JPH10294859A - Image processing unit, image processing method, image reader, copying machine and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image with high image quality even in the case of magnification and reduction when both digital filter processing and magnification reduction processing are applied to an input image. SOLUTION: When a high magnification reduction rate SCR higher than a threshold level TH is designated by a UI (user interface) 2, a select signal generating section 67 outputs a selection signal SL to select an A input and each of selectors 64-66 selects the A input. Thus, image data are processed in the order of digital filter processing and magnification reduction processing. On the other hand, when the UI 2 designates a magnification reduction rate SCR lower than the threshold level TH, the select signal generating section 67 outputs a selection signal SL to select a B input and each of the selectors 64-66 selects the B input. Thus, the image processing is applied to the image data in the order of magnification reduction processing and digital filter processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image processing apparatus,
The present invention relates to an image processing method, an image reading device, a copying machine, and a recording medium.

[0002]

2. Description of the Related Art In a digital copying machine or the like, when a document is read by a document reading unit, the read image is converted into a digital value, shading correction is performed, and digital filter processing and enlargement / reduction processing are performed as necessary. Or In the shading correction, density unevenness caused by a document illumination light source, a reading lens, a line sensor, and the like is corrected. In digital filter processing, filter processing is performed according to the type of the document. That is, in the case of a photographic original, it is desirable that the density changes smoothly. Therefore, a smoothing filter process for reducing high-frequency components is performed. On the other hand, in the case of a character original, it is desirable that the characters appear clearly, so that an edge emphasizing filter process for emphasizing high frequency components is performed. In the enlargement / reduction processing, the image is enlarged / reduced by interpolation or thinning out of pixels. As a prior art relating to an apparatus for performing such processing, for example, JP-A-3-40179 or JP-A-2-132
No. 967 is known.

[0003]

By the way, in a configuration in which digital filter processing is performed after the enlargement / reduction processing as disclosed in, for example, Japanese Patent Application Laid-Open No. H3-40179, it is possible to perform edge enhancement processing using a digital filter after enlargement processing. However, since the frequency of the edge portion of the character is lowered by the density interpolation in the enlargement process, there is a problem that the edge is not emphasized and the image becomes blurred. On the other hand, for example,
In a configuration in which enlargement / reduction processing is performed at a stage subsequent to digital filter processing as in No. 32967, pixels are thinned out by reduction processing after the density difference of each halftone dot pixel is enlarged by edge enhancement processing by the digital filter. Therefore, there is a problem that moire (striped pattern) due to a difference between a halftone dot frequency in a halftone dot reduction process and a cycle of a pixel to be interpolated in the reduction process is emphasized. In order to suppress this moiré, it is conceivable to provide a smoothing filter for lowering the halftone frequency in a stage preceding the enlargement / reduction processing unit. However, in addition to the addition of hardware, the smoothing processing is also performed for the character part. Is performed, the image quality of characters is deteriorated.

The present invention has been made under such a background. When both digital filter processing and enlargement / reduction processing are performed on an input image, a high-quality image is obtained in both enlargement and reduction. It is intended to provide you with the ability.

[0005]

In order to solve the above-mentioned problems, the present invention provides an enlargement / reduction section for performing an image enlargement or reduction process on input digital image data at a designated enlargement / reduction ratio; A digital filter unit for performing a smoothing or edge emphasizing filter process on the digital image data according to the type of the image. It is characterized by comprising switching means for switching which of the scaling unit and the digital filter unit is executed first.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. A: Embodiment (1) Overall Configuration of Embodiment FIG. 1 is a block diagram showing the overall configuration of a digital copying machine according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a control unit including a microprocessor or the like, and a bus BU.
It controls each part of the device connected via S. Reference numeral 2 denotes a UI (user interface) for receiving an input operation;
The control unit 1 includes a liquid crystal panel that displays menu display information and various setting information supplied from the control unit 1, and a touch panel sensor that detects an input operation. Through the UI 2, the operator performs a copy instruction, a designation of a document type (a text document or a photo document), an input of a scaling ratio (hereinafter, referred to as a scaling ratio SCR), and the like. Note that, in the present embodiment, a photo original means a document which is not a character original or which does not mainly include characters.

[0007] Reference numeral 3 denotes a CCD (Charge Coupled Device).
e) A sensor that scans a document image in cooperation with a light source (not shown) to generate an image signal. Reference numeral 4 denotes an A / D (analog / digital) converter, which converts an input image signal generated by the CCD sensor 3 into 8-bit digital image data representing a density value of 256 gradations. Reference numeral 5 denotes a shading correction unit that corrects density unevenness of input image data generated when reading an image.

Reference numeral 6 denotes an image processing unit which performs edge enhancement processing or smoothing processing of the image data according to the type of the original specified by the UI 2 and enlarges the image data according to the scaling ratio SCR specified by the UI 2. Perform processing or reduction processing. Details of the image processing unit 6 will be described later.

Reference numeral 7 denotes a page memory, which is a RAM (Random Access Memory) for bitmap-developing the input image data processed by the image processing unit 6 in page units.
emory). This digital copying machine has an image processing unit 6
There is a mode in which the input image data processed by the above is directly output, and a mode in which the input image data is temporarily stored in the page memory 7 and read and output as needed.

Reference numeral 8 denotes a gamma correction unit, which outputs image data supplied directly from the image processing unit 6 or image data read from the page memory 7 to an image output unit 10 described later.
Is performed so as to match the characteristics of (1). Reference numeral 9 denotes a screen generation unit that exposes the photoconductor based on image data supplied from the page memory 7 via the gamma correction unit 8, and forms an electrostatic latent image corresponding to the image data. An image output unit 10 forms a toner image corresponding to the electrostatic latent image on a photoconductor, transfers the toner image to a printing medium such as paper, fixes the toner image, and outputs the image.

(2) Details of Image Processing Unit 6 Next, details of the image processing unit 6 will be described. FIG. 2 is a block diagram illustrating a configuration of the image processing unit 6. In the figure, reference numeral 61 denotes a digital filter unit, which performs edge enhancement processing or smoothing processing of image data according to the type of document specified on the UI 2. An enlargement / reduction unit 62 performs enlargement or reduction processing of image data according to the enlargement / reduction ratio SCR specified on the UI 2. Each of the digital filter unit 61 and the enlargement / reduction unit 62 includes a line buffer (described later) that stores input image data in units of lines as a work area. The details of the digital filter section 61 and the scaling section 62 will be described later.

Reference numerals 64 to 66 denote selectors, respectively, A and B
Either one of the image data input from the two input terminals is used as the selection signal SL supplied from the selection signal generation unit 67.
Select and output according to. The output of the shading correction unit 5 is supplied to the input terminal A of the selector 64 and the input terminal B of the selector 65. The output of the selector 64 is input to the digital filter unit 61, and the output of the selector 65 is input to the scaling unit 62. Further, the output of the digital filter section 61 is input to the input terminal A of the selector 65 and the input terminal B of the selector 66. On the other hand, the output of the scaling unit 62 is connected to the input terminal B of the selector 64 and the selector 66.
Is input to the input terminal A of the. The output of the selector 66 is supplied to the page memory 7 or the gamma correction unit 8 shown in FIG.
Is forwarded to

In FIG. 2, select signal generating section 67
Compares the enlargement / reduction ratio SCR specified in the UI 2 with the threshold value TH set in the threshold value setting unit 68, and supplies a selection signal SL to each of the selectors 64 to 66 according to the comparison result. That is, the designated scaling ratio SC
When R is higher than the threshold value TH, each of the selectors 64-66
Outputs a selection signal SL that causes the selectors 64 to 66 to select the B input when the designated scaling ratio SCR is lower than the threshold value TH.

With such a configuration, when the enlargement / reduction ratio SCR higher than the threshold value TH is specified in the UI 2, the selection signal S for selecting the A input from the selection signal generation unit 67 is selected.
L is output, and each of the selectors 64-66 selects the A input. Accordingly, the image data supplied from the shading correction unit 6 follows the path of the selector 64, the digital filter unit 61, the selector 65, the scaling unit 62, and the selector 66. As a result, the image data is subjected to image processing in the order of digital filter processing and enlargement processing. Note that the enlargement process here is an enlargement process in the sense that the enlargement / reduction ratio SCR is higher than the threshold value TH. When the set threshold value TH is lower than 100%, some of the reduction processes are performed. Is also included.

On the other hand, when the enlargement / reduction ratio SCR lower than the threshold value TH is designated in the UI 2, the select signal generator 6
7, a selection signal SL for selecting the B input is output, and each of the selectors 64 to 66 selects the B input. This allows
The image data supplied from the shading correction unit 6 is
The path of the selector 65, the scaling unit 62, the selector 64, the digital filter unit 61, and the selector 66 is followed. As a result, the image data is subjected to image processing in the order of reduction processing and digital filter processing. Here, the reduction process is a reduction process in the sense that the enlargement / reduction ratio SCR is lower than the threshold value TH. When the set threshold value TH is higher than 100%, a part of the enlargement process is performed. Is also included.

(3) Details of Digital Filter Unit 61 Next, details of the digital filter unit 61 will be described. FIG. 3 is a block diagram showing a configuration of the digital filter unit 61. In the figure, 611 and 612 are FIs.
FO (First-In-First-Out Memory), where each input pixel is 1
The data is stored for the number of lines, and output with a delay corresponding to the time corresponding to one line. The FIFOs 611 and 612 correspond to the line buffers included in the digital filter unit 61 described above. Reference numerals 613 to 618 denote input pixels for one clock (1
This is a latch that delays by a time corresponding to a pixel. First, an input pixel is input to the FIFO 611 and the latch 613. The FIFO 611 outputs the input pixel to the FIFO 612 and the latch 615 after delaying the input pixel by one line.
The FIFO 612 outputs the input pixel to the latch 617 after further delaying the input pixel by one line. On the other hand, the latches 613 and 61
5, 617 delays each input pixel by one clock and then outputs to the latches 614, 616, 618. The latches 614, 616, 618 further delay each input pixel by one clock and output.

Thus, the input image data is 3 × 3
Are generated. That is, as shown in FIG. 4, 1 is determined by the output d02 of the FIFO 612, the output d01 of the latch 617, and the output d00 of the latch 618.
The three pixels on the line are formed, and the output d of the FIFO 611
12, the output d11 of the latch 615 and the output d10 of the latch 616 constitute the third pixel on the second line, and the pixel d22 input last and the output d21 of the latch 613
And the output d20 of the latch 614 forms the third pixel on the third line. FIG. 5 is a time chart showing a process of generating such a pixel window. In the figure, Di, j represents the constituent pixels of the window, i represents the line number, and j represents the column number.
As shown in this figure, the pixel window W sequentially transitions each time a new input pixel Di, j is supplied.

Returning to FIG. 3, the latter stage of the circuit will be described. In the figure, adders 621 to 623, a divider 62
4,625, the multipliers 626 to 628 and the limit circuit 629 are the 3 × 3
Are subjected to smoothing or edge emphasis processing in accordance with preset filter coefficients a to c.
The filter coefficients a to c correspond to the respective constituent pixels of the pixel window shown in FIG. 4 as shown in FIG. 6. In the case of smoothing and the case of edge enhancement, for example, the values as shown in FIG. Is set.

FIG. 8 is a time chart showing the operation at the subsequent stage of the circuit. Hereinafter, the operation of the subsequent stage of the circuit will be described with reference to FIGS. First, the values of the pixels d20, d00, d02, and d22 constituting the window are added in the adder 621 (signal dataCi), and further shifted by 2 bits by the divider 624 to be multiplied by 1/4 (signal dataCi). / 4). Similarly,
Pixels d12, d21, d10 constituting a window
And the value of d01 are added in an adder 621 (signal dataBi), and are shifted by 2 bits by a divider 625 to be multiplied by 1/4 (signal data).
Bi / 4).

The output dataCi of the divider 624 is
/ 4 is multiplied by the coefficient c in the multiplier 626 (signal dCi), and the output data Bi / 4 of the divider 625 is multiplied by the coefficient b in the multiplier 628 (signal dB).
i). The value of the pixel d11 at the center of the window (signal d
ataAi) is multiplied by a coefficient a in a multiplier 627 (signal dAi). Furthermore, these multipliers 626-6
The outputs dCi, dBi, dAi of 28 are added in an adder 629 (dOUTi) and output via a limit circuit 629 (dOi). The limit circuit 629 limits the output dOUTi of the adder 269 as follows. That is, if dOUTi> 255,
When dOi = 255 and dOUTi <0, dOi = 255.
Set to 0.

As described above, in the digital filter section 61, when the document type specified in the UI 2 is a photo document, the filter coefficients a to c corresponding to the smoothing (FIG. 7)
) Is set, and a smoothing process is performed to express the image smoothly. On the other hand, when the specified document type is a text document, filter coefficients a to c (see FIG. 7) corresponding to edge emphasis are set, and edge emphasis processing is performed so as to express the outline of the character sharply.

(4) Details of the enlargement / reduction unit 62 Next, the details of the enlargement / reduction unit 62 will be described with reference to FIGS. FIG. 9 is a block diagram showing the configuration of the enlargement / reduction unit 62, and FIGS. 10 to 12 are timing charts showing the operation of the enlargement / reduction unit 62. In FIG. 9, the scaling unit 62 includes:
Clock generation / timing control section 651, 2-input 2-output selectors 661, 662, 2-input / 1-output selector 6
63 to 666, a write address counter 671, a read address counter 672, SRAMs 673 and 674, buffers 675 and 676, an interpolation circuit 680, and a gate 690.
It is constituted by.

The clock generation / timing control unit 651 includes a pixel clock VCLK for timing one pixel,
A line signal VVLD for timing one line, and gate control signals IMVLD and D for timing image output.
VLD and scaling ratio SCR specified in UI2
Is entered. Then, the clock generation / timing control unit 651 outputs the pixel clock VCLK to the input terminal A of the selector 661, and outputs the clock VCLK ′ obtained by thinning out the pulse of the pixel clock VCLK to the input terminal B of the selector 662 in accordance with the scaling ratio SCR. Output (see FIG. 10). This figure shows a case where the scaling ratio SCR is 150% or 66%.

The selector 661 is supplied with a selection signal E / R which is controlled by either enlargement / reduction (in this case, whether the enlargement / reduction ratio SCR is greater than 100%). Based on the selection signal E / R, a selector 661 is selected.
Outputs the A input (pixel clock VCLK) to the write address counter 671 and the B input (decimated clock VCLK ′) to the read address counter 67
Output to 2. On the other hand, in the case of reduction, the B input (thinned-out clock VCLK ') is written to the write address counter 671.
And outputs the A input (pixel clock VCLK) to the read address counter 672.

The write address counter 671 is an SRAM
A read address counter 672 is a counter that counts up write addresses for the write addresses 672 and 674.
Is a counter for counting up a read address for the SRAMs 673 and 674. Where SRA
M673 and 674 are line buffers for storing image data for one line each, and counters 671 and 672
Is cleared line by line.

For example, at the time of enlargement at an enlargement / reduction ratio of 150%, as shown in FIG.
1 counts up according to the pixel clock VCLK, and the read address counter 672 counts up according to the thinned clock VCLK '. As a result, the image data written by sequentially increasing the address of the SRAM 673 (or 674) is read out from the same address once every two times, so that the enlargement is performed at an enlargement / reduction ratio of 150%.

On the other hand, at the time of reduction at the enlargement / reduction ratio of 66%, as shown in FIG.
Performs the count-up according to the thinned clock VCLK ′, and the read address counter 672 performs the count-up according to the pixel clock VCLK. As a result, once every two SRAMs 673 (or 67
4) The image data is written to the same address and is sequentially read out, so that the image data is reduced at a scaling ratio of 66%.

To the selector 662, a timing signal LTIM indicating a line section generated by the clock generation / timing control unit 651 based on the line signal VVLD is supplied as a selection signal. The selector 662 switches the output destination of the A input and the B input in one line cycle according to the selection signal LTIM. Thereby, the SRAMs 673, 6
At 74, a read operation and a write operation are performed alternately for each line. In other words, the next line is written to the SRAM 674 while the SRAM 673 is being read, and the next line is written to the SRAM 673 while the SRAM 674 is being read. Further, the selector 663 selects the selector 662 based on the timing signal LTIM supplied as the selection signal.
A input and B input are alternately switched and output for each line in synchronization with.

The input image data is processed as follows. First, at the time of enlargement, since a density step occurs between a pixel read out a plurality of times and a pixel read out next, a process of interpolating the density between these pixels is performed. On the other hand, at the time of reduction, jaggedness occurs near the pixel to be thinned out by being written to the same address a plurality of times. Therefore, processing for interpolating the density between the pixel to be thinned and the immediately preceding pixel is performed. Will be

At the time of enlargement, the SRAM 67
Since the value of the pixel read out a plurality of times can be known for the first time after reading from 3 (or 674), the density interpolation processing is performed after the reading. That is, at the time of enlargement, the selectors 664 to 666 select the A input based on the selection signal E / R.
66 → buffer 676 (or 677) → SRAM 67
3 (or 674) → buffer 676 (or 677)
→ selector 663 → selector 665 → interpolation circuit 680 →
Following the path from the selector 664 to the gate 690, the density interpolation is performed after the enlargement processing.

On the other hand, at the time of reduction, the SRAM 673
Since the pixels thinned out at the time of writing to (or 674) disappear, the density interpolation processing is performed before the writing. That is, at the time of reduction, the selector 6
Since 64 to 666 select the B input based on the selection signal E / R, the selector 665 → interpolator 680 → selector 666 → buffer 676 (or 677) → SRAM
673 (or 674) → buffer 676 (or 67)
7) → selector 663 → selector 664 → gate 690
After the density interpolation, a reduction process is performed.

Here, the interpolation circuit 680 performs
Regarding the value of the pixel immediately before reading the same address of the SRAM 673 (or 674) a plurality of times and moving to the next address, the average of that value and the value of the next read pixel is taken as the value after density interpolation. On the other hand, in the case of reduction, the value of the pixel immediately before thinning and the value of the pixel to be thinned are averaged to obtain the value after density interpolation. The timing chart shown in FIG. 12 shows an example of the density interpolation in the case of the enlargement at the enlargement / reduction ratio of 300% and the case of the reduction in the enlargement / reduction ratio of 33%, respectively.

(5) Effects of the Embodiment According to the present embodiment, the processing order of the digital filter unit 61 and the enlargement / reduction unit 62 is made variable according to the enlargement / reduction ratio SCR, so that the enlargement / reduction ratio SCR becomes equal to the threshold value. At the time of enlargement in the sense of being higher than TH, image processing is performed in the order of filter processing by the digital filter unit 61 and enlargement processing by the enlargement / reduction unit 62. As a result, blurring of the character due to a decrease in the frequency of the character edge portion due to the density interpolation in the enlargement processing can be reduced. On the other hand, at the time of reduction in the sense that the enlargement / reduction ratio SCR is lower than the threshold value TH, image processing is performed in the order of reduction processing by the enlargement / reduction unit 62 and filter processing by the digital filter unit 61. As a result, it is possible to suppress an increase in the density difference between pixels of a halftone dot that causes moire, and to reduce the moire at the halftone dot portion. As a result, it is possible to improve the image quality during both enlargement and reduction without adding complicated hardware such as a smoothing filter.

B: Modifications The present invention is not limited to the above-described embodiment, and for example, the following various modifications are possible. (1) Different thresholds TH1 and TH2 depending on the type of document (text document or photo document) specified in UI2
And the selected threshold value and scaling ratio SC
It is possible to switch the processing order by comparing R. In this case, as shown in FIG. 13, threshold values TH1 and TH2 corresponding to the type of the original are
8 and a threshold corresponding to the type of the original designated on the UI 2 is selected by the select signal generator 67.
What is necessary is just to be comprised so that it may be supplied.

For example, Japanese Unexamined Patent Publication No. 7-107293 discloses that, in the case of a character original, it is preferable to process the enlargement / reduction unit and the digital filter unit in order, and in the case of a photo original, it is preferable to process the digital filter unit and the enlargement / reduction unit in this order. There is described a technique for switching the processing order according to the type.
Applying this technical idea to the above-described embodiment, a higher threshold value is selected in order to facilitate the order of the enlargement / reduction section and the digital filter section in the case of a character original, and the digital filter section and the enlargement / reduction section in the case of a photo original. In order to make it easier to
What is necessary is just to select the lower threshold value.

If the number of types of originals to be specified is not two as in the embodiment, but is three or more, threshold values TH1, TH2,... Corresponding to each type are stored. It should be kept.

In the case where the attributes of an image are identified in units of an original as in the embodiment, an original in which characters and photographs or pictures are mixed is usually processed as a character image, so that the image quality can be improved. Deterioration is relatively small. However, so-called TI (text / image), which distinguishes a character portion from a photograph or picture portion in one document,
Separation is performed, and the threshold values TH1 and TH2 of the threshold value setting unit 68 are switched at any time based on the result, whereby more detailed processing can be performed. For example, as shown in FIG. 14, two processing systems are provided: a system that performs image processing in the order of the digital filter unit 61 and the scaling unit 62, and a system that performs image processing in the order of the scaling unit 62 and the digital filter unit 61. , The TI separation unit 70 identifies the TI for each predetermined unit of image data, and according to the identification result, the threshold value T of the threshold value setting unit 68 shown in FIG.
H1 and TH2 are switched. In this case, the select signal generator 67 supplies the select signal S to the selector 71 in the cycle in which the TI separator 70 identifies the image data.
EL 'is controlled. Thus, an appropriate threshold value and an enlargement / reduction ratio SCR are compared according to whether or not image data sequentially input for one document is a character portion, and the processing order of image processing is switched according to the comparison result. .

(2) In the case of a photographic original (ie, an original other than text), it is considered preferable to perform image processing in the order of the digital filter unit 61 and the enlargement / reduction unit 62 regardless of the enlargement / reduction ratio SCR. Therefore, for example, as shown in FIG. 15, by supplying information on the type of the original specified on the UI 2 to the select signal generating section 67, the select signal generating section 67 is configured to operate according to the algorithm shown in FIG. Good. That is,
When the type of the original specified on the UI 2 is not a character original, a selection signal SL for selecting the A input is supplied to each of the selectors 64 to 66 regardless of the scaling ratio SCR. on the other hand,
When the type of the document specified on the UI 2 is a character document, the selection signal SL is controlled according to the scaling ratio SCR as in the embodiment.

(3) In the embodiment, the threshold value TH
Is not particularly limited, but if the threshold TH is TH = 1
If it is (100%), the processing order of the digital filter unit 61 and the enlargement / reduction unit 62 is switched depending on the enlargement or reduction in the usual sense. If TH> 1, the threshold value TH
The above-mentioned processing order is switched depending on whether the enlargement / reduction ratio SCR is higher or not. If TH <1, the above-mentioned process is performed depending on whether the enlargement / reduction ratio SCR is lower than the threshold value TH or not. The order is switched. This threshold TH
May be selected by, for example, experimentally examining the best image quality when the processing order is switched at what scale SCR.

(4) The circuits and the like shown in the embodiments are merely examples, and the configurations of these circuits and the like can be appropriately changed within the scope of the present invention.

(5) In the embodiment, an example is shown in which the present invention is configured as a digital copying machine. However, the present invention is not limited to such an embodiment, and for example, an image including a portion corresponding to the image processing unit 6 in the embodiment. It is also possible to configure as an image reading device such as a scanner.

(6) When the processing of the image processing unit 6 in the embodiment is realized by software, a control program for executing the processing is recorded on a recording medium such as a ROM or a floppy disk, and is transmitted via the recording medium. Thus, the control program can be ported to another copying machine or the like.

[0043]

As described above, according to the present invention, when both the digital filter processing and the enlargement / reduction processing are performed on an input image, a high quality image can be obtained in both enlargement and reduction. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a digital copying machine according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an image processing unit in the copying machine shown in FIG.

FIG. 3 is a block diagram illustrating a configuration of a digital filter unit in the image processing unit illustrated in FIG. 2;

FIG. 4 is a conceptual diagram showing a pixel window generated in the digital filter unit shown in FIG.

FIG. 5 is a timing chart for explaining the operation of the digital filter section shown in FIG. 3 at a stage preceding the circuit;

FIG. 6 is a conceptual diagram showing the correspondence between the filter coefficients of the digital filter unit shown in FIG. 3 and the pixel windows shown in FIG.

FIG. 7 is a diagram illustrating specific numerical values of filter coefficients.

8 is a timing chart for explaining the operation of the digital filter section shown in FIG. 3 at a stage subsequent to the circuit.

9 is a block diagram illustrating a configuration of a scaling unit in the image processing unit illustrated in FIG. 2;

FIG. 10 is a timing chart for explaining the operation of the scaling unit shown in FIG. 9;

FIG. 11 is a timing chart for explaining the operation of the scaling unit shown in FIG. 9;

FIG. 12 is a timing chart for explaining density interpolation processing by an interpolation circuit in the scaling unit shown in FIG. 9;

FIG. 13 is a block diagram showing a main part of a modification of the present invention.

14 is a block diagram illustrating a configuration example of an image processing unit when TI separation is applied in the modification illustrated in FIG.

FIG. 15 is a block diagram showing a main part of another modification of the present invention.

FIG. 16 is a flowchart showing an operation algorithm of a select signal generation unit in the modification shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Control part, 2 ... UI, 3 ... CCD, 4 ... A / D converter, 5 ... Shading correction part, 6 ... Image processing part, 7 ...
Page memory, 8: Gamma correction unit, 9: Screen generation unit, 10: Image output unit, 61: Digital filter unit,
62 ... enlargement / reduction part, 64, 65, 66, 71, 661 to 66
6 selector, 67 select signal generator (switching means,
Comparing means, switching control means), 68: threshold setting section (threshold selecting means), 70: TI separating section, 611, 612
... FIFO, 613-618 ... Latch, 621-623
... Adders, 624, 625 ... Dividers, 626-628 ...
Multiplier 629 limit circuit 651 clock generation / timing control unit 671 write address counter
672: Read address counter, 673, 674 ... SR
AM, 675, 676... Buffer, 690.

Claims (12)

[Claims] 1. An enlargement / reduction unit for performing an enlargement / reduction process on an input digital image data at a designated enlargement / reduction ratio, and smoothing or edge emphasizing the digital image data according to the type of the image. An image processing apparatus comprising: a digital filter unit that performs a filtering process according to (1), wherein any of the scaling unit and the digital filter unit is executed first on the digital image data in accordance with the designated scaling ratio An image processing apparatus, comprising: switching means for switching whether to perform image processing. 2. The image processing apparatus according to claim 1, wherein the switching unit includes a comparing unit that compares the designated scaling ratio with a predetermined threshold value, and based on a comparison result by the comparing unit. When the scaling ratio is higher than the threshold, the digital filter unit;
An image processing apparatus, wherein, in the order of the enlargement / reduction unit, when the enlargement / reduction ratio is lower than the threshold value, the processing order is switched so that processing is performed in the order of the enlargement / reduction unit and then the digital filter unit. 3. The image processing apparatus according to claim 2, wherein
The image processing apparatus further comprises threshold value selecting means for setting a different threshold value in the comparing means according to the type of image of the input digital image data. 4. The image processing apparatus according to claim 3, wherein the type of the image is one of a character image and another image. 5. The image processing apparatus according to claim 4, wherein said threshold value selecting means sets a higher threshold value for a character image and a lower threshold value for other images. An image processing apparatus characterized by setting: 6. An enlarging / reducing unit for enlarging or reducing an input digital image data at a designated enlargement / reduction ratio, and smoothing or edge emphasizing the digital image data according to the type of the image. An image processing apparatus comprising: a digital filter unit that performs a filtering process described above, wherein when the image type of the digital image data is not a character image, the digital image data is processed in the order of the digital filter unit, and then the scaling unit. On the other hand, when the type of the image is a character image, which of the enlargement / reduction unit and the digital filter unit is to be executed first on the digital image data according to the designated enlargement / reduction ratio is determined. An image processing apparatus comprising switching control means for switching. 7. An enlarging / reducing process for enlarging or reducing an input digital image data at a designated enlarging / reducing ratio, and smoothing or edge-processing the digital image data according to the type of the image. An image processing method comprising a digital filter processing step of performing an emphasis filter processing, wherein any one of the enlargement / reduction processing step and the digital filter processing step is performed on the digital image data according to the designated enlargement / reduction ratio. An image processing method having a switching step of switching whether or not to execute first. 8. The image processing method according to claim 7, wherein said switching step includes a threshold value selecting step of selecting a different threshold value according to an image type of the input digital image data. A comparing step of comparing a scaling ratio with a threshold value selected in the threshold value selecting step, wherein when the scaling ratio is higher than the threshold value based on a comparison result by the comparing means, the digital filter Processing step, then in the order of the scaling processing step, if the scaling ratio is lower than the threshold, the scaling processing step;
Next, the processing order is switched so as to be executed in the order of the digital filter processing steps. 9. An enlargement / reduction processing step of performing an enlargement / reduction processing of an input digital image data at a designated enlargement / reduction ratio, and smoothing or edge processing of the digital image data according to the type of the image. A digital filter processing step of performing an emphasis filter processing, wherein when the image type of the digital image data is not a character image, the digital filter processing step is performed on the digital image data, and then the scaling processing is performed. While processing is performed in the order of steps, when the type of the image is a character image, according to the specified scaling ratio, the digital image data is subjected to either the scaling processing step or the digital filter processing step first. An image processing method, comprising: a switching control step of switching between execution and execution. 10. An image reading device comprising the image processing device according to claim 1. 11. A copying machine comprising the image processing device according to claim 1. 12. An enlargement / reduction processing unit for performing enlargement / reduction processing of an input digital image data at a designated enlargement / reduction ratio, and smoothing or edge processing of the digital image data according to the type of the image. A control program executed by a computer that controls an image processing apparatus including a digital filter processing unit that performs enhancement filter processing, the control method comprising: A computer-readable recording medium storing a control program having a switching procedure for switching which of a processing unit and a digital filter processing unit is executed first.