JP3154461B2 - Image processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and, more particularly, to an image processing apparatus for performing scaling of a digital image signal.

[0002]

2. Description of the Related Art It is well known that moire fringes occur in digital copying machines due to interference between the dot cycle of a halftone image and the sampling cycle of a digital image input device. Therefore, a smoothing process has been performed on the image signal.

[0003] In addition, sharpening processing has often been performed to correct the resolving power of image input devices and image output devices.

On the other hand, in image processing apparatuses such as digital copiers, scaling processing such as enlargement and reduction has been performed by interpolation or sampling of image data.

In the conventional image processing apparatus described above, when performing image processing by combining smoothing processing, sharpening processing, and scaling processing, the following tendencies are known.

(1) In the case of enlargement / magnification processing, particularly in the case of enlarging a smooth image such as a silver halide photographic image as an original, the image data is subjected to a sharpening processing and then a magnification processing is performed. The effect is greater for the sharpening process.

(2) In the case of reduction / magnification processing, in order to reduce moiré fringes, the period of a halftone dot image changes in accordance with the magnification, and therefore moiré is performed by performing smoothing processing on image data in advance. It is better to eliminate the periodicity of the halftone dots that cause fringes, and then reduce and sharpen them.

[0008]

However, in the above-described conventional image processing apparatus, for example, only one filter unit for performing the sharpening processing is provided in the apparatus, and the sharpening processing and the scaling processing are not performed. The processing order was fixed. Therefore,
It is difficult to change the order in which the sharpening process is performed between the time of enlargement and the time of reduction in the scaling process, and it has not been possible to output an optimal image at both the time of enlargement and the time of reduction.

[0009]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving the above-mentioned problems, and has the following structure as one means for solving the above-mentioned problems.

That is, an image input means for inputting an image signal, a scaling factor designating means for designating a scaling factor for scaling the image signal, and a first means for performing a spatial filtering process on the image signal input by the input means. Filter processing means, scaling means for scaling the image signal filtered by the first filter processing means in accordance with the scaling factor designated by the scaling factor designating means, and scaling by the scaling means. Second to apply spatial filtering to the image signal
And when the magnification / magnification is designated by the magnification / magnification designating means, the first filter processing means performs a sharpening process, and the second filter processing means performs a smoothing process. When the reduction / magnification is designated by the magnification / magnification designating means, the first filter processing means carries out a smoothing process and the second filter processing means carries out a sharpening process.

For example, there is provided storage means for storing at least two spatial filter coefficients, and the filter coefficient in the first spatial filter processing means is stored in the storage means in accordance with the scaling factor designated by the scaling factor designating means. A filter coefficient is selected and set, and a filter coefficient in the second spatial filter processing means is set by selecting a filter coefficient stored in the storage means in accordance with a magnification specified by the magnification specifying means. It is characterized by the following.

[0012]

And determining means for determining whether or not the image input by the image input means is a halftone image. When the determining means determines that the image is not a halftone image, the second means is used. The filter processing means does not perform the smoothing processing.

[0014]

With the above arrangement, a sharpening effect can be obtained in the case of enlargement in the scaling process, and moire fringes can be removed in the case of reduction.
Therefore, there is a specific operation and effect that the image quality of the output image can be improved in both enlargement and reduction.

[0015]

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

<First Embodiment> FIG. 1 is a sectional view showing the internal structure of a digital copying machine 100 according to a first embodiment of the present invention. In FIG. 1, reference numeral 100 denotes a digital copier main body, which reads an original image and forms an image on a recording paper as a recording medium.

Reference numeral 101 denotes a document feeder, 120 denotes a platen glass surface, 121 denotes a scanner, 122 denotes a lamp, and 123,
124 and 125 are mirrors, 126 is a lens and 127 is an image sensor. The document image is sent to the document feeder 101,
Alternatively, the light is radiated from the lamp 122 in the scanner 121 by being placed on the platen glass surface 120 by the operator and reflected in the document image, and the reflected light is reflected by mirrors 123 to 125
And is input to the image sensor 127 via the lens 126 and is converted into an electric signal. Then, the scanner 121 scans the entire surface of the original image to obtain image data of the original image.

Reference numeral 300 denotes various switches for operation and L
This is an operation panel on which an ED display and the like are arranged. Image data read by the image sensor 127 is processed by an image processing unit described later and converted into a video signal.

The laser driver 102 is a semiconductor laser 10
3 for driving the semiconductor laser on and off in accordance with an input video signal. The laser light 104 is swung right and left by a rotary polygon mirror 105 to scan on an electrostatic drum 106. Thus, an electrostatic latent image of a character pattern is formed on the electrostatic drum 106. This latent image is stored in a developing unit 107 around the electrostatic drum 106.
And then transferred to recording paper. Cut sheets are used for this recording paper, and cassette recording paper is LBP10
The paper feed roller 10 is accommodated in the paper cassette
9 and are fed into the apparatus by the conveying rollers 110 and 111 and supplied to the electrostatic drum 106.

Next, a detailed configuration of the digital copying machine 100 of the present embodiment is shown in a block diagram of FIG.

In FIG. 2, reference numeral 201 denotes an image input unit, which comprises an image reading unit 204 for reading a document image and a scaling ratio designation unit 205 on the operation panel 300 for designating a scaling ratio. Reference numeral 202 denotes an image processing unit that actually performs a scaling process on an image signal input from the image input unit 201. The CPU 2 controls the operation of the entire image processing apparatus according to the present embodiment.
09, a filter processing unit A206, a scaling processing unit 2
07, a filter processing unit B208, a memory A210 including a ROM and a RAM, a memory B211 and the like. Reference numeral 203 denotes an image output unit.
2, the actual output of the image subjected to the optimal processing is performed.

In this embodiment, the memory A210 stores spatial filter coefficients (edge enhancement coefficients) used for sharpening processing, and the memory B211 stores spatial filter coefficients (smoothing coefficients) used for smoothing processing. Are stored in accordance with the respective scaling factors. Image processing unit 202
The CPU 109 installed in the memory A 210 and the memory B 2 in accordance with the scaling factor designated by the scaling factor designating unit 205.
An appropriate coefficient is selected from each of 11 and set in the filter processing unit A206 or the filter processing unit B208.
At this time, the CPU 209 controls which coefficient is set to which filter depending on whether the process is the enlargement process or the reduction process. Therefore, in this embodiment, the impulse response characteristics of the filter processing unit A 206 and the filter processing unit B 208 change depending on the magnification.

The state of the scaling process in the image processing apparatus according to the present embodiment having the above-described configuration will be described below in detail with reference to the flowchart of FIG.

First, in step S300, the magnification is set by the operator at the magnification specifying section 205 of the image input section 201.
Is specified by Subsequently, in step S301, it is determined whether to perform the enlargement process, the reduction process, or not to perform the scaling process based on the designated scaling factor. Variable magnification is 100
Enlargement processing if larger than%, scaling processing if smaller than 10%
If it is 0%, it is assumed that the magnification is the same and no scaling process is performed.

In step S301, the scaling factor is 100
%, That is, if the enlargement process has been designated, the process proceeds to step S302. In step S302, the CPU 209 shown in FIG. 2 selects a sharpening spatial filter coefficient from the memory B211 in accordance with the scaling factor specified in step S300, and in step S303, sets the selected spatial filter coefficient in the filter processing unit A206. I do. Next, in step S304, the CPU 209 determines whether the
A spatial filter coefficient for smoothing is selected from 0 according to the scaling factor, and the spatial filter coefficient selected in step S305 is set in the filter processing unit B208.

With the above processing, the edge enhancement coefficient is set in the filter processing unit A206 and the smoothing coefficient is set in the filter processing unit B208 in the enlargement processing.

Subsequently, the process proceeds to step S314, where the image of the document is read by the image reading unit 204 of the image input unit 201 and subjected to predetermined color processing and the like, and then the process proceeds to step S315. In step S <b> 315, a known filtering process is performed on the input image signal by the filter processing unit A <b> 206, and the image signal is output to the scaling processing unit 207. Filter processing unit A2 by step S303
Since a filter coefficient for edge enhancement is set in 06, the filter processing in step S315 performs edge enhancement processing, that is, sharpening processing.

Then, the process proceeds to step S 316, in which the enlargement processing to the magnification specified in step S 300 is performed in the scaling processing section 207 by a known method, such as pixel complementation, and output to the filter processing section B 208. Is done.

Subsequently, in step S317, known filter processing is performed by the filter processing unit B208.
The image is output to the image output unit 203. Since a smoothing filter coefficient is set in the filter processing unit B208 in step S305, the filtering process in step S317 performs a smoothing process, that is, a smoothing process.

In step S318, the image output unit 203 outputs an enlarged image that has been optimally sharpened and smoothed.

As described above, the enlargement / reduction processing in this embodiment is performed. Next, the reduction / reduction processing will be described below.

In step S301 described above, if the scaling ratio is 100% or less, that is, if the reduction process is designated, the process proceeds to step S306. Step S306
In step S300, the CPU 209 shown in FIG. 2 selects a smoothing spatial filter coefficient from the memory A210 according to the scaling factor specified in step S300, and sets the selected spatial filter coefficient in the filter processing unit A in step S307. Next, in step S308, the CPU 209
A sharpening spatial filter coefficient is selected from step 211 according to the scaling factor, and the spatial filter coefficient selected in step S309 is set in the filter processing unit B.

By the above processing, in the reduction processing, the smoothing coefficient is set to the filter processing unit A206, and the edge enhancement coefficient is set to the filter processing unit B208.

Subsequently, the process proceeds to step S314, where the original image is read in step S314 as in the case of the above-described enlargement process, and in step S315, the filter processing unit A206 applies a known process to the input image signal. , And output to the scaling unit 207. By the step S307, the filter processing unit A2
Since a smoothing filter coefficient is set in 06, the filtering process in step S315 performs a smoothing process, that is, a smoothing process.

Then, the process proceeds to step S316, in which the scaling unit 207 performs reduction processing to the scaling ratio designated in step S300 by a known method such as pixel sampling, and outputs the result to the filter processing unit B208. Is done.

Subsequently, in step S317, known filter processing is performed by the filter processing unit B208.
The image is output to the image output unit 203. Since a filter coefficient for edge enhancement has been set in the filter processing unit B208 in step S309, the filter processing in step S317 performs edge enhancement processing, that is, sharpening processing.

Then, in step S318, the image output unit 203 outputs a reduced image that has been optimally sharpened and smoothed.

As described above, the reduction / magnification processing in this embodiment is performed.

Further, in the present embodiment, step S300
When the setting of the scaling factor in step is 100%, no scaling process is performed as the equal-size process.

In the present embodiment, in the case of the same-magnification processing, if it is determined in step S301 that the magnification is 100%, that is, the magnification is equal, the process proceeds to step S310. Then, in step S310, the CPU 209 shown in FIG. 2 selects a sharpening spatial filter coefficient from the memory B211 according to the scaling factor specified in step S300, and in step S311, the selected spatial filter coefficient is filtered by the filter processing unit A. Set to. Next, in step S312, C
The PU 209 selects a spatial filter coefficient for smoothing from the memory A210 according to the scaling factor, and sets the spatial filter coefficient selected in step S313 in the filter processing unit B.

Through the above processing, the edge enhancement coefficient is set in the filter processing unit A206 and the smoothing coefficient is set in the filter processing unit B208 in the enlargement processing.

The subsequent processing is the same as the above-described enlargement / reduction processing, and a detailed description thereof will be omitted. However, the magnification process in step S316 is not particularly performed in the case of the equal magnification process.

In the same magnification processing, the coefficient set in the filter processing unit A in step S311 has been described as an edge emphasis coefficient, and the coefficient set in the filter processing unit B in step S313 has been described as a smoothing coefficient. May be reversed.

As described above, the image processing apparatus according to the present embodiment performs the scaling process and the equal-size process.

In this embodiment, the case where the edge emphasis coefficient is stored in the memory A210 and the smoothing coefficient is stored in the memory B211 according to each scaling factor has been described, but the present embodiment is not limited to this. Instead, the edge enhancement coefficient may be stored in the memory B211 and the smoothing coefficient may be stored in the memory A210.
6 and the filter unit B207 may determine the spatial filter coefficient to be set.

As described above, according to the present embodiment, a sharpening process is performed in the first stage of the scaling process and a smoothing process is performed in the second stage to form a high-quality enlarged image in which the sharpening effect is further enhanced. Further, by performing a smoothing process at a stage before the scaling process and a sharpening process at a stage after the scaling process, it is possible to form a high-quality reduced image from which moiré fringes have been removed.

<Second Embodiment> As a second embodiment according to the present invention, in addition to the processing of the above-described first embodiment, an example in which a pre-scan of a document image is performed before designating a scaling factor will be described below. I do.

The configuration of the image processing apparatus according to the second embodiment can be realized by the same configuration as the first embodiment shown in FIGS. 1 and 2 described above.

FIG. 4 is a flowchart showing the scaling process of the second embodiment.

First, in step S401, prescanning is performed before the image reading section 204 shown in FIG. 2 actually reads the original image. And step S
At 402, it is determined whether the original image is a halftone image or a silver halide photograph. If it is determined in step S402 that the document image is a halftone image, moire fringes due to the dot cycle of the halftone image are likely to occur.
Proceeding to step 403, a halftone image scaling process is executed. This halftone image scaling process is the same process as the first embodiment shown in FIG. 3 described above. That is, both the sharpening process and the smoothing process are unconditionally performed on the document image.

On the other hand, if it is determined in step S402 that the original image is a smooth image such as a silver halide photograph,
Since the occurrence of moiré fringes is unlikely to occur, the necessity of performing a smoothing process is relatively small, and therefore, the process is not performed in step S40.
Then, the program proceeds to step 4 to execute a silver halide photograph scaling process. FIG. 5 shows the details of the silver halide photograph magnification change processing in step S404.

In FIG. 5, the same processes as those of the halftone image scaling process shown in FIG. 3 are denoted by the same reference numerals as in FIG. 3, and the detailed description will be omitted.

In the scaling process for silver halide photography in FIG. 5, the enlargement process in the scaling process for the halftone image shown in FIG. 3 and the smoothing process in the same-size process are omitted. That is,
The processing of selecting the smoothing coefficient in steps S304 and S312 in FIG. 3 and the processing of storing the data in the filter processing unit B208 in steps S305 and S313 are omitted.

That is, in the case of the enlargement and equal magnification processing, the smoothing processing is not performed. In the case of the enlargement and equal magnification processing in FIG. 5, the filter processing in the filter processing unit B in step S317 is performed. Is not performed. However, in the equal magnification processing, the storage of the edge enhancement coefficient in the filter processing unit A206 in step S311 may be stored in the filter processing unit B208. in this case,
Filter processing in the filter processing unit A206 in step S315 becomes invalid.

In the second embodiment, instead of the pre-scan processing shown in step S401 in FIG. 4, for example, an operation panel 300 shown in FIG. 1 of the printer body is used to determine whether or not the original is a halftone image. It is also possible to make a determination by having the user input.

As described above, according to the second embodiment,
Since the number of steps in the enlargement and equal-magnification processing is smaller than in the case of the above-described first embodiment, the effect of improving the processing speed while maximizing the effect of sharpening can be obtained. In the case of reduction processing, the same effect as in the first embodiment can be obtained.

In the first and second embodiments described above, an example of a copying machine using a laser beam printer as a printer has been described. However, the present invention is not limited to this. The present invention is applicable to all apparatuses that perform scaling processing of an image signal, such as a copier using a jet printer or an ink jet printer, and a facsimile apparatus.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus.

[0059]

As described above, according to the present invention, a sharpening effect can be obtained in the case of enlargement in the scaling process, and a moire fringe can be removed in the case of reduction. Therefore, it is possible to improve the image quality of the output image in both enlargement and reduction.

[0060]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a cross section of an image processing apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a detailed configuration of an image processing unit according to the embodiment.

FIG. 3 is a flowchart illustrating a scaling process according to the embodiment.

FIG. 4 is a flowchart showing a prescan process in a second embodiment according to the present invention.

FIG. 5 is a flowchart illustrating a scaling process according to the second embodiment.

[Explanation of symbols]

 201 image input unit 202 image processing unit 203 image output unit 204 image reading unit 205 scaling unit 206 filtering unit A 207 scaling unit 208 filter unit B 209 CPU 210 memory A 211 memory B

Claims (4)

(57) [Claims] An image input unit for inputting an image signal; a scaling factor designating unit for designating a scaling factor for scaling the image signal; and a first unit for performing a spatial filtering process on the image signal input by the input unit. Filter processing means; scaling means for scaling the image signal filtered by the first filter processing means in accordance with a scaling factor designated by the scaling factor designating means; Second filtering processing means for performing a spatial filtering process on the image signal obtained, and when the magnification / magnification is specified by the magnification / magnification specifying means,
The first filter processing means performs a sharpening process on the second
The filter processing means performs smoothing processing respectively, and when reduction / magnification is designated by the magnification / magnification designation means,
The first filter processing means performs a smoothing process on the second
An image processing apparatus, wherein the filter processing means performs sharpening processing. 2. A storage means for storing at least two spatial filter coefficients, wherein the filter coefficients in the first filter processing means are:
2. The image processing apparatus according to claim 1, wherein a filter coefficient stored in said storage means is selected and set according to a scaling factor designated by said scaling factor designating means. 3. A filter coefficient in said second filter processing means, wherein a filter coefficient stored in said storage means is selected and set according to a scaling factor designated by said scaling factor designating means. The image processing apparatus according to claim 2. 4. An image processing apparatus comprising: a determination unit configured to determine whether an image input by the image input unit is a halftone image; and if the determination unit determines that the image is not a halftone image,
2. The image processing apparatus according to claim 1, wherein the second filter processing unit does not perform a smoothing process.