JP2003274180A - Image processor, image processing method, printer driver, computer readable storage medium and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate the noise that occurs in a luminance signal and a color- difference signal without blurring an image contour part. <P>SOLUTION: A contour determining part 1302 determines the contour part on an image, a luminance enhancing 1303 enhances the contour part in a luminance signal, and a luminance smoothing part 1303 smoothes parts other than the contour to eliminate the noise in the luminance signal. A color noise determining part 1304 determines a color noise part independently of the contour part of the image, and a color noise smoothing part 1305 smoothes a color- difference signal for pixels of the color noise part in accordance with the occurrence situation of the color noise to eliminate the color noise. By performing these processing, luminance noise or color noise in the image can be eliminated without deteriorating the original image. <P>COPYRIGHT: (C)2003,JPO

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 method, a printer driver, a computer-readable storage medium and a computer program, and is particularly suitable for removing luminance noise or color noise. is there.

[0002]

2. Description of the Related Art In recent years, with the development of hard copy technology, in particular, full-color hard copy technology, a high fidelity image is reproduced by using an advanced printing technology such as an ink jet recording method and a high pixel digital camera. Is becoming possible.

In terms of color reproducibility, it has been advanced to the extent that it is said to have a reproducibility equivalent to that of a silver salt photograph due to recording materials and image processing. However, the image itself to be printed may include luminance noise or color noise due to the characteristics of the image sensor or the like in the input device. For example, noise due to the dark current of the CCD element, fixed pattern noise, noise generated in the signal line for color signal transmission, etc. may be mixed in the input image.

To solve this problem, there is generally known a method of smoothing an image signal to remove noise generated in the image. As an example, patent 2790604
In the image, the image data is classified into a contour portion, a noise portion, and a non-contour portion. The contour portion is subjected to contour emphasis set according to the ratio of the contour region, and the noise portion is classified into
By performing noise removal processing, other noise portions are removed while maintaining the contour of the image.

On the other hand, in Japanese Patent Laid-Open No. 05-183924,
The image is divided into a plurality of regions from the contour extraction, a filter size larger than the noise period of the luminance signal and the color difference signal is set in the region other than the contour, and the averaging process is performed while moving pixel by pixel. By doing so, the luminance noise and the color noise of the portion other than the contour are removed.

[0006]

However, the color noise due to the characteristics of the input device is generated in the entire image regardless of the contour in the image. In the conventional method, the color noise removal processing is performed in the area other than the contour. However, the color noise on the contour cannot be removed by just performing the above, and an unnatural image may be obtained even after the correction. Furthermore, in Japanese Patent Laid-Open No. 05-183924,
When the area other than the contour is smaller than the noise cycle, it may not be possible to remove noise only in that area. That is, it is necessary to remove the color noise generated in the entire image without being restricted by the outline of the image.

On the other hand, even if the contour is extracted using a conventionally known Laplacian filter or the like, the contour of the image cannot be completely extracted. That is, the necessary contour may not be extracted or an unnecessary isolated point may occur. Therefore, the contour extraction in the noise removal processing has a problem that it is necessary to remove the isolated points after the contour extraction processing.

The present invention has been made in consideration of the above-mentioned problems, and does not blur the outline portion of an image,
An object of the present invention is to enable removal of luminance noise and color noise generated in the luminance signal and the color difference signal.

[0009]

An image processing apparatus according to the present invention classifies image data into a contour portion and a non-contour portion, and with respect to noise generated in a signal representing brightness which constitutes the image data, The noise removal processing is performed on the non-contour portion, and the noise removal processing is performed according to the generation status of the noise generated in the color signal with respect to the noise generated in the signal representing the tint forming the image data. It is characterized by giving.

Another feature of the image processing apparatus of the present invention is that in an image processing apparatus for removing noise generated in an image, contour extraction filter processing is performed on the signal representing the brightness of the image. A contour extracting means for extracting a contour of the image by means of a first smoothing means for performing a smoothing process on the signal representing the brightness of the portion other than the contour extracted by the contour extracting means; Based on the color noise determination means for performing color noise determination and the color noise determination determined by the color noise determination means, it is checked whether or not the pixel of interest is the color noise portion generated in the signal representing the tint. It is characterized in that it has a color noise detecting means and a second smoothing means for performing a smoothing process on a signal representing the tint of the color noise portion detected by the color noise detecting means.

Another feature of the image processing apparatus of the present invention is that the brightness signal is a luminance signal and the tint signal is a color difference signal.

Another feature of the image processing apparatus of the present invention is that the signal representing the brightness is subjected to smoothing processing depending on the generation state of the color noise portion detected by the color noise detecting means. Is characterized by.

Another feature of the image processing apparatus of the present invention is that the selection process of the portion to which the signal representing the tint is subjected to the smoothing process is performed on the image obtained from the signal representing the brightness. It is characterized by being independent of the contour part.

Another feature of the image processing apparatus of the present invention is that when an isolated point is generated in the contour extracting means, the remaining portion from which the isolated point is removed is extracted as a contour. It has a feature.

Another feature of the image processing apparatus of the present invention is that the contour extracting means for the signal representing the brightness uses a Laplacian filter process or a high pass filter process.

Another feature of the image processing apparatus of the present invention is that the color noise determining means obtains the difference between the signals representing the tint of the pixel of interest and its neighboring pixels, and the result of the difference is obtained. It is characterized in that whether or not the pixel of interest is a color noise portion is determined by performing threshold value determination on the other hand.

Another feature of the image processing apparatus of the present invention is that it has an emphasizing means for emphasizing a signal representing brightness in the contour portion extracted by the contour extracting means. It has a feature.

Another feature of the image processing apparatus of the present invention is that in the contour extracting means, the first smoothing means, and the second smoothing means, the brightness depends on the image to be corrected. Is provided with a filter selection means for selecting a filter for performing a filtering process on the signal indicating

Another feature of the image processing apparatus of the present invention is that the contour extracting means, the first smoothing means, the second smoothing means, and the emphasizing means, depending on the image to be corrected. It is characterized in that it has a filter selecting means for selecting a filter from a plurality of filters for performing a filtering process applied to the signal representing the brightness.

The printer driver of the present invention is characterized by using the image processing apparatus described above.

According to the image processing method of the present invention, the image data is classified into a contour portion and a non-contour portion, and noise generated in the signal representing the brightness forming the image data is classified into the non-contour portion. In addition to the noise removal processing, the noise removal processing is performed on the noise generated in the signal representing the tint forming the image data according to the generation status of the noise generated in the color signal. .

Another feature of the image processing method of the present invention is that in the image processing method for removing noise generated in an image, contour extraction filter processing is performed on the signal representing the brightness of the image. A contour extraction process for extracting the contour of the image by means of a first smoothing process for performing a smoothing process on a signal representing the brightness of a portion other than the contour extracted by the contour extraction process; Based on the color noise determination processing for performing color noise determination and the color noise determination determined by the color noise determination processing, it is determined whether or not the pixel of interest is the color noise portion generated in the signal representing the tint. It is characterized in that it has a color noise detection process and a second smoothing process for performing a smoothing process on a signal representing a tint of the color noise portion detected by the color noise detection process.

Another feature of the image processing method of the present invention is that the signal representing the brightness is a luminance signal and the signal representing the tint is a color difference signal.

Another feature of the image processing method of the present invention is that the signal representing the brightness is subjected to smoothing processing depending on the generation state of the color noise portion detected by the color noise detection processing. Is characterized by.

Another feature of the image processing method of the present invention is that the selection process of the portion to which the signal representing the tint is subjected to the smoothing process is performed on the image obtained from the signal representing the brightness. It is characterized by being independent of the contour part.

Another feature of the image processing method of the present invention is that when an isolated point is generated in the contour extraction processing, the remaining part from which the isolated point is removed is extracted as a contour. It has a feature.

Another feature of the image processing method of the present invention is that the contour extraction process for the signal representing the brightness uses a Laplacian filter process or a high-pass filter process.

Another feature of the image processing method of the present invention is that in the color noise determination processing, the difference between the signals representing the tint of the pixel of interest and its neighboring pixels is obtained, and the result of the difference is obtained. It is characterized in that whether or not the pixel of interest is a color noise portion is determined by performing threshold value determination on the other hand.

Another feature of the image processing method of the present invention is that the signal representing the brightness is enhanced in the contour portion extracted by the contour extraction processing.

Another feature of the image processing method of the present invention is that in the contour extraction processing, the first smoothing processing, and the second smoothing processing, the brightness according to the image to be corrected is changed. It is characterized by having a filter selection process for selecting a filter from among a plurality of filters for performing the filtering process applied to the signal indicating.

Another feature of the image processing method of the present invention is that the contour extraction process, the first smoothing process, the second smoothing process, and the emphasizing process depend on the image to be corrected. It is characterized in that it has a filter selection process for selecting a filter for performing a filter process to be applied to the signal representing the brightness from a plurality of filters.

The storage medium of the present invention is a recording medium in which a computer-readable program is stored, which performs contour extraction processing on luminance signals and smoothes luminance signals and color difference signals in portions other than the contours. Therefore, a program for correcting the image data is stored.

Another feature of the storage medium of the present invention is that a program for causing a computer to function as each of the above means is recorded.

Another feature of the storage medium of the present invention is that a program for causing a computer to execute the image processing method described above is recorded.

The computer program of the present invention is characterized by causing a computer to execute the above-described image processing method.

Since the present invention has the above technical means, the smoothing process is performed on the luminance signal of the portion other than the extracted contour by the contour extracting process performed on the luminance signal. Further, it is possible to perform the smoothing process using the optimum filter on the color difference signal determined to be the color noise portion based on the color noise determination regardless of whether it is the contour portion.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of an image processing apparatus, an image processing method, a printer driver, a computer-readable storage medium and a computer program of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of an image processing apparatus according to the present invention and showing an example in which an image processing system is configured using the image processing apparatus. In FIG. 1, a printer 106 such as an inkjet printer and a monitor 105 for displaying an image are connected to the host computer 100.

The host computer 100 is a word processor,
Spreadsheet, application software 101 such as an internet browser, an OS (Operating # System) 102, and various drawing command groups (image drawing commands, which show output images issued to the operating system 102 by the application software 101). A printer driver 103 for processing a text drawing command and a graphics drawing command to create print data, and application software 101
Has a monitor driver 104 as software for processing various drawing commands issued by the computer and displaying them on the monitor 105.

Further, the host computer 100 is a central processing unit CPU 108, a hard disk driver HD 107, a random access memory (RAM) 10 as various kinds of hardware capable of operating these software.
9, a read only memory (ROM) 110 and the like.

In the embodiment shown in FIG. 1, for example, a Windows (R) 95 of Microsoft Corporation is used as an OS in a personal computer of an AT compatible machine of IBM Corporation which is widely used.
It is conceivable as one embodiment that the monitor 105 and the printer 106 are connected to each other by installing any printable application.

In the host computer 100, the monitor 1
On the basis of the display image displayed on 05, the application software 101 classifies the text data into texts such as characters, the graphics data into graphics such as figures, and the image image data into natural images. Create output image data using

When the output image data is printed out, the application software 101 issues a print output request to the operating system 102, and the graphics data portion is composed of a graphics drawing command and the image image data portion is composed of an image drawing command. A drawing command group indicating an output image to be issued to the operating system 102.

Next, the operating system 102
Receives the output request of the application software 101, and the printer driver 103 corresponding to the output printer.
Issue a drawing command group to. The printer driver 103 is
The print request and the drawing command group input from the operating system 102 are processed, print data printable by the printer 105 is created, and the print data is transferred to the printer 105.

When the printer 105 is a raster printer, the printer driver 103 sequentially performs image correction processing in response to a drawing command from the operating system 102. Then, after sequentially rasterizing to the RGB 24-bit page memory and rasterizing all drawing commands, the contents of the RGB 24-bit page memory are converted into a data format printable by the printer 105, for example, CMYK data, and transferred to the printer 105.

Next, the processing performed by the printer driver 103 will be described with reference to the block diagram of FIG. The image correction processing unit 120 uses the operating system 10
For the color information included in the drawing command group input from 2,
Perform image correction processing. In the image correction processing performed by the image correction processing unit 120, color noise removal processing is performed based on RGB color information.

The printer correction processing unit 121 first rasterizes the drawing command based on the color information subjected to the image correction processing by the image correction processing unit 120, and generates a raster image on the RGB 24-bit page memory. Then, for each pixel, CMYK data depending on the color reproducibility of the printer is generated and transferred to the printer 105.

Next, with reference to the flow chart shown in FIG. 4, the procedure relating to the luminance noise or chrominance noise removal processing performed in the image correction processing unit 120 will be described. In addition,
The conversion situation of the image signal in the noise removal processing is shown in FIG. In FIG. 3, reference numeral 31 is a Y / C separation circuit for converting the three-color primary color signals into luminance and color difference signals, 32 is a luminance signal enhancement / smoothing section, 33 and 34 are color difference signal smoothing sections, and 35
Is a circuit for demodulating the Y / C separated signal into three primary color signals.

The luminance noise or color noise removal processing is performed on the image image data portion relating to the same image indicated by the image drawing command. Therefore, for example, when the output image includes the graphics image and the image image, the image image portion related to the same image is extracted and the luminance noise or color noise removal processing is performed.

By the way, the most general and highly practical method for removing noise from an image in which noise has occurred is to perform smoothing on the image signal. However, if the entire image is uniformly smoothed, the contour portion in the image is also blurred. Therefore, it is necessary to first perform the contour extraction using the luminance signal in which the contour in the image most often appears.

Then, smoothing processing is performed on the area other than the contour. This is to remove the luminance noise generated in the luminance signal, and for example, the luminance signal in a visually flat portion such as the sky, the wall of a building, or the surface of a face can be leveled cleanly.

By the way, the luminance noise and the color noise are
It occurs on the entire image regardless of the contour. However, the color difference signal is less likely to represent the contour in the image than the luminance signal. Therefore, in the case of the luminance signal, the smoothing process is performed only on the portion other than the contour, but the color noise generated in the color difference signal may be removed regardless of whether it is the contour portion.

Therefore, in addition to the contour extraction by the luminance signal, it is checked whether or not the target pixel is a color noise occurrence portion, and even if the target pixel is the contour portion obtained from the luminance signal, if there is color noise, the color difference signal is detected. Is smoothed, and
If it is not a color noise portion or is a color boundary portion (a portion having a difference greater than the color difference between color noises, such as skin color and sky blue), the color difference signal is not processed. By doing so, it is possible to remove only the color noise without visually blurring the outline of the image.

By the way, when the smoothing process is performed on the luminance signal and the color difference signal, even if the contour portion is held, the entire image looks rather blurred to some extent. Therefore, it is necessary to perform emphasis processing on the pixels determined to be the contour portion from the luminance signal.

By doing so, the contour of the image can be held or emphasized, the noise of the luminance and the color difference signal can be completely removed, and the image can be corrected without any adverse effect on appearance. In the following description, the luminance noise or color noise removal processing including the contour determination and the like will be described in more detail.

First, the three primary color signals forming an image are converted into a luminance signal and a color difference signal. This process
The Y / C separation unit 1306 shown in the functional block diagram of FIG.
Done in.

(Contour Extraction Processing) In the contour extraction processing of step S01, the contour of the luminance signal Y is extracted using, for example, a filter as shown in FIG. 5, and the extracted value D_Y is held. That is, D_Y (i, j) =-Y (i-1, j-1) + Y (i-1, j) -Y (i-1, j + 1) + Y (i, j-1) + Y (i, j + 1) ) -Y (i + 1, j-1) + Y (i + 1, j) -Y (i + 1, j + 1) +255 (Equation 1).

Here, the extracted value D_Y can be used in the contour determination processing and the contour emphasis processing which are the subsequent steps. Further, when contour enhancement or smoothing is not performed, or when a high-speed unit dedicated to contour enhancement or smoothing is available, the value D_Y obtained here may be discarded at the same time when the contour determination is completed.

In the present embodiment, the filter shown in FIG. 5 is used. However, in order to extract the contour, a Laplacian filter or a pass component of a high-pass filter in the spatial frequency domain is used,
The same effect can be obtained by using a difference value in the real time domain, assuming a moving image. This processing is performed by the edge extraction unit 1301 shown in the functional block diagram of FIG.

(Contour Judgment Processing) Next, in the contour judgment processing of step S02, the value D held in the above-mentioned contour extraction processing.
_Y is compared with a threshold Th for contour determination to determine the contour. In this embodiment, the area less than the threshold Th is the contour portion, and the area greater than the threshold Th is the portion other than the contour.

The threshold value Th may be set using a predetermined fixed value, or may be set for each processing target image by analyzing the histogram of the input image. In this case,
A histogram calculation / analysis unit is required. In addition, information on image resolution and input device characteristics can be obtained from image data,
It may be variably set based on it. This process
Edge determination unit 1302 shown in the functional block diagram of FIG.
Done in.

If the pixel of interest (i, j) is determined to be the contour portion as a result of the contour judgment processing, step S
03, the outline enhancement processing is performed. Note that this step may be omitted if it is premised that the edge enhancement processing is performed, or if deterioration of the apparent resolution of the edge regarding luminance is not a problem. On the other hand, if the result of determination in step S02 is that it is a portion other than the contour, processing proceeds to the luminance smoothing processing in step S03 '.

Here, if the contour extraction filter is applied only once, an unintended portion in the image may be determined as a contour. For example, even if the pixel of interest is determined to be the contour, if the number of pixels that are determined to be the contour among the pixels adjacent thereto is small, the pixel of interest becomes an isolated point. In such a case, if a process of removing the isolated point from the contour portion is added, the contour can be extracted with higher accuracy.

In the process after (luminance enhancement processing), color noise signal smoothing processing is applied to the color noise portion regardless of the contour. As a result, the image becomes visually unclear, so it is necessary to add emphasis processing to the contour portion extracted by the luminance signal. In the edge enhancement processing in step S03, edge enhancement is performed by adding an enhancement filter as shown in FIG. 6 to the luminance signal value Y (i, j).

That is, Y '(i, j) = 5 * Y (i, j) -Y (i-1, j) -Y (i + 1, j)                 -Y (i, j-1) -Y (i, j + 1) ... (Equation 2) Is performed.

After the color noise removal processing, or by performing the edge enhancement together with the color noise removal processing, the edge enhancement can be performed without enhancing the color noise.

Here, the data obtained for the contour determination is used to enhance the contour by speeding up and simplifying the processing. However, the contour enhancing processing is performed at another place in FIG. May be. For example, contour enhancement, then contour extraction,
The accuracy of the determination can be improved by performing the contour determination. Also, the same edge enhancement effect can be obtained by performing edge enhancement after removing color noise. It is also possible to use other processing having a contour enhancement effect, such as processing in the frequency domain.

If contour enhancement has already been performed on the input device side, contour enhancement need not be performed in this step. Further, with respect to the contour region of one pixel or more including the target pixel, the data of the original image may be passed through without performing the contour enhancement. In this case, the original image can be faithfully reproduced in the image area other than the color noise area. The brightness enhancement processing is performed by the brightness enhancement unit 1303 shown in the functional block diagram of FIG.

(Brightness Smoothing Processing) In step S03 ', the brightness signal is smoothed for the portion determined to be a portion other than the contour in step S02. By using the smoothing filter as shown in FIG. 7, the brightness can be easily blurred.

That is, Y '(i, j) = {8 * Y (i, j) + Y (i-1, j-1)                   + Y (i-1, j) + Y (i-1, j + 1)                   + Y (i, j-1) + Y (i, j + 1)                   + Y (i + 1, j-1) + Y (i + 1, j)                   + Y (i + 1, j + 1)} / 16 (Equation 3) Becomes

In this step as well as the contour enhancement processing, if contour smoothing processing has already been performed on the input device side,
This step may not be performed. In the present embodiment, one filter is used for smoothing the area other than the contour, but the filter may be variable according to the spatial frequency, or the filter may be applied only to a portion that meets a certain determination condition for the luminance signal. You may make a call. This process
The brightness smoothing unit 1303 ′ shown in the functional block diagram of FIG.
Done in.

(Color Noise Judgment Processing) In the color noise judgment processing, noise of the color difference signal which cannot be detected from the change of the luminance signal Y is detected. An image captured by a digital camera or a scanner may have color noise of a red, blue, or green spot pattern due to a CCD or the like.

The generation cycle and color difference of the color noise depend on the characteristics of the input device. For example, consider a case where the color noise period is 6 pixels. In step S04, the color-difference signals (Cr (i, j), Cb (i, j)) of the pixel of interest and the color-difference signal (Cr of the pixel located three places to the left (half the color noise period) from the pixel of interest (Cr (I-3, j), Cb (i-3,
j)) is within a certain range, that is, Th_C1 <| Cr (i, j) -Cr (i, j-3) | <Th_C2 and Th_C3 <| Cb (i, j) -Cb. If (i, j−3) | <Th_C4 (Equation 4), it is determined that color noise has occurred in the color difference signal of the pixel of interest (see FIG. 8). Then, step S04
If it is determined that the color noise is generated, the process proceeds to the color noise smoothing process of step S06.

On the other hand, as a result of the determination in step S04, if the color noise determination conditions are not met from the color difference signals for the three pixels to the left of the target pixel, the process proceeds to step S05, this time from the target pixel to the right 3 Pixel color difference signals (Cr (i + 3, j), Cb (i + 3,3)
j)) is within a certain range as above, that is, Th_C1 <| Cr (i, j) -Cr (i, j + 3) | <Th_C2 and Th_C3 <| Cb (i, j)- When Cb (i, j + 3) | <Th_C4 (Equation 5), it is determined that the pixel of interest has color noise (see FIG. 9). Then, as a result of the determination in step S05, if it is determined that the color noise is generated, step S07
Then, the process proceeds to (4) to smooth the color difference signal.

Finally, from both the left and right three pixels,
When it is determined that the pixel of interest does not have color noise (see FIG. 10), the color noise smoothing process is not performed on the pixel of interest. That is, when the color difference signal of the pixel of interest does not differ much from the color difference signals of the neighboring pixels, it is assumed that the hue is flat and there is no noise. On the other hand, when the difference from the color difference signal of the neighboring pixel is large, that portion is assumed to be a contour in terms of color and smoothing processing is not performed.

In the present embodiment, the threshold value Th_Cx is fixed, but it is also possible to extract the feature amount such as the histogram of the input image and set it based on this. Further, if the characteristics of the input device are known, it may be variably set accordingly. Further, this time, the color noise determination is performed using three neighboring pixels on the left and right, but a pixel adjacent to the pixel of interest may be used depending on the image to be corrected, or three or more distant pixels may be used. May be. The same result can be obtained by using upper and lower neighboring pixels.

As described above, by performing the color noise determination at most twice, it is possible to extract noise with high accuracy. The color noise determination process may be omitted when the image after the color noise removal process is subjected to the smoothing process for the entire color difference signal. The color noise determination process is performed by the color noise determination unit 1304 shown in the functional block diagram of FIG.

(Color Noise Smoothing Processing) In the color noise smoothing processing of steps S06 and S07, step S0
As in the case where the luminance signal Y is smoothed in 3 ′,
The color difference signal is smoothed using a smoothing filter. Here, it should be noted that the filter to be used is switched according to the color noise determination processing.

For example, in the color noise determination process of step S06, when the color difference signals of the three pixels on the left are used for comparison with the target pixel, the process is performed by the smoothing filter as shown in FIG. 11 ( Step S06). On the other hand, when the color noise is not determined from the three pixels on the left side and the color noise is determined from the three pixels on the right side in the color noise determination process of step S07, smoothing as shown in FIG. 12 is performed. Processing is performed using the digitizing filter (step S07).

In other words, by checking the occurrence status of color noise based on the color noise judgment and switching the color difference signal smoothing processing accordingly, only the color noise portion is blurred without blurring the color difference signal other than the color noise. Can be smoothed.

This method does not have the adverse effect of blurring an important part in the image as compared with the case where the color difference signals are uniformly smoothed over the entire image. Further, color noise on the contour can be completely removed as compared with the case where this processing is performed only on the contour area extracted from the luminance signal. This processing is performed by the color noise smoothing unit 1305 shown in the functional block diagram of FIG.

In this embodiment, NTSC YCrCb is used.
Although a signal is used, a G signal of an RGB signal is used instead of the luminance signal, and Cr ′ = R / (R
+ G + B), Cb '= B / (R + G + B), etc. can be used.

Further, the above color noise removal processing is performed by L * a * b.
The same effect can be obtained by using a coordinate system such as * or Yxy. Similar processing may be performed for a cylindrical coordinate system such as L * c * h *, HLS, etc. In such a case, processing for converting the coordinate value in the cylindrical coordinate system into rectangular coordinates is performed. After that, smoothing processing may be performed. Further, when only the color distortion needs to be corrected, the smoothing process may be performed on the change in the hue angle.
Similarly, the smoothing process for saturation has a similar effect.

The filter has a size of “5 × 5” or “3 × 5”.
The size is not limited to 3 "size and subject to vertical and horizontal directions, and similar effects can be obtained as long as they have low-pass characteristics. Of course, using a median filter has a similar effect.

Further, by appropriately changing the filter size according to the image to be corrected, it is possible to obtain a stable processing result regardless of the image resolution. Furthermore, a greater effect can be obtained by changing the filter coefficient according to the characteristics of the input device.

In the real space, the real time domain, and the spatial frequency domain, the same effect as that of the present invention can be obtained by performing the processing for removing the high frequency component from the signals other than the luminance signal Y. Regarding the signals except the luminance signal Y,
Processing for removing high frequency components is included in the scope of the present invention.

In this way, by performing noise removal processing on the luminance signal and the color difference signal by another method, it is possible to perform complete processing according to the noise characteristics while maintaining the contour of the image.

(Other Embodiments of the Present Invention) The present invention is applied to an apparatus or system connected to various devices so as to operate the various devices so as to realize the functions of the above-described embodiments. The program code itself for realizing the above and a means for supplying the program code to a computer, for example, a storage medium storing the program code constitutes the present invention.

As a storage medium for storing the program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM,
A magnetic tape, a non-volatile memory card, a ROM or the like can be used.

Further, not only the functions of the above-described embodiments are realized by the computer executing the supplied program code, but also the OS (operating system) in which the program code is operating in the computer, or It goes without saying that the program code also in the case where the functions of the above-described embodiment are realized in cooperation with other application software or the like is included in the embodiment of the present invention.

Further, the supplied program code is stored in the memory provided in the function expansion board of the computer or the function expansion unit connected to the computer, and then the function expansion board or function storage unit is instructed based on the instruction of the program code. Needless to say, the present invention also includes a case where the CPU or the like included in the above performs a part or all of the actual processing and the functions of the above-described embodiments are realized by the processing. Further, the plurality of embodiments may be combined.

[0092]

As described above, according to the present invention,
The image data is classified into a contour portion and a non-contour portion, and noise generated in the signal representing the brightness forming the image data is subjected to noise removal processing on the non-contour portion and the image data is With respect to the noise generated in the signal representing the tint, the noise removal processing is performed in accordance with the occurrence status of the noise generated in the color signal. Therefore, the luminance noise or the color noise generated in the image, It can be removed without degrading the original image.

According to another feature of the present invention, contour extraction processing is performed on the luminance signal, smoothing processing is performed on the luminance signal of the portion other than the contour, and it is defined based on the color noise judgment. Since the smoothing process is performed on the color difference signal in the color noise portion, the luminance noise or the color noise generated in the image can be removed without degrading the original image.

Further, according to another feature of the present invention, since the processing for the luminance signal and the processing for the color difference signal are performed independently, it is possible to remove the color noise in the contour portion of the image. Thereby, the image quality of the image can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an entire system.

FIG. 2 is a block diagram illustrating a schematic configuration of a printer driver.

FIG. 3 is a block diagram illustrating a circuit that converts an image signal in a luminance noise and color noise removal process.

FIG. 4 is a flowchart illustrating a procedure of noise removal processing.

FIG. 5 is a diagram showing an example of a contour extraction filter.

FIG. 6 is a diagram showing an example of an emphasis filter.

FIG. 7 is a diagram showing an example of a smoothing filter.

FIG. 8 is a diagram showing a case in which it is determined that there is color noise in a pixel of interest from three pixels to the left of the pixel of interest.

FIG. 9 is a diagram showing a case where it is determined that there is color noise in a pixel of interest from three pixels to the right of the pixel of interest.

FIG. 10 is a diagram showing a case where it is determined that the pixel of interest has no color noise.

FIG. 11 is a diagram showing an example of a filter for performing color noise smoothing processing in FIG.

FIG. 12 is a diagram showing an example of a filter for performing color noise smoothing processing in FIG. 9.

FIG. 13 is a block diagram showing an example of an image processing apparatus according to an embodiment.

[Explanation of symbols]

100 host computer 101 Application software 102 Operating system (OS) 103 printer driver 104 monitor driver 105 monitor 106 printer 107 Hard disk driver (HD) 108 Central processing unit (CPU) 109 Random access memory (RAM) 110 Read-only memory (ROM) 120 Image correction processing unit 121 Printer correction processing unit 1301 Edge extraction unit 1302 Edge determination unit 1303 Brightness enhancement section 1303 'Luminance smoothing unit 1304 Color noise determination unit 1305 Color noise smoothing section 1306 Y / C separation unit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 9/64 H04N 1/40 DF term (reference) 5B057 CA01 CA02 CA08 CA12 CA16 CB01 CB02 CB08 CB12 CB16 CC01 CE02 CE05 CE06 CE16 CH08 5C066 AA01 CA07 EC02 EC12 GA01 KM02 5C077 LL02 MP01 MP07 MP08 PP01 PP02 PP32 PP34 PP37 PP68 PQ12 5C079 HB01 HB04 LA14 MA11 NA02 5L096 AA02 EA05 FA06 GA55 MA03

Claims (27)

[Claims] 1. The image data is classified into a contour portion and a non-contour portion, and noise generated in a signal representing the brightness forming the image data is subjected to noise removal processing on the non-contour portion. An image processing apparatus, wherein noise removal processing is performed on noise generated in a signal representing a tint that constitutes the image data according to a generation status of noise generated in the color signal. 2. In an image processing device for removing noise generated in an image, a contour extracting means for subjecting a signal representing the brightness of the image to a contour extracting filter process to extract a contour of the image, and the contour extracting means. First smoothing means for performing a smoothing process on a signal representing the brightness of a portion other than the contours extracted by the means; color noise determining means for determining color noise in the image; and color noise determination Based on the color noise determination made by the means, a color noise detecting means for checking whether or not the pixel of interest is a color noise portion generated in the signal representing the tint; An image processing apparatus comprising: a second smoothing unit that performs a smoothing process on a signal representing a tint with respect to a color noise portion. 3. The image processing apparatus according to claim 2, wherein the signal representing the brightness is a luminance signal and the signal representing the tint is a color difference signal. 4. The image processing apparatus according to claim 2, wherein the signal representing the brightness is subjected to smoothing processing according to the generation state of the color noise portion detected by the color noise detecting means. . 5. The selection process of a portion to which a smoothing process is applied to the signal representing the tint is independent of the contour part of the image obtained from the signal representing the brightness. The image processing device according to any one of 2 to 4. 6. The contour extracting means according to claim 2, wherein when an isolated point is generated, the remaining portion from which the isolated point is removed is extracted as a contour. Image processing device. 7. The image processing apparatus according to claim 2, wherein the contour extracting unit for the signal representing the brightness uses a Laplacian filter process or a high pass filter process. 8. The color noise determining means obtains the difference between the signals representing the tint of the pixel of interest and its neighboring pixels, and performs threshold value determination on the result of the difference to determine that the pixel of interest has a color noise portion. The image processing apparatus according to claim 2, wherein the image processing apparatus determines whether or not 9. The contour portion extracted by the contour extracting means further comprises enhancement means for performing enhancement processing on a signal representing brightness.
The image processing device according to item. 10. The contour extracting means, the first smoothing means, and the second smoothing means are provided with a plurality of filters for performing filter processing on the signal representing the brightness according to the image to be corrected. 9. The image processing apparatus according to claim 2, further comprising a filter selection unit that selects from the inside. 11. The contour extracting means, the first smoothing means, the second smoothing means, and the emphasizing means for performing filter processing to be applied to the signal representing the brightness according to the image to be corrected. The image processing apparatus according to claim 9, further comprising a filter selection unit that selects a filter from a plurality of filters. 12. A printer driver using the image processing apparatus according to any one of claims 1 to 11. 13. The image data is classified into a contour portion and a non-contour portion, and noise generated in a signal representing brightness forming the image data is subjected to noise removal processing on the non-contour portion. An image processing method is characterized in that noise removal processing is performed on noise generated in a signal representing a tint constituting the image data according to a generation status of noise generated in the color signal. 14. An image processing method for removing noise generated in an image, the contour extraction process of subjecting a signal representing the brightness of the image to a contour extraction filter process to extract the contour of the image, and the contour extraction. A first smoothing process for performing a smoothing process on a signal representing the brightness of a portion other than the contours extracted in the process; a color noise determining process for determining a color noise in the image; and a color noise determining process. Based on the color noise determination determined by the processing, the color noise detection processing for checking whether the pixel of interest is the color noise portion generated in the signal representing the tint, and the color noise detection processing for detecting the color noise An image processing method, comprising: a second smoothing process for performing a smoothing process on a signal representing a tint with respect to a color noise portion. 15. The image processing method according to claim 14, wherein the signal representing the brightness is a luminance signal, and the signal representing the tint is a color difference signal. 16. The smoothing process is performed on the signal representing the brightness according to the generation state of the color noise portion detected by the color noise detecting process.
Alternatively, the image processing method according to Item 15. 17. The selection process of a portion for performing smoothing processing on the signal representing the tint is independent of the contour portion of the image obtained from the signal representing the brightness. The image processing method according to any one of 14 to 16. 18. The outline extracting process according to claim 14, wherein when an isolated point is generated, the remaining part from which the isolated point is removed is extracted as an outline.
The image processing method according to any one of 1. 19. The Laplacian filter process or a high-pass filter process is used for the contour extraction process for the signal representing the brightness.
The image processing method according to any one of 1. 20. The color noise determination process obtains a difference between signals representing the tint of a pixel of interest and its neighboring pixels, and performs threshold determination on the result of the difference to determine that the pixel of interest is a color noise part. 20. The image processing method according to claim 14, wherein it is determined whether or not 21. The image processing method according to claim 14, wherein in the contour portion extracted by the contour extraction processing, a signal representing brightness is enhanced. 22. In the contour extracting process, the first smoothing process, and the second smoothing process, a plurality of filters are provided for performing a filtering process on the signal representing the brightness according to the correction target image. 21. The method according to claim 14, further comprising a filter selection process for selecting from among them.
The image processing method described in the item. 23. In the contour extracting process, the first smoothing process, the second smoothing process, and the emphasizing process, a filter process is performed on a signal representing the brightness according to a correction target image. The image processing method according to claim 21, further comprising a filter selection process of selecting a filter from a plurality of filters. 24. In a recording medium storing a computer readable program, contour data extraction processing is performed on a luminance signal, and smoothing processing is performed on a luminance signal and a color difference signal of a portion other than the contour to obtain image data. A computer-readable recording medium storing a correction program. 25. A computer-readable storage medium on which a program for causing a computer to function as each unit according to claim 1 is recorded. 26. A computer-readable storage medium having recorded thereon a program for causing a computer to execute the image processing method according to any one of claims 13 to 23. 27. A computer program causing a computer to execute the image processing method according to any one of claims 13 to 23.