JP2002218251A - Image processor, image processing system, image processing method and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processor by which image degradation due to compression is reduced. SOLUTION: An encoding means 104 encodes an object image from an image input means 130, a code amount detection means 107 detects a code amount in the encoding means 104 and the image input means 130 inputs the object image again on the basis of the detected result of the code amount detection means 107. A first spatial frequency correction means 105 corrects spatial frequency characteristics for the object image inputted again by the image input means 130 and the encoding means 104 encodes the object image after the correction by the first spatial frequency correction means 105.

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, an image processing system, an image processing method and an image processing method for use in an apparatus or system for compressing a color image. The present invention relates to a storage medium readable by a computer.

[0002]

2. Description of the Related Art Conventionally, as a compression method of a color still image, a JPEG method using discrete cosine transform, a WPEG
A method using an avelet transform is often used. In this type of compression method, the image deterioration and the compression ratio are determined by making the quantization step coarser or making the quantization step finer.

For example, in a still image to be compressed, the quantization step in a photographic area where image quality degradation is relatively inconspicuous is made coarse, and the quantization step in a character area where image quality degradation is relatively inconspicuous is made fine. Also, by discriminating between the natural image area and the computer graphics area, the quantization step for the natural image area where the image quality deterioration is relatively inconspicuous is coarsened, and the quantization step for the computer graphics area where the image quality deterioration is relatively noticeable is Make it fine.

[0004] If the desired compression ratio is not achieved during image compression, the desired compression ratio is achieved by performing re-compression such as by making the quantization step coarser.

[0005]

However, the conventional image compression method as described above has the following problems. For example, when the compression rate is less than a desired compression rate during image compression, the quantization step is configured to be coarser and compression is performed. Therefore, a quantization table with a higher compression than the first compression is used. In other words, since the quantization table is changed to a high-compression quantization table and high-compression is performed, the character image quality is greatly deteriorated.

Accordingly, the present invention has been made to eliminate the above-mentioned drawbacks, and is capable of reducing image deterioration due to compression, an image processing system, an image processing system, an image processing method, and an image processing method. It is an object of the present invention to provide a storage medium in which processing steps to be performed are stored in a computer-readable manner.

[0007]

For such a purpose,
According to a first aspect of the present invention, there is provided image input means for inputting a target image, coding means for coding the target image input by the image input means, and coding data of the target image obtained by the coding means. Code amount detecting means for detecting the code amount;
For the target image input by the image input means,
An image processing apparatus comprising: a first spatial frequency correction unit that corrects a spatial frequency characteristic, wherein the image input unit inputs a target image again based on a detection result of the code amount detection unit, The first spatial frequency correction means corrects the spatial frequency characteristics of the target image input again by the image input means, and the encoding means corrects the target image after the correction by the first spatial frequency correction means. Is encoded.

[0008] In a second aspect based on the first aspect,
The image input means inputs an attribute flag indicating an attribute of a region in the target image together with the target image, and the first spatial frequency correction means corrects the spatial frequency characteristic based on the attribute flag. It is characterized by the following.

[0009] A third invention is the above-mentioned second invention, wherein:
The first spatial frequency correction means corrects different spatial frequency characteristics for each predetermined region included in the target image based on the attribute flag.

In a fourth aspect based on the first aspect,
Decoding means for decoding the encoded data of the target image obtained by the coding means; and decoding the target image obtained by the decoding means by the first spatial frequency correction means. It is characterized by comprising a first spatial frequency correction means for correcting the corresponding spatial frequency characteristic.

According to a fifth aspect, in the first aspect,
The first spatial frequency correction unit corrects the spatial frequency characteristics within M × N pixels of the target image, and the encoding unit applies the correction to the target image after the correction by the first spatial frequency correction unit. On the other hand, the encoding is performed by selecting a quantization coefficient to be applied within M × N pixels.

In a sixth aspect based on the first aspect,
The encoding means performs encoding according to the JPEG method.

A seventh aspect of the present invention is an image processing system in which a plurality of devices are communicably connected to each other, wherein at least one of the plurality of devices is one of the first to sixth aspects.
And a function of the image processing apparatus according to any one of the above.

An eighth invention is an image processing method for encoding an arbitrary image, comprising: an encoding step of encoding an input target image; and an encoding of the target image obtained by the encoding step. A code amount detecting step of detecting the code amount of the data, and a re-input step of re-inputting the target image based on the detection result in the code amount detecting step,
A spatial frequency correction step of correcting a spatial frequency characteristic of the target image re-input in the re-input step, wherein the encoding step encodes the target image after the correction in the spatial frequency correction step. It is characterized by including the step of performing.

According to a ninth aspect, in the eighth aspect,
The spatial frequency correction step includes a step of correcting the spatial frequency characteristic based on an attribute flag input together with the target image and indicating an attribute of a region in the target image.

According to a tenth aspect, there is provided an image input step of inputting a target image, an encoding step of encoding the target image input in the image input step, and a code of the target image obtained in the encoding step. An image processing method comprising: a decoding step of decoding encoded data; and an image output step of outputting a decoded target image obtained in the decoding step, wherein the target input by the image input step is provided. An image area separating step of determining an attribute of a region included in the image; a code amount detecting step of detecting a code amount of encoded data of the target image obtained in the encoding step; and a detection in the code amount detecting step A code amount determining step of determining whether or not a predetermined code amount has been achieved based on the result, and a code amount determining step based on the determination result in the code amount determining step. And a re-input control step of controlling whether re-input of the target image is performed in the image input step; and performing the encoding in the encoding step by re-input of the target image in the re-input control step. A spatial frequency correction step of correcting different spatial frequency characteristics for each region included in the target image based on the determination result in the separation step.

An eleventh invention is directed to an image input step of inputting a target image, an encoding step of encoding the target image input in the image input step, and a code of the target image obtained in the encoding step. An image processing method comprising: a decoding step of decoding encoded data; and an image output step of outputting a decoded target image obtained in the decoding step, wherein the target input by the image input step is provided. An image area separating step of determining an attribute of a region included in the image; a code amount detecting step of detecting a code amount of encoded data of the target image obtained in the encoding step; and a detection in the code amount detecting step A code amount determining step of determining whether or not a predetermined code amount has been achieved based on the result, and a code amount determining step based on the determination result in the code amount determining step. And a re-input control step of controlling whether re-input of the target image is performed in the image input step; and performing the encoding in the encoding step by re-input of the target image in the re-input control step. A first method of correcting different spatial frequency characteristics for each region included in the target image based on the determination result in the separation step
When performing the encoding in the encoding step by re-inputting the target image in the re-input control step and the spatial frequency correction step, the decoding is performed based on the determination result in the image area separation step. A second spatial frequency correction step of correcting different spatial frequency characteristics for each region included in the obtained decoded target image.

According to a twelfth aspect of the present invention, there is provided an image input step of inputting a target image, an encoding step of encoding the target image input in the image input step, and a code of the target image obtained in the encoding step. An image processing method comprising: a decoding step of decoding encoded data; and an image output step of outputting a decoded target image obtained in the decoding step, wherein the target input by the image input step is provided. An image area separation step of determining an attribute of a region included in the image; an attribute processing step of statistically processing information of the attribute in the image area separation step in a pixel block of a predetermined size set in advance; A selection step of selecting the quantization coefficient in the encoding step in the pixel block of the predetermined size based on a processing result in the attribute processing step; A code amount detecting step for detecting the code amount of the coded data of the target image obtained in the coding step, and whether a predetermined code amount has been achieved by the detection result in the code amount detecting step. A code amount determining step of determining whether or not a target image is re-input in the image input step based on a determination result in the code amount determining step; and a re-input control step. When encoding is performed in the encoding step by re-input of the target image according to the above, based on the determination result in the image area separation step, a spatial frequency for correcting a different spatial frequency characteristic for each region included in the target image And a correcting step.

A thirteenth invention is directed to an image input step of inputting a target image, an encoding step of encoding the target image input in the image input step, and a code of the target image obtained in the encoding step. An image processing method comprising: a decoding step of decoding encoded data; and an image output step of outputting a decoded target image obtained in the decoding step, wherein the target input by the image input step is provided. An image area separation step of determining an attribute of a region included in the image; an attribute processing step of statistically processing information of the attribute in the image area separation step in a pixel block of a predetermined size set in advance; A selection step of selecting the quantization coefficient in the encoding step in the pixel block of the predetermined size based on a processing result in the attribute processing step; A code amount detecting step for detecting the code amount of the coded data of the target image obtained in the coding step, and whether a predetermined code amount has been achieved by the detection result in the code amount detecting step. A code amount determining step of determining whether or not a target image is re-input in the image input step based on a determination result in the code amount determining step; and a re-input control step. In the case where encoding is performed in the encoding step by re-input of the target image according to the above, based on the determination result in the image area separation step, correction of a spatial frequency characteristic different for each region included in the target image is performed.
When performing the encoding in the encoding step by re-inputting the target image in the re-input control step and the spatial frequency correction step, the decoding is performed based on the determination result in the image area separation step. A second spatial frequency correction step of correcting different spatial frequency characteristics for each region included in the obtained decoded target image.

In a fourteenth aspect based on any one of the tenth to thirteenth aspects, the attribute information includes information indicating the attribute of each pixel of the target image input in the image input step. And

In a fifteenth aspect based on any one of the tenth to thirteenth aspects, the processing for correcting the spatial frequency characteristic comprises:
According to a feature of the present invention, the image processing apparatus includes a process of performing correction on a predetermined region or not performing correction on the basis of the determination result in the image area separation step.

In a sixteenth aspect based on any one of the tenth to thirteenth aspects, the encoding includes JPEG encoding.

According to a seventeenth aspect, a program for causing a computer to realize the functions of the image processing apparatus according to any one of claims 1 to 6 or the functions of the image processing system according to claim 7 is readable by a computer. It is characterized by being recorded on a storage medium.

An eighteenth invention is characterized in that a program for causing a computer to execute the processing steps of the image processing method according to any one of claims 8 to 16 is recorded on a computer-readable storage medium.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] The present invention is applied to, for example, an image processing apparatus 100 as shown in FIG. The image processing apparatus 100 according to the present embodiment reads the image to be processed again if the desired compression ratio cannot be achieved when performing image compression by the JPEG method or the like, and determines the attribute of the target image. Based on the above, a filter processing (spatial frequency characteristic correction processing) is performed when the target image is compressed, whereby image deterioration due to compression is reduced as much as possible, and a high compression ratio is realized. Hereinafter, the image processing apparatus 100 according to the present embodiment will be specifically described.

<Overall Configuration of Image Processing Apparatus 100> The image processing apparatus 100 switches between the input from the image scanner unit 120 and the input from the page description language rendering unit 121 (image input system), as shown in FIG. 130 that outputs the data and a line buffer (block line buffer for compression) that temporarily stores the output of the selector 130
101, an attribute flag encoding unit 102 for encoding attribute flag data from the line buffer 101, and an encoding unit 1 for encoding image data from the line buffer 101
04, the attribute flag encoding unit 102 and the encoding unit 104
A compression buffer 106 for temporarily storing the encoded data (compressed image data and compression attribute flag data) obtained in
A hard disk (HDD) 109 for storing the encoded data stored in the compression buffer 106;
A code amount detection unit 107 for detecting the code amount of the coded data accumulated in 06, and whether or not the code amount obtained by the code amount detection unit 107 is a code amount at a predetermined (desired) compression ratio And the line buffer 1
A determination unit 103 that determines an attribute (image attribute) of an input image based on attribute flag data from 01, and a code amount determination unit 10
8 and a filter processing unit 1 that performs a process of correcting a spatial frequency characteristic at the time of re-encoding based on the determination result of the determination unit 103
05 and encoded data (compressed image data and compression attribute flag data) corresponding to the image in the hard disk (HDD) 109 when the image data in the hard disk (HDD) 109 is printed out by the printer unit 116 or the like. A compression buffer 110 for storing, an attribute flag decoding unit 111 for decoding compressed attribute flag data stored in the compression buffer 110, and a decoding unit 113 for decoding compressed image data stored in the compression buffer 110
Determining unit 112 for determining the attribute of the image to be processed from the attribute flag data obtained by the attribute flag decoding unit 111
And a decoding unit 113 based on the determination result of the determination unit 112.
A filter processing unit 114 for performing a process of correcting a spatial frequency characteristic on the image data obtained by
The image data after the processing in step 14 is temporarily stored and
And a line buffer (development block buffer) 115 for outputting data to the block 16.

<A series of operations of the image processing apparatus 100> FIG.
9 is a flowchart showing the operation of the image processing apparatus 100 as described above.

Step S201, Step S202: The selector 130 switches the input from the image scanner unit 120 or the input from the page description language rendering unit 121. For example, the selector 130 switches to an input from the image scanner unit 120 when the image processing apparatus 100 functions as a copier, and the page description language rendering unit 121 when the image processing apparatus 100 functions as a printer. Switch to input from.

Here, the image scanner unit 120 has an arbitrary image area separation processing function, and generates, for example, attribute flag data for identifying pixels constituting a black character portion in a document image in pixel units. Is configured. Also,
The page description language rendering unit 121 generates a print image by interpreting the PDL command. At this time, the page description language rendering unit 121 refers to information indicating the type of the command, and, similarly to the image scanner unit 120, generates a pixel constituting a black character portion. Is configured to generate attribute flag data for identifying pixel by pixel.

Accordingly, the selector 130 converts the image data 1001 and the attribute flag data 1003 obtained by the image scanner unit 120 or the image data 1002 and the attribute flag data 1004 obtained by the page description language rendering unit 121 into line data. The data is output via the buffer 101.

It should be noted that the attribute flag data is not limited to those for identifying the pixels constituting the black character portion. For example, the attribute flag data includes a photograph portion, a print portion, a color character portion, a thin line portion, a halftone dot portion, It is also possible to use multi-bit information indicating various attributes such as a vector graphics section as attribute flag data.

Step S203: The encoding unit 104 encodes the image data output from the line buffer 101 and temporarily stores it as compressed image data (encoded data) in the compression buffer 106, as will be described in detail later. In addition, the attribute flag encoding unit 102
The attribute flag data output from 1 is encoded and temporarily stored in the compression buffer 106 as compressed attribute flag data (encoded data).

Steps S204 and S205: The code amount detection unit 107 calculates the code amount of the compressed image data stored in the compression buffer 106. Then, the code amount determination unit 108 determines whether or not the code amount obtained by the code amount detection unit 107 is a code amount at a predetermined (desired) compression ratio.

Step S207: If the result of the determination by the code amount determining unit 108 indicates that the code amount is at a predetermined (desired) compression rate, the encoded data stored in the compression buffer 106 is stored in the hard disk 109. Is done.

Steps S206 and S207: If the result of the determination by the code amount determining unit 108 is that the code amount is not at a predetermined (desired) compression rate, the selector 130
The image data and the attribute flag data are obtained again from the image scanner 120 or the page description language rendering unit 121 and output. The image data and the attribute flag data at this time are supplied to the attribute flag encoding unit 102 and the encoding unit 104 via the line buffer 101 and are processed. At this time, although the details will be described later, the filter processing unit (spatial filter processing unit) 105 executes a process of correcting the spatial frequency characteristics of the image data. After that, the coded data after the correction processing accumulated in the compression buffer 106 is stored in the hard disk 109.

Step S208: For example, when the image stored in the hard disk 109 is printed out from the printer unit 116, the compressed image data and the compressed attribute flag data stored in the hard disk 109 are temporarily output to the compression buffer 110. Is accumulated.

The attribute flag decoding unit 111 reads out the compressed attribute flag data from the compression buffer 110 and decodes the data. Further, the decoding unit 113 reads out the compressed image data from the compression buffer 110 and decodes the same by setting an inverse quantization matrix corresponding to the encoding unit 104, for example.
The determining unit 112 determines the attribute of the image to be processed based on the decoded attribute flag data obtained by the attribute flag decoding unit 111. The filter processing unit 114 performs spatial frequency characteristic correction processing on the decoded image data obtained by the decoding unit 113 based on the determination result of the determination unit 112, which will be described in detail later.

Step S209: Filter processing section 114
The image data after the processing in
Is output from the printer unit 116 through the printer.

<Encoding and Decoding in Image Processing Apparatus 100> FIG. 3 shows an internal configuration of the encoding unit 104 and the decoding unit 113 shown in FIG. Encoding unit 1
As shown in FIG. 3, the block 04 includes a color conversion unit 301, a discrete cosine transform (DCT) unit 302, a quantization unit 304, and a variable length coding (VLC) unit 304. The decoding unit 113 includes a variable length decoding (VLD) unit 306, an inverse quantization unit 307, a DCT inverse transform (IDCT) unit 308, and a color conversion unit 309.

First, in the encoding unit 104, the input image from the selector 130 is supplied to the color conversion unit 301. The input image here is, for example, a color image signal, which is a signal of three colors of red (R), green (G), and blue (B) and a signal of 256 gradations (RGB image signal). Therefore, the color conversion unit 301 converts the RGB image signal into a luminance / color difference signal (YCbC
r signal).

The discrete cosine transform (DCT) unit 302
Each of the luminance and chrominance signals obtained by the color conversion unit 301 is subjected to spatial frequency conversion (DCT conversion) in units of 8 × 8 pixels. The quantization unit 303 uses a preset quantization matrix to obtain the DT obtained by the DCT transformation unit 302.
By quantizing the CT coefficients, the data amount of the target image data is reduced. The variable length encoder (VLC) unit 304
By subjecting the quantized value obtained by the quantizing unit 303 to Huffman coding, the data amount of the target image data is further reduced.

As described above, the encoded data (compressed image data) obtained by the encoding unit 104 is stored in the hard disk 109 (or the compression buffer 106).

When decoding the compressed image data stored in the hard disk 109 (or the compression buffer 106), the variable length decoding (VLD) unit 306 in the decoding unit 113 transmits the data to the hard disk 109 (or the compression buffer 1).
06), the target compressed image data is read, and Huffman decoding (decoding) is performed. The inverse quantization unit 307 returns the data after processing in the variable length decoding (VLD) unit 306 to a DCT coefficient value using a preset inverse quantization matrix. The inverse DCT transform unit 308 includes an inverse quantization unit 307
By performing a DCT inverse transform on the DCT coefficient value obtained in the above, a luminance / color difference signal is obtained. The color conversion unit 309
The luminance and chrominance signals obtained by the inverse DCT converter 308 are
Return to image signal.

Therefore, the color conversion unit 3 of the decoding unit 113
09, the RGB image signal (color image signal)
Print output is performed by the printer unit 116.

<Re-encoding in Image Processing Apparatus 100> FIG.
Is a diagram illustrating the configuration of re-encoding based on the result of code amount detection in the image processing apparatus 100 according to the present embodiment.

First, the code amount detection unit 107 calculates the code amount of the compressed image data stored in the compression buffer 106. The code amount determination unit 108 determines whether or not a desired compression rate is obtained from the code amount obtained by the code amount detection unit 107.

As a specific method of determining the code amount in the code amount determination unit 108, for example, it is assumed that the size of the original input image data is 40 MB and the desired compression ratio is 1/4. In this case, the size of the compressed image data is 10
It must be less than or equal to MB. Therefore, it is sufficient to determine whether the size of the actually obtained compressed image data is 10 MB or less. The compression ratio is 1 /
The compression ratio is not limited to 4, and an arbitrary compression ratio can be applied.

As a result of the determination by the code amount determination section 108, if the desired compression ratio has been achieved, the compressed image data at this time is stored in the hard disk 109.

On the other hand, if the result of the determination by the code amount determining unit 108 is that the desired compression ratio has not been achieved, the selector 1
Reference numeral 30 reads an image again from the image scanner unit 120 or the page description language rendering unit 121 (inputs an image again).

The image data (and the attribute flag data) input again by the selector 130 are encoded by the encoding unit 104 and the attribute flag encoding unit 102. At this time, the filter processing unit 105 The image data is subjected to a spatial filtering process described later in detail. Therefore, the encoding unit 104 encodes the image data that has been subjected to the spatial filter processing by the filter processing unit 105.

Encoding section 104 and attribute flag encoding section 1
02, that is, the encoded data at a desired compression ratio is stored in the hard disk 109 via the compression buffer 106.

<Filter Processing in Image Processing Apparatus 100>
FIG. 5 shows an example of a filter coefficient of a spatial filter process (a process of correcting a spatial frequency; hereinafter, also simply referred to as a “filter process”) performed by the filter processing unit 105. The filter processing unit 105 performs a filtering process (smoothing process, smoothing process, enhancement process) on the image data before encoding using the filter coefficients in FIG. 5 described above to improve the image compression ratio.

Incidentally, the filter coefficients are not limited to those shown in FIG. 5, and any coefficients can be applied.
Further, in the filter processing unit 105, for example, based on attribute flag data (result of image area separation), filter processing is performed on a predetermined area (photograph area or the like), or a predetermined area (black characters, color characters, fine lines) , Etc.), the filter processing may not be performed.

<Quantization in Image Processing Apparatus 100> FIG.
(A) and (b) show an example of a quantization matrix for DCT coefficients in units of 8 × 8 pixels used in the encoding unit 104 (specifically, the quantization unit 303). FIG. 6A shows a quantization matrix T1 used in the first quantization, and FIG. 6B shows a quantization matrix T2 used to increase the compression ratio at the time of re-encoding. . If compression is performed at T1 and a desired compression ratio cannot be achieved, compression is performed using T2 as a specific matrix for coarsening the quantization step, so that image degradation is conspicuous. The matrix can be set arbitrarily instead of T1 and T2. In the present invention, since the quantization matrix is not changed, image degradation can be reduced.

In the present embodiment, when a desired compression ratio cannot be obtained, image data is input again, and
The input image data is subjected to the filtering process and configured to perform re-encoding.For example, before performing the first encoding, the filtering process is performed on the image data, and the image data is It may be used at the time of re-encoding. In addition, basically, it is not necessary to change the quantization matrix, but if a higher compression ratio is required, perform filtering and then compress the quantization matrix into a matrix with high compression. Is also possible.

[Second Embodiment] In the first embodiment, when re-encoding is performed in the image processing apparatus 100 shown in FIG. 1, filter processing is performed before the encoding. Configured. In the present embodiment, in the image processing apparatus 100 of FIG. 1, the filtering process is performed within M × N pixels, and encoding is performed within M × N pixels. In addition, at least two or more filters for the filtering process are prepared, and the filter to be applied is switched according to the characteristics of the target area.

Specifically, for example, the line buffer 10
In step 1, the input image data is divided into tiles (blocks) of M × N pixels and output. The coding unit 104 and the attribute flag coding unit 102 perform discrete cosine transform coding (JPEG coding) of image data and run-length coding of attribute flag data for each block of M × N pixels.

Here, the block sizes “M” and “N” are multiples of the window size (block size) in the discrete cosine transform coding. For example, in JPEG encoding, the window size is set to 8 × 8 pixels, and “M” = “N” = 32. In this case, in JPEG encoding, a block of 32 × 32 pixels is further divided into blocks of 8 × 8 pixels, and
Encoding is performed in units of × 8 pixel blocks.

Accordingly, the encoding unit 104 converts the 16 8 × 8 pixel windows included in the 32 × 32 pixel block image from the line buffer 101 into
A so-called DCT process is performed to quantize. The quantization coefficient (quantization matrix) used at this time can be switched and set for each block of M × N pixels, and this switching signal is input to the attribute flag encoding unit 102.

Referring to the attribute flag data of 32 × 32 pixels corresponding to the image data, the determination unit 120 performs a determination process described later, generates a quantization coefficient selection signal, and sends it to the determination unit 103. The attribute flag data is attached to each pixel. However, as in the present invention, since the encoding method in the M × N pixel tile is fixed, the attribute flag data in the tile is converted by the attribute flag encoding unit 102. It is necessary to analyze and determine the attribute representative of the tile.

Here, it is determined whether or not a character is included in the tile. If at least one character attribute flag is included in a 32 × 32 pixel tile, it is determined that a character is included. Alternatively, the number of pixels of the attribute flag data having the character attribute may be counted in the tile, and it may be determined that the tile includes a character only when the number exceeds a predetermined threshold value.

When performing re-encoding, the filter processing unit 105 performs, for example, a filtering process in consideration of character characteristics on a character region based on the attribute flag data, Performs filter processing that is appropriate for the region.

The image processing apparatus 100 according to the first and second embodiments may be used by connecting to a computer, an image input device, and an image output device, for example, as shown in FIG. It is possible. In this case, the computer and the image input device function as an image input system for inputting an image to be encoded, and the image output device functions as an image output system for decoding and printing out the encoded image. .

Another object of the present invention is to supply a storage medium storing program codes of software for realizing the functions of the host and the terminal according to the first and second embodiments to a system or an apparatus, and to provide the system or apparatus with the storage medium. It is needless to say that the present invention is also achieved when the computer (or CPU or MPU) of the apparatus reads out and executes the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the first and second embodiments, and the storage medium storing the program code constitutes the present invention. ROM, floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, C
A D-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, or the like can be used. The functions of the first and second embodiments are realized by executing the program code read by the computer, and the OS running on the computer based on the instruction of the program code. It goes without saying that the present invention includes a case in which the functions of the first and second embodiments are realized by performing part or all of the actual processing. Further, after the program code read from the storage medium is written to a memory provided in an extension function board inserted into the computer or a function extension unit connected to the computer, the function extension is performed based on the instruction of the program code. C provided on board and function expansion unit
It goes without saying that the PU or the like performs part or all of the actual processing, and the processing realizes the functions of the first and second embodiments.

FIG. 8 shows a function 600 of the computer. For example, the image processing device cost 100 is
It has the computer function 600 shown in FIG. 8 described above, and the operation in the first and second embodiments is performed by the CPU 601.

As shown in FIG. 8, the computer function 600 includes a CPU 601, a ROM 602, and a RAM 6
03, a keyboard controller (KBC) 605 of a keyboard (KB) 609, and a CRT controller (CR) of a CRT display (CRT) 610 as a display unit.
TC) 606, a hard disk (HD) 611 and a disk controller (DKC) 607 of a floppy disk (FD) 612, and a network interface card (NIC) 608 communicably connected to each other via a system bus 604. And

The CPU 601 has a ROM 602 or an HD
By executing the software stored in the 611 or the software supplied from the FD 612, each component connected to the system bus 604 is generally controlled.
That is, the CPU 601 stores a processing program according to the processing sequence shown in FIG.
2, or by reading and executing from the HD 611 or the FD 612, the control for realizing the operation in the first and second embodiments is performed.

The RAM 603 functions as a main memory or a work area of the CPU 601. KBC605
Controls an instruction input from the KB 609 or a pointing device (not shown). CRTC 606 uses C
The display of the RT 610 is controlled. The DKC 607 includes a boot program, various applications, editing files,
It controls access to the HD 611 and FD 612 that store a user file, a network management program, and the above-described processing programs in the first and second embodiments. The NIC 608 bidirectionally exchanges data with other devices on the network 140 (computers, image input devices, image output devices, and the like as shown in FIG. 7).

[0070]

As described above, according to the present invention, when a target image (such as a color image) is coded (encoded by the JPEG method or the like), the code amount is reduced to a predetermined code amount (compression ratio). If the target image has not been reached, the target image is input again to perform encoding. At this time, the spatial frequency characteristic is corrected for the target image. Regarding this correction, the attribute of the area in the target image, which is input together with the target image (the attribute for identifying the pixels constituting the black character portion, the color character portion, the thin line, the photograph portion, the print portion, etc. in the target image) May be performed on the basis of an attribute flag indicating. For example, a correction process is performed on a region of a photograph portion, but a black character portion, a color character portion,
Correction processing is not performed on a region including many edges such as fine lines. With such a configuration, quantization can be performed without changing the quantization coefficient (quantization matrix) in encoding, so that a desired compression rate can be achieved, and image compression in which image degradation is minimized. Can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image processing apparatus to which the present invention has been applied.

FIG. 2 is a flowchart for explaining the overall operation of the image processing apparatus.

FIG. 3 is a block diagram illustrating a configuration of encoding and decoding of the image processing apparatus.

FIG. 4 is a block diagram illustrating a configuration of filter processing and re-encoding of the image processing apparatus.

FIG. 5 is a diagram for explaining an example of a filter coefficient of the filter processing.

FIG. 6 is a diagram illustrating an example of a quantization matrix in the above encoding.

FIG. 7 is a diagram illustrating a connection example of the image processing apparatus.

FIG. 8 is a block diagram illustrating an example of a computer function of the image processing apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 image processing device 101 line buffer 102 attribute flag encoding unit 103 determination unit 104 encoding unit 105 filter processing unit 106 compression buffer 107 code amount detection unit 108 code amount determination unit 109 hard disk 110 compression buffer 111 attribute flag decoding unit 112 determination Unit 113 decoding unit 114 filter processing unit 115 line buffer 116 printer unit 120 image scanner unit 121 page description language rendering unit 130 selector

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C059 KK01 MA00 MA23 MC14 ME02 PP01 PP15 PP16 PP19 PP20 RC11 RC37 SS28 TA47 TA69 TB08 TB10 TC20 TC38 TD12 UA02 UA05 UA34 5C077 LL19 PP02 PP27 PP28 PP32 PP49 PQ08 TT06 5C078 BA44 DA01 DA02

Claims (18)

[Claims] 1. An image input unit for inputting a target image, an encoding unit for encoding the target image input by the image input unit, and a code of encoded data of the target image obtained by the encoding unit A code amount detecting unit for detecting the amount, and a target image input by the image input unit,
An image processing apparatus comprising: a first spatial frequency correction unit that corrects a spatial frequency characteristic, wherein the image input unit inputs a target image again based on a detection result of the code amount detection unit, The first spatial frequency correction means corrects the spatial frequency characteristic for the target image input again by the image input means, and the encoding means corrects the target image after the correction by the first spatial frequency correction means. An image processing apparatus for encoding a target image. 2. The image input means according to claim 1, further comprising:
2. The method according to claim 1, wherein an attribute flag indicating an attribute of a region in the target image is input, and wherein the first spatial frequency correction unit corrects the spatial frequency characteristic based on the attribute flag. Image processing device. 3. The apparatus according to claim 2, wherein the first spatial frequency correction means corrects different spatial frequency characteristics for each predetermined area included in the target image based on the attribute flag. Image processing device. 4. A decoding means for decoding coded data of a target image obtained by said coding means, and a first image obtained by decoding said target image obtained by said decoding means. 2. The image processing apparatus according to claim 1, further comprising a first spatial frequency correction unit that corrects a spatial frequency characteristic corresponding to the spatial frequency correction unit. 5. The first spatial frequency correction unit corrects the spatial frequency characteristic within M × N pixels of the target image, and the encoding unit corrects the spatial frequency characteristic by the first spatial frequency correction unit. 2. The image processing apparatus according to claim 1, wherein the encoding is performed on a subsequent target image by selecting a quantization coefficient to be applied within M * N pixels. 6. The image processing apparatus according to claim 1, wherein said encoding means performs encoding according to a JPEG system. 7. An image processing system in which a plurality of devices are communicably connected to each other, wherein at least one of the plurality of devices is the image processing device according to claim 1. An image processing system having the following functions. 8. An image processing method for encoding an arbitrary image, comprising: an encoding step of encoding an input target image; and a code amount of encoded data of the target image obtained in the encoding step. A re-input step of re-inputting the target image based on the detection result in the re-input step, and a spatial frequency for the re-input target image in the re-input step. A spatial frequency correction step of correcting characteristics, and wherein the encoding step includes a step of encoding the target image after the correction by the spatial frequency correction step. 9. The spatial frequency correction step includes a step of correcting the spatial frequency characteristic based on an attribute flag input together with the target image and indicating an attribute of a region in the target image. An image processing method according to claim 8. 10. An image input step of inputting a target image, an encoding step of encoding the target image input in the image input step, and decoding encoded data of the target image obtained in the encoding step And an image output step of outputting a decoded target image obtained in the decoding step, the image processing method comprising: An image area separating step of determining an attribute of a region; a code amount detecting step of detecting a code amount of encoded data of the target image obtained in the encoding step; and a predetermined amount based on a detection result in the code amount detecting step. A code amount determination step of determining whether or not the code amount of has been achieved, based on the determination result in the code amount determination step, A re-input control step of controlling whether re-input of the target image is performed by the image input step; and performing the encoding in the encoding step by re-input of the target image by the re-input control step, the image area separating step A spatial frequency correction step of correcting different spatial frequency characteristics for each region included in the target image based on the determination result in the step (a). 11. An image input step for inputting a target image, an encoding step for encoding the target image input in the image input step, and decoding of encoded data of the target image obtained in the encoding step And an image output step of outputting a decoded target image obtained in the decoding step, the image processing method comprising: An image area separating step of determining an attribute of a region; a code amount detecting step of detecting a code amount of encoded data of the target image obtained in the encoding step; and a predetermined amount based on a detection result in the code amount detecting step. A code amount determination step of determining whether or not the code amount of has been achieved, based on the determination result in the code amount determination step, A re-input control step of controlling whether re-input of the target image is performed by the image input step; and performing the encoding in the encoding step by re-input of the target image by the re-input control step, the image area separating step A first spatial frequency correction step of correcting different spatial frequency characteristics for each region included in the target image based on the determination result in the above, and a re-input of the target image in the re-input control step in the encoding step. When performing encoding, a second spatial frequency characteristic that is different for each area included in the decoded target image obtained in the decoding step is corrected based on the determination result in the image area separation step. A spatial frequency correction step. 12. An image input step of inputting a target image, an encoding step of encoding the target image input in the image input step, and decoding encoded data of the target image obtained in the encoding step And an image output step of outputting a decoded target image obtained in the decoding step, the image processing method comprising: An image area separation step of determining an attribute of a region; an attribute processing step of statistically processing information of the attribute in the image area separation step within a pixel block of a predetermined size set in advance; Selecting a quantization coefficient in the encoding step in the pixel block of the predetermined size based on the processing result of A code amount detecting step of detecting the code amount of the encoded data of the target image obtained in the encoding step; and determining whether or not a predetermined code amount has been achieved based on a detection result in the code amount detecting step. A code amount determination step to perform, based on the determination result in the code amount determination step, a re-input control step of controlling whether to re-input the target image in the image input step, When performing encoding in the encoding step by re-input, a spatial frequency correction step of correcting different spatial frequency characteristics for each region included in the target image based on the determination result in the image area separation step. An image processing method comprising: 13. An image input step of inputting a target image, an encoding step of encoding the target image input in the image input step, and decoding encoded data of the target image obtained in the encoding step And an image output step of outputting a decoded target image obtained in the decoding step, the image processing method comprising: An image area separation step of determining an attribute of a region; an attribute processing step of statistically processing information of the attribute in the image area separation step within a pixel block of a predetermined size set in advance; Selecting a quantization coefficient in the encoding step in the pixel block of the predetermined size based on the processing result of A code amount detecting step of detecting the code amount of the encoded data of the target image obtained in the encoding step; and determining whether or not a predetermined code amount has been achieved based on a detection result in the code amount detecting step. A code amount determining step of performing, based on the determination result in the code amount determining step, a re-input control step of controlling whether to perform re-input of the target image in the image input step; and When encoding is performed in the encoding step by re-input, first spatial frequency correction for correcting spatial frequency characteristics different for each region included in the target image based on the determination result in the image area separation step A step of performing the encoding in the encoding step by re-inputting the target image in the re-input control step; A second spatial frequency correction step of correcting different spatial frequency characteristics for each region included in the decoded target image obtained in the decoding step based on the determination result of Image processing method. 14. The image processing method according to claim 10, wherein the attribute information includes information indicating an attribute of each pixel of the target image input in the image input step. . 15. The method as claimed in claim 15, wherein the correction processing of the spatial frequency characteristic includes a processing of correcting or not performing a correction on a predetermined area based on a determination result in the image area separation step. 14. The image processing method according to any one of 10 to 13. 16. The image processing method according to claim 10, wherein the encoding includes JPEG encoding. 17. A computer-readable storage medium storing a program for causing a computer to realize the functions of the image processing apparatus according to claim 1 or the functions of the image processing system according to claim 7. . 18. A computer-readable storage medium storing a program for causing a computer to execute the processing steps of the image processing method according to claim 8.