JP5535443B2 - Image processing device - Google Patents

Description

  The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus having a coring unit that performs correction processing on a color difference signal.

  In general, an image processing apparatus performs image processing such as pixel interpolation, color conversion, contour correction processing, filtering, and thinning processing on an image signal output from an imaging unit. The image signal after each image processing is stored as image data in a predetermined built-in memory.

  One of the image processes is a coring process. FIG. 8 shows the state of coring processing for the color difference signals Cb and Cr. In FIG. 8, the horizontal axis represents the color component of the input color difference signal, and the vertical axis represents the color component of the output color difference signal. In FIG. 8, the color component becomes higher (the gradation becomes higher and the saturation becomes higher) as going in the right direction of the horizontal axis or the upward direction of the vertical axis.

  In FIG. 8, the dotted line indicates the relationship between the color component of the input color difference signal and the color component of the output color difference signal before coring processing. The solid line indicates the relationship between the color component of the input color difference signal and the color component of the output color difference signal after coring processing.

  As shown in FIG. 8, in the conventional coring process, correction (zero clip correction) is performed on the input color difference signal having the first color component A1 from zero. Then, for the input color difference signal having a color component higher than the first color component A1, correction for reducing the saturation by a certain amount is performed.

  If the coring process is not performed, the color component of the input color difference signal and the color component of the output color difference signal are the same. However, by applying the conventional coring process shown in FIG. 8 to the input color difference signal, the low-saturation color component is zero-clipped, and the medium-high saturation color component is reduced by a certain amount. .

  Thus, the coring process is performed on the input color difference signal. Thereby, noise generated due to the imaging unit or the like can be suppressed at a low saturation level.

  For example, Patent Documents 1 and 2 exist as conventional documents that have a description of coring processing.

JP 2000-236473 A JP 2007-31331 A

  However, when the coring process shown in FIG. 8 is performed, zero clipping is performed for a predetermined coring amount threshold. Therefore, there arises a problem that the overall gradation of the saturation is impaired.

  Therefore, an object of the present invention is to provide an image processing apparatus that can suppress noise generated due to an imaging unit or the like at a low saturation level and that does not impair the gradation of saturation.

In order to achieve the above object, an image processing apparatus according to claim 1 of the present invention includes a color space conversion unit that converts a color space of an image signal into a color space defined by a luminance signal and a color difference signal. And a coring unit that corrects the input color difference signal, and the coring unit performs correction to reduce saturation with respect to the color difference signal having the first color component from zero. The color difference signal having a color component higher than the first color component is not subjected to correction for reducing saturation, and the coring unit performs the color difference signal having the first color component from zero. On the other hand, the first correction is performed to linearly increase the degree of decrease in saturation as the color component increases.

The image processing device according to claim 2 is the image processing device according to claim 1 , wherein the coring unit has a second higher than the first color component from the first color component. The color difference signal having a color component is subjected to a second correction that lowers the degree of saturation as the color component increases, and the color difference signal having a color component higher than the second color component is applied to the color difference signal. On the other hand, no correction for decreasing the saturation is performed.

An image processing apparatus according to claim 3 is the image processing apparatus according to claim 2 , wherein the first color component width from zero to the first color component and the first color component To the second color component is the same size.

An image processing apparatus according to a fourth aspect is the image processing apparatus according to the second aspect , further including a setting change processing unit capable of changing the first color component to an arbitrary value.

The image processing apparatus according to claim 5, an image processing apparatus according to claim 2, the setting change processing unit capable of changing the second color component to an arbitrary value, and further comprising.

Further, the image processing apparatus according to claim 6, an image processing apparatus according to claim 1, the setting change processing unit capable of changing the correction degree of the first correction to an arbitrary value, further comprising with Yes.

Further, the image processing apparatus according to claim 7, an image processing apparatus according to claim 2, the setting change processing unit capable of changing the correction degree of the second correction to an arbitrary value, further comprising with Yes.

  An image processing apparatus according to claim 1 of the present invention includes an imaging unit, a color space conversion unit that converts an image signal output from the imaging unit into a color space defined by a luminance signal and a color difference signal, and an input A coring unit that performs correction for the color difference signal to be generated, and the coring unit performs correction for reducing the saturation with respect to the color difference signal having the first color component from zero, so that the first color The color difference signal having a higher color component than the component is not corrected to reduce the saturation.

  Therefore, noise generated due to the imaging unit or the like can be suppressed at a low saturation level, and gradation can be prevented from being damaged in a high saturation region.

In the image processing apparatus according to claim 1 , the coring unit linearly increases the degree of decrease in saturation as the color component increases with respect to the color difference signal having the first color component from zero. Increase the first correction.

  Therefore, the noise can be reduced while ensuring the degree of saturation of the output color difference signal in the low saturation region.

In the image processing apparatus according to claim 2 , the coring unit increases the color component with respect to the color difference signal having the second color component higher than the first color component from the first color component. Accordingly, the second correction is performed to lower the degree of decrease in saturation, and correction for decreasing the saturation is not performed on the color difference signal having a color component higher than the second color component.

  Therefore, it is possible to solve the problem that the output image is damaged as described above, and it is also possible to prevent the gradation of the output color difference signal from being damaged in the high saturation region.

The image processing apparatus according to claim 3 , wherein the first color component width from zero to the first color component, and the second color component width from the first color component to the second color component, Are the same size.

  Therefore, the configuration of the coring unit can be simplified.

The image processing device according to any one of claims 4 to 7 further includes a setting change processing unit. The setting changing unit can change the value of the first color component, the value of the second color component, the correction degree of the first correction, and the correction degree of the second correction to arbitrary values.

  Accordingly, each parameter can be set so as to obtain an appropriate effect according to the characteristics of the image processing apparatus itself and the situation in which it is used.

  Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.

<Embodiment>
FIG. 1 is a block diagram showing a configuration of an image processing apparatus 100 according to the present embodiment.

  As shown in FIG. 1, the image processing apparatus 100 includes an imaging unit 10, an image processing unit 20, an interpolation unit 30, a color space conversion unit 40, a spatial filter / coring unit 50, a setting change unit 60, and a memory 70. ing.

  The imaging unit 10 images a subject and outputs the imaging result as an image signal. As the imaging unit 10, a CCD (Charge Coupled Device) sensor, a CMOS (Complementary Metal Oxide Semiconductor) sensor, or the like can be employed.

  The image processing unit 20 converts the analog image signal output from the imaging unit 10 into a digital image signal. Then, the image processing unit 20 performs a temporal averaging process, a shading correction process, and the like on the digital image signal.

  In the temporal averaging process, when the accumulation time of the imaging unit 10 extends over a plurality of frames, data is read from the imaging unit 10 for each frame and added to the data of the corresponding pixel on the memory 70. In general, when a subject is photographed by the imaging unit 10, shading occurs that the surroundings are darker than the brightness at the center position due to the optical action of the lens. In the shading correction process, gain adjustment such as a luminance value of each pixel is performed in order to reduce the shading.

  In the interpolation unit 30, general pixel interpolation is performed in the digital image captured by the imaging unit 10, in which a new pixel is artificially created between the adjacent pixels from information between adjacent pixels. The interpolation unit 30 performs general gamma correction that corrects the gamma value, which is the ratio of the change in voltage conversion value to the change in image brightness. In the gamma correction, the relative relationship between color data such as an image and a signal when it is actually output is adjusted. Thereby, a more natural display can be obtained.

  The color space conversion unit 40 converts the image signal subjected to pixel interpolation by the interpolation unit 30 into a color space defined by the luminance signal Y and the color difference signals Cr and Cb. The converted color space signals Y, Cb, and Cr are output in parallel to the subsequent spatial filter / coring unit 50.

  The spatial filter / coring unit 50 has the configuration shown in FIG.

  As shown in FIG. 2, the spatial filter / coring unit 50 includes three spatial filters 51Y, 51U, and 51V and two coring units 52U and 52V. Here, although not shown in FIG. 2, the coring units 52 </ b> U and 52 </ b> V are connected to the setting changing unit 60.

  The luminance signal Y output from the color space conversion unit 40 is input to the spatial filter 51Y. The color difference signal Cb output from the color space conversion unit 40 is input to the spatial filter 51U. The color difference signal Cr output from the color space conversion unit 40 is input to the space filter 51V.

  A signal output from the spatial filter 51U is input to the memory unit 70 via the coring 52U. The signal output from the spatial filter 51V is input to the memory unit 70 via the coring 52V. In the configuration shown in FIG. 2, the signal output from the spatial filter 51 </ b> Y is directly input to the memory unit 70. However, a coring unit that performs a predetermined coring process may be disposed between the spatial filter 51Y and the memory unit 70.

  In the spatial filters 51Y, 51U, 51V, the color space signals Y, Cb, Cr are subjected to smoothing processing for weakening noise, contour enhancement processing for enhancing edge portions, and color suppression (chroma suppress) for bright and dark portions in an image. : False color suppression processing is performed. The processed color space signals Y, Cb, and Cr are output to the memory unit 70 and the coring units 52U and 52V as described above.

  The coring units 52U and 52V correct the input color difference signals Cb and Cr. In addition, the specific correction | amendment operation | movement of the coring parts 52U and 52V which concerns on this Embodiment is mentioned later. In addition, although different from FIG. 2, when a coring unit that performs a predetermined correction on the luminance signal Y is provided, the coring unit is disclosed in, for example, Patent Documents 1 and 2 above. Make corrections.

  In FIG. 1, a setting changing unit 60 is a part that can change and set parameters set in the coring units 52U and 52V. The color space signals Y, Cb, and Cr that have been subjected to each process in the spatial filter / coring unit 50 are stored as image data in a predetermined internal memory.

<Operation in the coring portions 52U and 52V>
Next, correction (coring processing) performed in the coring units 52U and 52V will be described with reference to FIG. Since the coring units 52U and 52V perform the same operation, the coring unit 52U will be described here as a representative.

  FIG. 3 shows a state of coring processing for the color difference signal Cb. In FIG. 3, the horizontal axis represents the color component of the input color difference signal Cb, and the vertical axis represents the color component of the output color difference signal Cb. In FIG. 3, the color component becomes higher (the gradation becomes higher and the saturation becomes higher) as going in the right direction of the horizontal axis or the upward direction of the vertical axis.

  In FIG. 3, the dotted line indicates the relationship between the color component of the input color difference signal Cb and the color component of the output color difference signal Cb before coring processing. The solid line shows the relationship between the color component of the input color difference signal Cb and the color component of the output color difference signal Cb after coring processing. As can be seen from the dotted line in FIG. 3, the color component of the input color difference signal Cb and the color component of the output color difference signal Cb are the same unless the coring process is performed on the input color difference signal Cb.

  In the present specification, an area from 0 to the first color component a (the value of a can be set to an arbitrary value) is referred to as a “low saturation area”. Further, an area from the first color component a to the second color component 2a (which may not be a multiple of a, and an arbitrary value can be set for the value of the second color component) is referred to as a “medium chroma region”. Called. Furthermore, a region of a color component higher than the second color component 2a is referred to as a “high saturation region”.

  As shown in FIG. 3, the coring unit 52U performs correction (coring processing) to reduce saturation at least for the color difference signal Cb having the first color component a from zero. Further, the coring unit 52U performs correction (core) for reducing the saturation with respect to the color difference signal Cb having a high-frequency component higher than the first color component a (a color component higher than the color component 2a in FIG. 3). (Ring processing) is not performed.

  Specifically, the coring unit 52U reduces the saturation with respect to the input color difference signal Cb having the color component of the low saturation region as the color component becomes higher (as it goes in the right direction in the drawing). A first correction (first coring process) is performed to increase the degree. That is, in FIG. 3, in the low saturation region, the width of the dotted line and the solid line (the degree to which the saturation is reduced) increases as the color component increases. The color component of the output color difference signal Cb after the first correction is b / a × (color component of the input color difference signal Cb).

  Further, the coring unit 52U increases the degree of decrease in saturation as the color component becomes higher (as it goes in the right direction in the drawing) with respect to the input color difference signal Cb having the color component in the middle saturation region. A second correction (second coring process) is performed to lower the value. That is, in the middle saturation region in FIG. 3, the width of the dotted line and the solid line (the degree to which the saturation is reduced) decreases as the color component increases. The color component of the output color difference signal Cb after the second correction is (2-b / a) × (color component of the input color difference signal Cb).

  Further, the coring unit 52U does not perform correction to reduce the saturation for the input color difference signal Cb having the color component of the high saturation region.

  Note that the slope of the solid line is used as an index indicating the correction degree of the first and second corrections. The smaller the inclination, the greater the degree of correction (the greater the color component of the input color difference signal Cb, the more the saturation is reduced). In other words, the greater the inclination, the smaller the correction degree (the higher the color component of the input color difference signal Cb, the less the saturation is reduced). In the first correction, the inclination is less than 1 (including zero). In the second correction, the slope is larger than 1. In the case of no correction, the slope is 1.

  The setting change unit 60 receives an input operation from the outside. Then, the setting change unit 60 performs control to change / set each parameter stored in a register (not shown) in the coring unit 52U. For example, the setting change unit 60 performs control to change / set the values of the first color component a and the second color component 2a to arbitrary values according to the input operation. The setting changing unit 60 performs control for changing and setting the correction degree of the first and second corrections (the inclinations a / b and 2-b / a) to arbitrary values according to the input operation. Do.

  As described above, in the image processing apparatus 100 according to the present embodiment, the coring units 52U and 52V reduce the saturation with respect to the input color difference signals Cb and Cr having at least color components in the low saturation region. Corrections are being made. Further, the coring units 52U and 52V do not perform the correction for reducing the saturation on the input color difference signals Cb and Cr having the color components in the high saturation region.

  Therefore, noise generated due to the imaging unit 10 and the like can be suppressed at a low saturation level, and the gradation can be prevented from being damaged with respect to the high saturation region.

  In the image processing apparatus 100 according to the present embodiment, the coring units 52U and 52V perform the first correction on the input color difference signals Cb and Cr having the color components in the low saturation region. .

  Therefore, the noise can be reduced while ensuring the degree of saturation of the output color difference signal in the low saturation region.

  As shown in FIG. 4, the coring units 52U and 52V perform the first correction on the input color difference signals Cb and Cr having the first color component from zero, and are higher than the first color component. The input color difference signals Cb and Cr having color components may not be corrected. That is, a configuration in which the second correction is omitted may be used.

  However, when the operation shown in FIG. 4 is performed, the presence / absence of correction changes rapidly, so that the output image is damaged in the vicinity of the first color component.

  Therefore, in the image processing apparatus 100 according to the present embodiment, the coring units 52U and 52V perform the second correction on the input color difference signals Cb and Cr having the color components in the middle saturation region. . Then, the coring units 52U and 52V do not perform correction for reducing the saturation on the input color difference signals Cb and Cr having the color components in the high saturation region.

  Therefore, it is possible to solve the problem that the output image is damaged as described above, and it is also possible to prevent the gradation of the output color difference signal from being damaged in the high saturation region.

  As described above, the correction degree of the first correction can be arbitrarily changed. Therefore, for example, as shown in FIG. 5, the coring units 52U and 52V perform color components for input color difference signals Cb and Cr having color components in the low saturation region (0 to the first color component a). Zero clip correction may be performed to make the value zero. That is, the inclination, which is an index of the first correction degree, is zero.

  By adopting such coring units 52U and 52V that perform the operation shown in FIG. 5, noise caused by the imaging unit 10 and the like can be completely suppressed at a low saturation level.

  As described above, the values of the first color component a and the second color component 2 a can be selected and changed to arbitrary values under the control of the setting change unit 60. Therefore, for example, as shown in FIGS. 6 and 7, these values stored in registers (not shown) in the coring units 52U and 52V may be changed. That is, in FIG. 6, the first color component is “c” and the second color component is “d”. Here, the color component width from zero to the first color component c (the low saturation region and the region where the first correction is performed) is from the first color component c to the second color. It is larger than the color component width up to the component d (intermediate saturation region and region where the second correction is performed). In FIG. 7, the first color component is “f” and the second color component is “g”. Here, the color component width from zero to the first color component f (the low saturation region and the region where the first correction is performed) is the first color component f to the second color. It is smaller than the color component width up to the component g (intermediate saturation area, which is subjected to the second correction).

  However, in the case shown in FIG. 3, the color component width from zero to the first color component a (the low saturation region, the region to which the first correction is applied) and the first color component. The color component width from a to the second color component 2a (intermediate saturation region, the region to which the second correction is applied) is the same size.

  Thus, the value of the first color component and the value of the second color component are set so that the size of the region subjected to the first correction and the region subjected to the second correction have the same width. Select. Thereby, the structure of the coring parts 52U and 52V can be simplified.

  Further, in the image processing apparatus 100 according to the present embodiment, the parameters stored in the coring units 52U and 52V (the values of the first and second color components, the degree of correction of the first and second corrections). (The above inclination)) can be changed / set.

  Accordingly, each parameter can be set so as to obtain an appropriate effect according to the characteristics of the image processing apparatus 100 itself and the situation in which it is used.

  The color component notations in FIGS. 3 to 7 are absolute value notations.

It is a block diagram which shows the structure of the image processing apparatus which concerns on this invention. It is a block diagram which shows the internal structure of a spatial filter coring part. It is a figure for demonstrating operation | movement of a coring part. It is a figure for demonstrating operation | movement of a coring part. It is a figure for demonstrating operation | movement of a coring part. It is a figure for demonstrating operation | movement of a coring part. It is a figure for demonstrating operation | movement of a coring part. It is a figure for demonstrating the conventional coring operation | movement.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image pick-up part 20 Image processing part 30 Interpolation part 40 Color space conversion part 50 Spatial filter and coring part 51Y, 51U, 51V Spatial filter 52U, 52V Coring part 60 Setting change part 70 Memory 100 Image processing apparatus Y Luminance signal Cb, Cr color difference signal

Claims (7)

A color space conversion unit that converts the color space of the image signal into a color space defined by a luminance signal and a color difference signal;
A coring unit that performs correction on the input color difference signal,
The coring part is
For the color difference signal having the first color component from zero, a correction to reduce the saturation is performed,
The color difference signal having a color component higher than the first color component is not corrected to reduce saturation ,
The coring part is
An image characterized by performing a first correction for linearly increasing the degree of saturation reduction as the color component increases with respect to the color difference signal having the first color component from zero. Processing equipment. The coring part is
A second correction is performed in which the color difference signal having a second color component higher than the first color component from the first color component is decreased as the color component is increased. Done
The color difference signal having a color component higher than the second color component is not corrected to reduce saturation.
The image processing apparatus according to claim 1. A first color component width from zero to the first color component;
The second color component width from the first color component to the second color component is the same size.
The image processing apparatus according to claim 2 . A setting change processing unit capable of changing the first color component to an arbitrary value;
The image processing apparatus according to claim 2 . A setting change processing unit capable of changing the second color component to an arbitrary value;
The image processing apparatus according to claim 2 . A setting change processing unit capable of changing the correction degree of the first correction to an arbitrary value ;
The image processing apparatus according to claim 2 . A setting change processing unit capable of changing the correction degree of the second correction to an arbitrary value ;
The image processing apparatus according to claim 2 .

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