter processing into RGB data in a color space having a certain characteristic. This color space is, for example, an Adobe-RGB space defined by Adobe. The compression processing unit 34 compresses RGB data. The compression method used here is a lossy compression method such as JPEG compression. The accumulated separation signal generation unit 35 removes only the information of “character / non-character” and “chromatic / achromatic” from the separation signal generated by the image area separation processing unit 30 except for the information of “halftone / non-halftone”. Is output. The compression processing unit 36 compresses the separated signal. The compression method used here must be a lossless compression method. The RGB image data and the separation signal generated by the image data processing device 1 are stored in the HDD.

  Next, the operation and role of the second image data processing apparatus will be described with reference to FIG. The role of the second filter processing unit 53 in the second image data processing device is to obtain the optimum image quality when outputting the image data stored in the HDD to the plotter device. For this purpose, it is necessary to design the filter coefficient in consideration of the characteristics of the plotter device.

  The decompression processing unit 51 performs decompression processing on the compressed RGB image data generated by the image data processing apparatus 1. The decompression processing unit 52 performs decompression processing on the post-compression separated signal generated by the image data processing apparatus 1 to generate “character / non-character” and “chromatic / achromatic” separation signals. The second filter processing unit 53 performs the second filter processing based on the “character / non-character” information. The color conversion unit 54 converts RGB 8-bit data into 8-bit CMYK, which is the color space of the plotter device. At this time, color conversion is performed so that only the K signal is output from the “character / non-character” and “chromatic / achromatic” information to the “character” and “achromatic” areas. This is to suppress the coloring of the black character portion of the image.

  The printer γ conversion unit 55 performs γ conversion on the CMYK data in order to correct the gradation characteristics of the plotter device. The gradation processing unit 56 performs pseudo halftone processing such as dither processing and error diffusion processing in order to convert 8-bit data of CMYK into the number of gradations of the plotter device (for example, 2 bits of CMYK). The CMYK data generated by the image data processing device 2 is output as an image on printing paper by the plotter device.

  Next, the frequency characteristics of each filter of the first filter processing unit will be described with reference to FIG. The character filter is a filter that emphasizes up to high frequency components. The halftone dot filter is a filter used for a general printed document, and is a filter in which 175 line / inch is smoothed and low frequency components are emphasized. The photographic filter is also a filter in which high frequency components around 300 lines / inch are smoothed and low frequency components are emphasized. By switching such a filtering process according to a separation signal indicating an image feature, optimum accumulated image data is generated.

Next, the first filter processing unit will be described with reference to FIG. In the selector, the following selection is performed based on the separation signal indicating the image feature.
(1) When the separation signal indicating the image feature is “character”, the character filter processing is performed.
(2) When the separation signal indicating the image feature is “non-character” and “halftone”, the halftone filter processing is performed.
(3) When the separation signal indicating the image feature is “non-character” and “non-halftone”, a photographic filter process is performed.

  FIG. 5B shows an example of filter coefficients used for character filter processing. FIG. 5C shows an example of filter coefficients used for the halftone dot filter processing. FIG. 5D shows an example of filter coefficients used for the photographic filter processing. In this example, the method of selecting the output of a plurality of filters is shown as a method of controlling the filter characteristics. However, the filter characteristics may be controlled by other known methods such as a method of switching filter coefficients.

  Next, the frequency characteristics of each filter of the second filter processing unit will be described with reference to FIG. The character filter is a filter that emphasizes even high-frequency components in order to obtain a sharp image when output by a plotter device. The non-character filter is a filter that slightly emphasizes only the low frequency component. Since the halftone dots and the like of the printed document are smoothed by the first filter processing unit, it is not necessary to perform strong smoothing by the second filter processing unit. Therefore, the filter size of the second filter processing unit can be made smaller than the filter size of the first filter processing unit. Of course, since these filters depend on the characteristics of the plotter device, they may be completely different filters.

Next, the second filter processing unit will be described with reference to FIG. In the selector, the following selection is performed based on the separation signal indicating the image feature.
(1) When the separation signal indicating the image feature is “character”, the character filter processing is performed.
(2) When the separation signal indicating the image feature is “non-character”, non-character filter processing is performed.

  FIG. 7B shows an example of filter coefficients used for character filter processing. FIG. 7C shows an example of filter coefficients used for the non-character filter processing. In this example, the method of selecting the output of a plurality of filters is shown as a method of controlling the filter characteristics. However, the filter characteristics may be controlled by other known methods such as a method of switching filter coefficients.

With the above configuration, the roles of the two filters are shared as follows.
(1) The first filter (the first filter processing unit 32 in the first image data processing apparatus) performs processing for generating accumulated image data with a unified image quality.
(2) The second filter (second filter processing unit 53 in the second image data processing device) performs processing for outputting the accumulated image data by the plotter device.
Furthermore, since the stored image data has a unified image quality, the second filter can be designed independently without depending on the design of the first filter.

  Further, since the second filter has a smaller number of switching by the separation signal than the first filter, the circuit scale can be made smaller than when the first filter and the second filter are switched by the same separation signal. Furthermore, in order to smooth halftone dots, a filter having a certain size is required. However, since the role of smoothing halftone dots is only the first filter, the second filter is smaller than that. A size filter is sufficient. As shown in FIG. 5, the first filter has a size of 7 × 7 pixels, and the second filter has a size of 5 × 5 pixels as shown in FIG. Thus, by reducing the size of the second filter, the circuit scale and the amount of memory can be suppressed.

  In the first embodiment, an example in which a fixed coefficient filter is switched by a separation signal indicating an image feature has been described. However, in a halftone dot portion or a photographic portion, an edge amount of an image is extracted and filter characteristics are controlled based on the edge amount. It is also possible to perform adaptive filter processing. In the image area separation processing, “character / non-character”, “halftone / non-halftone”, and “chromatic / achromatic” are determined. It is also possible to determine “/ low line number halftone dot” and divide the halftone dot filter process into a high line number halftone dot filter process and a low line number halftone dot filter process in the first filter process. As a result, processing corresponding to the number of halftone dots of the printed document can be performed, and a higher quality image can be generated.

  As described above, in the first embodiment of the present invention, the digital image processing apparatus controls the filter characteristics based on a specific type of image feature of the input image, performs the first filter processing on the input image data, and compresses it. Since the compressed image data is decompressed and the second filter processing is performed by controlling the filter characteristics based on some image features of the specific type, the two filters are independent. Can be designed.

  Embodiment 2 of the present invention is an image processing apparatus that allows a user to set the sharpness degree of an output image and controls the characteristics of the second filter based on the set sharpness degree.

  The basic configuration of the image processing apparatus according to the second embodiment of the present invention is the same as that according to the first embodiment. The part relating to the sharpness setting is different from the first embodiment. FIG. 8 is a graph showing an example of filter characteristics for each sharpness setting value of the character filter used in the image processing apparatus according to the second embodiment of the present invention.

  Setting means for allowing the user to set the degree of sharpness of the output image is provided. The user can make settings related to the image quality of the output image on the operation display device. The characteristics of the second filter are controlled based on the set sharpness degree. An operation when there is a sharpness setting in the setting relating to image quality will be described. The image quality other than sharpness can be controlled similarly. The sharpness is set to 5 levels (setting values 1 to 5), where the setting value 5 is the highest sharpness and the setting value 1 is the lowest sharpness. The set value of the sharpness setting is reflected in the characteristics of the second filter. Specifically, the filter coefficients of the character filter and the non-character filter shown in FIG. 6 are switched based on the set value of the sharpness setting.

  With reference to FIG. 8, the filter characteristics for the setting values of the sharpness settings of the character filter will be described. When the setting value of the sharpness setting is 5, the emphasis is strongest, and when the setting value is 1, the emphasis is weakest (smoothed). Similarly, the non-character filter has a filter characteristic that gives the strongest enhancement when the setting value of the sharpness setting is 5 and the weakest enhancement characteristic when the setting value is 1. Filter coefficients that realize such characteristics are prepared for characters and non-characters. At the time of printing, a filter coefficient corresponding to the set value of the sharpness setting is used. The characteristics of the first filter do not depend on the sharpness setting. Therefore, the image data stored in the HDD in the MFP also does not depend on the sharpness setting. Therefore, when re-outputting the image data stored in the HDD, the sharpness setting can be changed and output.

  With the above configuration, it is possible to easily cope with the sharpness setting set by the user. Further, since the first filter does not cope with the sharpness setting, the design man-hour is reduced, and the circuit scale and the memory amount can be suppressed.

  As described above, in the second embodiment of the present invention, the image processing apparatus is configured to allow the user to set the sharpness degree of the output image and control the characteristics of the second filter based on the set sharpness degree. An image having the image quality desired by the user can be output with a simple configuration.

  The image processing apparatus of the present invention is most suitable as a digital copying machine or a digital multifunction peripheral (MFP machine) that compresses and stores image data and decompresses and prints the compressed image data.

1 is an overall configuration diagram of a digital image processing apparatus (MFP machine) in Embodiment 1 of the present invention. It is a block diagram of the 1st image data processing apparatus of the digital image processing apparatus (MFP machine) in Example 1 of this invention. It is a block diagram of the 2nd image data processing apparatus of the digital image processing apparatus (MFP machine) in Example 1 of this invention. It is a graph which shows the frequency characteristic of each filter of the 1st filter process part of the digital image processing apparatus (MFP machine) in Example 1 of this invention. FIG. 3 is a block diagram of a first filter processing unit of the digital image processing apparatus (MFP machine) in Embodiment 1 of the present invention and examples of filter coefficients used for character, halftone, and photo filter processing. It is a graph which shows the frequency characteristic of each filter of the 2nd filter process part of the digital image processing apparatus (MFP machine) in Example 1 of this invention. 2 is a block diagram of a second filter processing unit of the digital image processing apparatus (MFP machine) in Embodiment 1 of the present invention and examples of filter coefficients used for character and non-character filter processing. FIG. It is a graph which shows the example of the filter characteristic with respect to the setting value of each sharpness setting of the filter for characters used with the digital image processing apparatus (MFP machine) in Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reading apparatus, 2 ... 1st image data processing apparatus, 3 ... Bus control apparatus, 4 ... 2nd image data processing apparatus, 5 ... HDD, 6 ... CPU, 7 ... Memory, 8 ... Plotter I / F device, 9 ... Plotter device, 10 ... Operation display device, 11 ... Line I / F device, 12 ... External I / F device, 13 ... Bridge circuit, 14 ... ROM, 15 ... FAX, 16 ... PC, 30 ... Image area separation processing unit, 31 ... Scanner gamma conversion unit, 32 ... First Filter processing unit, 33 ... color conversion unit, 34 ... compression processing unit, 35 ... accumulation separation signal generation unit, 36 ... compression processing unit, 51 ... decompression processing unit, 52 ... Decompression processing unit, 53 ... second filter processing unit, 54 ... color conversion unit, 55 ... printer γ conversion unit, 56 ... gradation processing unit.

Claims (15)

An image reading device that optically scans a document to generate input image data;
Image feature detection means for detecting a character or halftone dot or photograph as an image feature for each pixel of the input image data and outputting image feature data representing the character or non-character and halftone dot or non-halftone dot ;
First filter processing means for obtaining a predetermined and unified image quality by applying character, halftone, or photo filter processing to the input image data based on each image feature data ;
Second filter processing means for applying character filter processing or non-character filter processing to the image data after the filter processing by the first filter processing means, based on image feature data representing the characters or non-characters ;
The image processing apparatus according to claim Rukoto equipped with. Means for compressing the image data after filtering by the first filter processing means, means for storing the compressed image data, means of reducing in lossless compression of information amount of the image feature data outputted from the image feature detection unit The image processing apparatus according to claim 1, further comprising: means for storing image feature data with a reduced amount of information.   2. The image processing apparatus according to claim 1, wherein a filter pixel size of the second filter processing unit is smaller than a filter pixel size of the first filter processing unit. The image processing apparatus according to claim 1, characterized in that it comprises means for transmitting the image data and the image feature data after filtering by the first filter processing means to an external device. The image processing apparatus according to claim 1, characterized in that it comprises means for receiving image data and the image feature data of the unified image quality from the external device. The image processing apparatus according to claim 1, characterized in that it comprises means for printing the image data after the filtering by the second filter processing unit.   2. The apparatus according to claim 1, further comprising: setting means for setting a characteristic designated by the user for the output image as an instruction characteristic; and means for controlling the filter characteristic of the second filter processing means based on the set instruction characteristic. The image processing apparatus described.   The image processing apparatus according to claim 7, wherein the instruction characteristic is a degree of sharpness. The first filter processing means includes: a character filter processing unit that emphasizes a high frequency component of a spatial frequency; a halftone dot filter processing unit that suppresses a high frequency component of a spatial frequency; and a photo filter that suppresses a high frequency component of a spatial frequency. A filter processing unit and a selector for selecting an output of each filter processing unit based on the image feature data, and the second filter processing means includes a character filter processing unit for emphasizing a high frequency component of the spatial frequency and a spatial frequency The image processing apparatus according to claim 8, further comprising: a non-character filter processing unit that suppresses a high frequency component; and a selector that selects an output of each filter processing unit based on the image feature data . An image processing method in an image reading apparatus for optically scanning a document to generate input image data,
An image feature detection step of detecting a character or halftone dot or photograph as an image feature for each pixel of the input image data and outputting image feature data representing the character or non-character and halftone dot or non-halftone dot;
A first filter processing step of obtaining character quality, a halftone dot or a photographic filter processing on the input image data based on each image feature data to obtain a predefined and unified image quality;
A second filter processing step of applying character filter processing or non-character filter processing to the image data after the filter processing by the first filter processing step, based on image feature data representing the characters or non-characters;
Images processing how to said Rukoto to have a. A step of compressing the image data after filtering by the first filter processing step, a step of storing the compressed image data, a step of reversibly compressing the image feature data to reduce the amount of information, and an image having a reduced amount of information The image processing method according to claim 10, further comprising each step of storing feature data . The image processing method according to claim 10, further comprising a step of transmitting the image data and the image feature data after the filter processing in the first filter processing step to an external device . The image processing method according to claim 10, further comprising a step of receiving image data and image feature data with unified image quality from an external device . The image processing method according to claim 10, further comprising a step of controlling filter characteristics in the second filter processing step based on a sharpness degree set by a user . 15. An image processing program that describes a processing procedure for executing each step in the image processing method according to claim 10 by a computer .

Images