JP4950582B2 - Video signal processing device - Google Patents

Description

  The present invention relates to a video signal processing apparatus for automatically adjusting white balance, such as an electronic camera or a video camera.

  Conventionally, a video signal processing apparatus that adjusts the white balance of a video signal is known. In an example of a conventional video signal processing apparatus, color component signals R (red), G (green), and B (blue) are input as video signals. An achromatic region in the video signal is selected, and the R, G, and B signals in the selected region are integrated to calculate average values Ra, Ga, and Ba. Further, average ratios Ra / Ga and Ba / Ga are calculated, and white balance adjustment is performed using these ratios.

  FIG. 6 shows a color signal ratio characteristic curve used for white balance adjustment in the prior art. In FIG. 6, the horizontal axis is R / G and the vertical axis is B / G. The color signal ratio characteristic curve L shows the relationship between R / G and B / G in a state where the white balance is adjusted.

In white balance adjustment, a point a (Ra / Ga, Ba / Ga) in the figure is obtained from the average values Ra, Ga, Ba of the color component signals. Then, a point a ′ (Ra ′ / Ga ′, Ba ′ / Ga ′) on the color signal ratio characteristic curve L close to the point a is obtained. The point a ′ is obtained, for example, so that the distance from the point a is the shortest. Then, the reciprocals of Ra ′ / Ga ′ and Ba ′ / Ga ′ are multiplied by the color components R and G of the video signal, respectively, thereby performing white balance adjustment (see, for example, Patent Document 1).
Japanese Patent Application Laid-Open No. 11-262021

  However, the conventional video signal processing apparatus has the following problems.

  In the prior art, as described above, the R, G, and B signals are integrated to obtain the average values Ra, Ga, and Ba, and the average ratios Ra / Ga and Ba / Ga are calculated. The balance is being adjusted. In this case, a subject with a high luminance level has a large contribution to the integrated value because the RGB signal is large, and therefore white balance adjustment is easily affected by luminance. Also, a subject with a large area also has a large contribution to the average value, and white balance adjustment is easily influenced by a subject with a large area.

  As described above, the conventional white balance adjustment is easily influenced by a high-luminance subject or a large-area subject that has a large contribution to the RGB integrated value. On the other hand, since it is generally difficult to integrate only achromatic pixels in an image during white balance adjustment, pixels with a light color to some extent are included in the integrated value. For this reason, the prior art has a problem that the white balance may be shifted under the influence of the luminance and area of a subject that is not an achromatic color.

  The present invention has been made to solve the conventional problems, and an object thereof is to provide a video signal processing apparatus capable of adjusting white balance with higher accuracy.

  The video signal processing apparatus of the present invention calculates a frequency of the coordinate signal in the two-dimensional coordinate system, and a two-dimensional coordinate conversion means for converting the video signal into a coordinate signal of a two-dimensional coordinate system indicating color information. Histogram calculating means for obtaining a two-dimensional coordinate histogram by means of, and representative point coordinate calculating means for obtaining representative point coordinates representing the coordinate signal group obtained by the two-dimensional coordinate conversion means according to the frequency of the two-dimensional coordinate histogram. And gain adjusting means for performing white balance adjustment based on the representative point coordinates.

  With this configuration, a video signal is converted into a coordinate signal of a two-dimensional coordinate system indicating color information, a frequency of the coordinate signal is calculated, a two-dimensional coordinate histogram is obtained, and a representative point coordinate of the two-dimensional coordinate system histogram is obtained. , Adjust the white balance using the representative point coordinates. As described above, according to the present invention, the video signal is converted into the coordinate signal of the color information in the two-dimensional coordinate system, and then the white balance adjustment is performed using the representative point coordinates of the coordinate signal group, thereby obtaining a highly accurate white. Balance adjustment can be performed.

  In the video signal processing apparatus of the present invention, the two axes of the two-dimensional coordinate system are blue / green and red / green, blue / luminance and red / luminance, or (blue-green) / luminance. (Red-green) / luminance, or (blue-luminance) / luminance and (red-luminance) / luminance.

  With this configuration, the luminance component in the coordinate signal of the two-dimensional coordinate system is reduced, and a histogram is created from such a coordinate signal to perform white balance adjustment. Accordingly, highly accurate white balance adjustment with reduced influence of the luminance level can be performed.

  In the video signal processing apparatus of the present invention, the representative point coordinate calculation means obtains the coordinates of the centroid position of the coordinate signal group by a weighted average using the frequency of the two-dimensional coordinate histogram, and obtains the coordinates of the centroid position. It is comprised so that it may be set as a representative point coordinate.

  With this configuration, since the coordinates of the barycentric position of the coordinate signal group are obtained by a weighted average using the frequency of the two-dimensional coordinate histogram, it is possible to obtain appropriate representative point coordinates that represent the coordinate signal group obtained from the video.

  In the video signal processing device of the present invention, the representative point coordinate calculation means may weight the frequency according to the frequency magnitude with respect to the frequency of the coordinate signal at each position of the two-dimensional coordinate system. And the barycentric position of the coordinate signal group is obtained by a weighted average using the weighted frequency.

  With this configuration, since weighting is performed according to the frequency, the influence of a subject with a large area can be reduced, and highly accurate white balance adjustment can be performed.

  In the video signal processing apparatus of the present invention, the representative point coordinate calculation unit is configured to perform weighting so that the frequency of the coordinate signal at each position in the two-dimensional coordinate system is equal to or less than a frequency upper limit value. Yes. With this configuration, the frequency of the coordinate signal is limited to a frequency upper limit value or less, so that the influence of a subject with a large area can be reduced and highly accurate white balance adjustment can be performed.

  In the video signal processing apparatus of the present invention, the representative point coordinate calculating means excludes the frequency from the weighted average target when the frequency of the coordinate signal at each position in the two-dimensional coordinate system is equal to or lower than a frequency lower limit value. In this way, weighting is performed. With this configuration, it is possible to exclude coordinate signals with a low frequency from the calculation target of the weighted average, reduce the influence of noise, and perform white balance adjustment with high accuracy.

  In the video signal processing device of the present invention, the representative point coordinate calculation unit is configured to change the weighted frequency according to a feature amount representing a feature of the two-dimensional coordinate histogram, and the feature amount is It is at least one of the maximum value of the frequency, the minimum value of the frequency, the average value of the frequency, and the standard deviation of the frequency. With this configuration, it is possible to appropriately adjust the weighting frequency according to the feature amount of the two-dimensional coordinate histogram, and it is possible to perform highly accurate white balance adjustment that further reduces the influence of area and noise.

  In the video signal processing apparatus of the present invention, the representative point coordinate calculation unit is weighted by weighting the frequency of the coordinate signal at each position in the two-dimensional coordinate system according to the coordinate position of the coordinate signal. The frequency is obtained, and the barycentric position of the coordinate signal group is obtained by a weighted average using the weighted frequency. With this configuration, highly accurate white balance adjustment with reduced influence of chromatic colors can be performed.

  In the video signal processing apparatus of the present invention, the representative point coordinate calculating means calculates the weighted frequency according to the coordinate position, and the coordinates of coordinates located in the achromatic region and in the vicinity thereof in the two-dimensional coordinate system. The weight is set to be higher than the weight of the coordinates located in the chromatic color region. With this configuration, highly accurate white balance adjustment with reduced influence of chromatic colors can be performed.

  Further, the video signal processing method of the present invention converts the video signal into a coordinate signal of a two-dimensional coordinate system indicating color information, and calculates the frequency of the coordinate signal in the two-dimensional coordinate system, thereby calculating the two-dimensional coordinate. A histogram is obtained, representative point coordinates representing a coordinate signal group converted from the video signal are obtained according to the frequency of the two-dimensional coordinate histogram, and white balance adjustment is performed based on the representative point coordinates. This aspect also provides the above-described advantages of the present invention.

  In the present invention, the video signal is converted into a coordinate signal of a two-dimensional coordinate system indicating color information, and white balance adjustment is performed using the representative point coordinates of the coordinate signal group obtained from the frequency of the coordinate signal. It is possible to provide a video signal processing apparatus having an effect that a highly accurate white balance adjustment which is not easily influenced by a level or the like can be performed.

  Hereinafter, a video signal processing apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  A video signal processing apparatus according to the first embodiment of the present invention is shown in FIG.

  The video signal processing apparatus 1 in FIG. 1 is provided in an imaging apparatus such as a digital camera, for example. In this case, a video signal generated by an imaging device such as a CCD is input to the video signal processing device 1. Then, the video signal processing apparatus 1 performs white balance adjustment and outputs the adjusted video signal. The video signal after the white balance adjustment is subjected to other processing, recorded on a memory and a recording medium, displayed on a display, for example, and output to the outside via a network or the like.

  In FIG. 1, a video signal processing apparatus 1 according to the present embodiment includes a two-dimensional coordinate conversion unit 2 that converts a video signal into a coordinate signal of a two-dimensional coordinate system indicating color information, and a two-dimensional coordinate conversion unit 2. A histogram calculation unit 3 that calculates an appearance frequency of coordinates to be output to create a two-dimensional coordinate histogram; a representative point coordinate calculation unit 4 that calculates a representative point coordinate representing a coordinate signal group according to the frequency of the two-dimensional coordinate histogram; And a gain adjusting unit 5 that performs white balance gain adjustment based on the representative point coordinates.

  The video signal processing apparatus 1 may be configured by a circuit that realizes the various functions described above. Further, the video signal processing apparatus 1 may be realized by storing a program that realizes the same function in an imaging device or the like and executing the program by an arithmetic device.

  The operation of the video signal processing apparatus 1 configured as described above will be described.

  In this embodiment, a case where an input video signal is an RGB signal will be described. In RGB signals obtained by imaging a subject, the RGB component balance differs depending on the spectral characteristics of the light source, and this balance needs to be adjusted. This adjustment process is performed as follows.

  First, the two-dimensional coordinate conversion unit 2 converts the RGB signal into a two-dimensional coordinate system coordinate signal (x, y) indicating color information. In this case, the two-dimensional coordinate condition requires that the color can be identified and that the influence of the luminance level (brightness and darkness) is small. The two-dimensional coordinate system that satisfies this condition is (B / G, R / G), (B / G, R / G), (B / Y, R / Y), or ((B−G) / Y, (R−G) / Y) or ((B−Y) / Y, (R−Y) / Y).

  Here, Y is the luminance. Since G (green) is close to luminance, it can be used as a parameter representing the luminance level in video processing. Therefore, in the present embodiment, the coordinate signal of the two-dimensional coordinates is a color ratio signal divided by a luminance parameter such as a G signal or a Y signal. By dividing the color signal by the G signal or the Y signal to obtain a ratio, the influence of the luminance level can be reduced.

  In addition to these parameters, two independent axes can be set. Hereinafter, in this embodiment, an example in which the two-dimensional coordinate system is (B / G, R / G) will be described, but other coordinate systems are also applicable to the present invention.

  Next, frequency calculation is performed on the coordinate signals (B / G, R / G) converted into two-dimensional coordinates by the histogram calculation unit 3 to create a two-dimensional coordinate histogram shown in FIG. . The two-dimensional coordinate histogram is a histogram of the appearance frequency of each coordinate signal in the two-dimensional coordinate system.

  As shown in FIG. 2, the two-dimensional coordinate system is divided into a number of predetermined regions. The frequency of coordinate signals for one screen is calculated for each region, and a two-dimensional coordinate histogram is calculated. Although FIG. 2 is simplified, in practice more regions may be provided. For example, the range where the x-axis B / G is 0 to 4 is divided into 100, the y-axis R / G is also divided into 100 the range from 0 to 4, and 10,000 areas are set in a grid pattern.

  Note that coordinates with extremely large or small B / G or R / G correspond to dark chromatic colors, so such parts can be omitted from the frequency calculation, thereby reducing the circuit. Is possible.

  Further, when obtaining the frequency, it is preferable to exclude signals that are too bright and saturated because the RGB balance is shifted. Further, when the divisor G or Y is small, the error of the division result becomes large. Therefore, the accuracy can be further improved by excluding such a small divisor signal.

  Next, the representative point coordinates are obtained by the representative point coordinate calculation unit 4 using the frequency thus obtained. The representative point coordinates are the coordinates of a representative point representing a coordinate signal group obtained from one screen. In the present embodiment, the representative point coordinates are coordinates of the center of gravity position obtained by weighted the coordinate signals using the frequency of the two-dimensional coordinate histogram. Furthermore, in the present embodiment, weighting is performed on the frequency of the coordinate signal at the time of load averaging. Here, a simple weighted average will be described first, and then a weighted average obtained by weighting will be described.

If the frequency of each region obtained by the histogram calculation unit 3 is H (x, y), the center of gravity position of the coordinate signal group is calculated by the weighted average of the coordinates (x, y) and the frequency H (x, y). it can. The center of gravity (Wx0, Wy0) is expressed by the following equation.
Wx0 = Σ [x · H (x, y)] / ΣH (x, y)
Wy0 = Σ [y · H (x, y)] / ΣH (x, y)

  However, Σ indicates the total sum of the entire (x, y) two-dimensional coordinates (in the example of FIG. 2, the total sum of all areas set in the two-dimensional coordinate histogram).

  This barycentric position is obtained from coordinate signals in a two-dimensional coordinate system. And the coordinate signal of this Embodiment is a parameter with little influence of a brightness | luminance as mentioned above. Therefore, representative point coordinates with reduced influence of the luminance level can be obtained by the above-described processing.

  However, the simple barycentric position described above directly reflects the magnitude of the frequency. In the two-dimensional coordinate histogram, the frequency of the two-dimensional coordinates corresponding to the color of the portion having a large area is large. Therefore, when a simple center of gravity position is used, there remains a problem that the influence of a large area is increased. Therefore, in the present embodiment, the frequency is weighted according to the magnitude thereof as follows. Then, the centroid position is calculated using the weighted frequency (the weighted frequency).

  3 and 4 show frequency weighting processing in the present embodiment. FIG. 3 shows a function of the weighted frequency, and the function of the weighted frequency represents the relationship between the original frequency (frequency before weighting) and the weighted frequency. FIG. 4 shows changes in the two-dimensional coordinate histogram due to weighting.

  As shown in FIGS. 3 and 4, in the present embodiment, when the original frequency is less than the first threshold value Th1, the weighted frequency is 0, and the frequency of the coordinates is excluded from the calculation target of the centroid position. The Thereby, it can be made hard to receive the influence of noise. When the original frequency is equal to or higher than the first threshold Th1 and equal to or lower than the second threshold, the weighted frequency is a value obtained by subtracting the first threshold Th1 from the original frequency. Further, when the original frequency is larger than the second threshold value Th2, the weighted frequency is uniformly Th2-Th1. Thus, by providing the upper limit value of the frequency and suppressing the frequency to the upper limit value or less, it is possible to reduce the degree of influence of the large area portion.

The coordinates of the representative point when performing the weighted average using the weighted frequency is (Wx1, Wy1). The representative point (Wx1, Wy1) is expressed by the following equation.
Wx1 = Σ [x · W (H (x, y))] / Σ [W (H (x, y))]
Wy1 = Σ [y · W (H (x, y))] / Σ [W (H (x, y))]
Where W (h) = 0 (h <Th1)
= h−Th1 (Th1 ≦ h ≦ Th2)
= Th2-Th1 (h> Th2)

  Here, W (h) is a function of the weighted frequency in FIG. By using the weighted frequency in this way, it is possible to obtain representative point coordinates that are not easily affected by a large area and are not easily affected by noise.

  As the weighted frequency function W (h), a function with finer divisions may be used, or a higher-order function, a look-up table, or the like may be used.

  Further, the threshold values Th1 and Th2 may be fixed values determined in advance. The threshold values Th1 and Th2 can also be determined adaptively from the feature quantity of the frequency H (x, y) of the two-dimensional coordinate histogram. Examples of the feature amount include parameters related to frequency distribution such as maximum value, minimum value, average value, and standard deviation of frequency. By determining the threshold values Th1 and Th2 according to the feature amount, the weighted frequency can be changed according to the feature amount.

For example, when the average value and the standard deviation are used as the feature amounts, the threshold values Th1 and Th2 can be obtained by the following expressions.
Th1 = mean value-a x standard deviation
Th2 = mean value + b x standard deviation

  Here, a and b are predetermined constants. By this process, the threshold values Th1 and Th2 can be changed according to the characteristics of the frequency distribution. In this example, the threshold values Th1 and Th2 increase as the average value increases. Further, as the standard deviation is larger, the threshold values Th1 and Th2 are farther from the average value. As a result, the upper limit is applied to the frequency in the appropriate range with the higher frequency in the frequency distribution, and the threshold value Th1 is set so that the frequency in the appropriate range with the lower frequency becomes zero. , Th2 is controlled.

Further, for example, when the maximum value and the minimum value are used as the feature amount, the threshold values Th1 and Th2 can be obtained by the following expressions.
Th1 = c × minimum value
Th2 = d × maximum value

  Here, c and d are predetermined constants. In this case, the threshold value Th1 can be set to an appropriate value that is larger than the minimum frequency and defined by the constant c in the frequency distribution. Further, the threshold value Th2 can be set to an appropriate value defined by a constant d smaller than the maximum frequency in the frequency distribution. Therefore, the upper limit is imposed on the frequency in the appropriate range with the higher frequency, and the threshold values Th1 and Th2 are controlled so that the frequency in the appropriate range with the lower frequency becomes zero.

For example, when using an average value as the feature amount, the threshold values Th1 and Th2 can be obtained by the following equations.
Th1 = e × average value
Th2 = f × average value

  Here, e and f are predetermined constants. In this case, on the basis of the average value, the threshold value Th1 can be set to an appropriate value that is smaller than the average value and defined by the constant e. Further, the threshold value Th2 can be set to an appropriate value that is larger than the average value and defined by the constant f. Accordingly, the upper limit is set for the frequency in the appropriate range with the higher frequency, and the threshold values Th1 and Th2 are controlled so that the frequency in the appropriate range with the lower frequency becomes zero. .

  In this way, in the present embodiment, the weighting frequency can be changed by controlling the threshold values Th1 and Th2 in accordance with the frequency distribution of the two-dimensional coordinate histogram. At this time, as in the above example, a frequency range including the maximum frequency is defined by the function of the frequency feature quantity (a function for obtaining the threshold value Th2), and the upper limit of the frequency is limited within this range. Further, a range including the minimum frequency is defined by the function of the feature amount (a function for obtaining the threshold value Th1), and the frequency of the range is set to zero. In this way, the upper limit can be set for the frequency in the appropriate range with the higher frequency, and the weight can be made variable so that the frequency in the appropriate range with the lower frequency is excluded from the weighted average target. The white balance can be adjusted with higher accuracy by suitably reducing the effects of noise and noise.

  As a modification of the present embodiment, a plurality of functions exemplified above can be combined.

  The process for obtaining the representative point coordinates has been described above. The representative point coordinates Wx1 and Wy1 obtained in this way are supplied to the gain adjustment unit 5, and the gain adjustment unit 5 performs white balance adjustment. Since the representative point coordinates Wx1, Wy1 are values of the B / G axis and the R / G axis, the reciprocal of these is the amount of gain for white balance adjustment. Therefore, the gain adjusting unit 5 performs processing for multiplying the B signal and the R signal by the reciprocals of Wx1 and Wy1 and leaving the G signal as it is, thereby adjusting the white balance. That is, when the gain of G is set to 1 time, the gain of B is G / B = 1 / Wx1, and the gain of R is G / R = 1 / Wy1. Then, the video signals R ′, G ′, B ′ after the white balance adjustment are output from the video signal processing device 1.

  The operation of the video signal processing apparatus 1 has been described above. Next, a modified example of the video signal processing apparatus 1 will be described.

  In the present embodiment, the video signal is an RGB signal. However, the present invention is not limited to this, and signals other than RGB may be used. For example, the present invention can be similarly applied to video signals Y, RY, BY, and the like.

  In the present embodiment, the representative point coordinates are the coordinates of the barycentric position of the coordinate signal group. However, the present invention is not limited to this. For example, the representative point coordinates may be the coordinates of the median value of the coordinate signal group. The median can be a median. For example, for each of the x coordinate and the y coordinate, a median value (coordinate having the middle rank) is obtained, and a combination thereof is used as the representative point coordinates.

  In the above description, the frequency for one screen is required. However, the achromatic region in the screen may be detected by image processing, and white balance adjustment may be performed based on the signal in the achromatic region. In this case, the RGB signal of the achromatic region is converted into a signal of a two-dimensional coordinate system, a two-dimensional coordinate histogram is created by the above-described processing, representative point coordinates are obtained, gain is determined from the representative point coordinates, This gain is added to the video signal of the entire screen.

  In the above description, the frequency for one screen is obtained. However, the screen may be divided into a plurality of parts, the frequency may be obtained for each region, and the weighted frequency may be further changed for each region.

  The video signal processing apparatus 1 according to the first embodiment of the present invention has been described above. According to this embodiment, a video signal is converted into a coordinate signal of a two-dimensional coordinate system indicating color information, a frequency of the coordinate signal is calculated, a two-dimensional coordinate histogram is obtained, and a representative of the two-dimensional coordinate system histogram is obtained. Point coordinates are obtained, and white balance adjustment is performed using the representative point coordinates. As described above, the video signal is converted into the coordinate signal of the two-dimensional coordinate system of the color information, and then the white balance adjustment is performed using the representative point coordinates of the coordinate signal group, thereby performing the highly accurate white balance adjustment. be able to.

  In this regard, in the prior art, RGB signals are first integrated to obtain an average value, and a white balance gain is determined from the ratio of the average values. Unlike such a conventional technique, in the present embodiment, the ratio of the average values is not calculated. In this embodiment, first, ratio values such as R / G and B / G are calculated, a representative value of the ratio (representative point coordinates) is obtained from the frequency of the ratio, and a gain is determined from the representative value of the ratio. The Due to such differences, according to the present embodiment, the accuracy of white balance adjustment can be improved.

  Further, according to the present embodiment, the two axes of the two-dimensional coordinate system are blue / green and red / green, blue / luminance and red / luminance, or (blue-green) / luminance and (red). -Green) / luminance, or (blue-luminance) / luminance and (red-luminance) / luminance (in the main example above, the two axes are blue / green and red / green). As a result, the luminance component in the coordinate signal of the two-dimensional coordinate system is reduced, and a histogram is created from such a coordinate signal to perform white balance adjustment. Accordingly, highly accurate white balance adjustment with reduced influence of the luminance level can be performed.

  Further, according to the present embodiment, the coordinates of the centroid position of the coordinate signal group are obtained by weighted averaging using the frequency of the two-dimensional coordinate histogram, and the coordinates of the centroid position are set as the representative point coordinates. Thereby, it is possible to obtain appropriate representative point coordinates representing the coordinate signal group obtained from the video.

  Further, according to the present embodiment, as described with reference to FIGS. 3 and 4, the weighting is performed by weighting the frequency of the coordinate signal at each position in the two-dimensional coordinate system according to the frequency. Frequency is required. Then, the barycentric position of the coordinate signal group is obtained by a weighted average using the weighted frequency. Since weighting according to the frequency is performed, the influence of a subject with a large area can be reduced, and high-precision white balance adjustment can be performed.

  Further, according to the present embodiment, as described with reference to FIGS. 3 and 4, the weighting is performed so that the frequency of the coordinate signal at each position in the two-dimensional coordinate system is equal to or less than the frequency upper limit value. As a result, the frequency of the coordinate signal is limited to a frequency upper limit value or less, so that the influence of a subject with a large area can be reduced and highly accurate white balance adjustment can be performed.

  Further, according to the present embodiment, as described with reference to FIGS. 3 and 4, when the frequency of the coordinate signal at each position in the two-dimensional coordinate system is equal to or lower than the frequency lower limit value, the frequency is excluded from the weighted average target. Weighting is performed as follows. In the above example, the frequency is set to zero. As a result, coordinate signals with a low frequency can be excluded from the calculation target of the weighted average, the influence of noise can be reduced, and highly accurate white balance adjustment can be performed.

  Further, according to the present embodiment, the weighted frequency changes according to the feature amount representing the feature of the two-dimensional coordinate histogram. The feature amount is at least one of a maximum value of frequency, a minimum value of frequency, an average value of frequency, and a standard deviation of frequency. In the above description, the threshold value of the function of the weighted frequency is variably set according to the feature amount, and the weighted frequency changes accordingly. By such processing, the weighting frequency can be adjusted appropriately according to the feature amount of the two-dimensional coordinate histogram, and high-accuracy white balance adjustment can be performed with less influence of area and noise.

  Next, a video signal processing apparatus according to a second embodiment of the present invention is shown in FIG.

  The video signal processing apparatus 10 of the second embodiment shown in FIG. 5 has a configuration in which a coordinate position weighting unit 6 is added to the video signal processing apparatus 1 of the first embodiment shown in FIG. Yes. The coordinate position weighting unit 6 functions as a part of the representative point coordinate calculation unit 4 and is configured to weight the frequency of the coordinate signal according to the coordinate position. Hereinafter, description of the same matters as in the first embodiment will be omitted, and the second embodiment will be described focusing on the differences from the first embodiment.

  The coordinate position weighting unit 6 outputs a coordinate weight coefficient Z (x, y) corresponding to the coordinate position. In this embodiment, the coordinate weighting coefficient Z (x, y) of each coordinate is stored in advance, and this coordinate weighting coefficient Z (x, y) is read and output. The coordinate weight coefficient Z (x, y) may be stored in the form of a table.

The representative point coordinate calculation unit 4 obtains representative point coordinates using the frequency of weighting using the coordinate weighting coefficient Z (x, y). More specifically, the representative point coordinate calculation unit 4 first weights according to the magnitude of the frequency H (x, y) output from the histogram calculation unit 3 as described in the first embodiment. The weighted frequency W (H (x, y)) is obtained. Further, the representative point coordinate calculation unit 4 multiplies the weighted frequency W (H (x, y)) by the coordinate weighting coefficient Z (x, y), thereby adding a weight according to the coordinate position. Find the weighted frequency. Then, representative point coordinates are obtained by a weighted average using the weighted frequency. The representative point coordinates of this embodiment are (Wx2, Wy2). The representative point coordinates (Wx2, Wy2) are expressed by the following formula.
Wx2 = Σ [x • W (H (x, y)) • Z (x, y)] / Σ [W (H (x, y)) • Z (x, y)]
Wy2 = Σ [y ・ W (H (x, y)) ・ Z (x, y)] / Σ [W (H (x, y)) ・ Z (x, y)]

  Next, how to determine the coordinate weight coefficient Z (x, y) will be described. Two-dimensional coordinates (x, y) are measured when a wide variety of achromatic and chromatic subjects are imaged with various light sources in advance. Based on the measurement result, a large value is set for the coordinate weight coefficient Z (x, y) in the coordinates obtained from the achromatic object and in the vicinity thereof. Further, a coordinate weight coefficient Z (x, y) small value is set in the coordinates measured by imaging chromatic colors and in the vicinity thereof. By setting the coordinate weighting coefficient Z (x, y) in this way, the specific gravity of the achromatic color part can be increased, so that representative point coordinates with little influence of the chromatic color in the subject can be obtained.

  As an example, the two-dimensional coordinate system is divided into two types of areas, an achromatic color area and a chromatic color area. The achromatic color region is an achromatic color and its vicinity, and the chromatic color region is a chromatic color and its vicinity. A coordinate weighting factor Z1 is set for the achromatic color region, and a coordinate weighting factor Z2 is set for the chromatic color region. At the coordinates (x1, y1) of the achromatic region, the frequency W (H (x1, y1)) is multiplied by Z1. Further, at the coordinates (x2, y2) of the chromatic color region, the frequency W (H (x2, y2)) is multiplied by Z2. Such processing is performed, and the representative point coordinates are obtained. The coordinate weight coefficient is not limited to the above. The coordinate weight coefficient may be set more finely at a plurality of stages.

  The video signal processing apparatus 10 according to the second embodiment of the present invention has been described above. According to the present embodiment, the weighted frequency obtained by weighting the frequency of the coordinate signal at each position in the two-dimensional coordinate system according to the coordinate position of the coordinate signal is obtained. Then, the barycentric position of the coordinate signal group is obtained by a weighted average using the weighted frequency. Thereby, it is possible to perform highly accurate white balance adjustment that reduces the influence of the area and the luminance level while reducing the influence of the chromatic color.

  In addition, according to the present embodiment, when calculating the weighted frequency according to the coordinate position, the coordinates of the achromatic color region in the two-dimensional coordinate system and the coordinates located in the vicinity thereof are coordinates in the chromatic color region. It is set higher than the weight of. Thereby, it is possible to perform highly accurate white balance adjustment that reduces the influence of the area and the luminance level while reducing the influence of the chromatic color.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and it goes without saying that those skilled in the art can modify the above-described embodiments within the scope of the present invention.

  As described above, the video signal processing apparatus according to the present invention has the effect of being able to perform highly accurate white balance adjustment that is not easily affected by the area and luminance level of the subject, and automatically adjusts the white balance of electronic cameras, video cameras, and the like. It is useful as a video signal processing device to be adjusted.

1 is a block diagram of a video signal processing apparatus according to a first embodiment of the present invention. The figure which shows the two-dimensional coordinate histogram calculated by a histogram calculation process The figure which shows the example of the function of the weighted frequency used for representative point coordinate calculation The figure which shows the change of the two-dimensional coordinate histogram by weighting The block diagram of the video signal processing apparatus in the 2nd Embodiment of this invention The figure which shows the color signal ratio characteristic curve used by the white balance adjustment process in the conventional video signal processing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 10 Video signal processing apparatus 2 Two-dimensional coordinate conversion part 3 Histogram calculation part 4 Representative point coordinate calculation part 5 Gain adjustment part 6 Coordinate position weighting part

Claims (9)

Two-dimensional coordinate conversion means for converting a video signal into a coordinate signal of a two-dimensional coordinate system indicating color information, and histogram calculation for obtaining a two-dimensional coordinate histogram by calculating the frequency of the coordinate signal in the two-dimensional coordinate system A representative point coordinate calculating means for obtaining a representative point coordinate representing the coordinate signal group obtained by the two-dimensional coordinate conversion means according to the frequency of the two-dimensional coordinate histogram, and a white point based on the representative point coordinate. A video signal processing device having a gain adjustment means for performing balance adjustment ,
The representative point coordinate calculation means includes:
The weighted frequency obtained by weighting the frequency of the coordinate signal at each position of the two-dimensional coordinate system according to the magnitude of the frequency is obtained, and the barycentric position of the coordinate signal group by the weighted average using the weighted frequency And the coordinates of the barycentric position as the representative point coordinates,
The weighted frequency is configured to change according to a feature amount representing a feature of the two-dimensional coordinate histogram, and the feature amount includes a maximum value of the frequency, a minimum value of the frequency, an average value of the frequency, and the A video signal processing device that is at least one of the standard deviations of the frequency . The video signal processing apparatus according to claim 1 , wherein the representative point coordinate calculation unit performs weighting so that the frequency of the coordinate signal at each position in the two-dimensional coordinate system is equal to or less than a frequency upper limit value. The representative point coordinate calculation means according to claim 1 for weighting so that the frequency of said coordinate signal at each position in the two-dimensional coordinate system to exclude the frequency if: the frequency lower limit value from the weighted average target Video signal processing device. The representative point coordinate calculation means obtains a weighted frequency obtained by weighting the frequency of the coordinate signal at each position of the two-dimensional coordinate system according to the coordinate position of the coordinate signal, and uses the weighted frequency. The video signal processing apparatus according to claim 1 , wherein a gravity center position of the coordinate signal group is obtained by a weighted average. When calculating the weighted frequency according to the coordinate position, the representative point coordinate calculating means calculates the weights of the coordinates located in the two-dimensional coordinate system and the coordinates located in the vicinity thereof in the coordinates located in the chromatic color area. The video signal processing apparatus according to claim 4 , wherein the video signal processing apparatus is set higher than the weight. Conversion from a video signal to a coordinate signal of a two-dimensional coordinate system indicating color information, calculating a frequency of the coordinate signal in the two-dimensional coordinate system to obtain a two-dimensional coordinate histogram, and the frequency of the two-dimensional coordinate histogram In accordance with the video signal processing method, a representative point coordinate representing a coordinate signal group converted from the video signal is obtained, and white balance adjustment is performed based on the representative point coordinate .
The calculation of the representative point coordinates is as follows:
A weighted frequency obtained by weighting the frequency of the coordinate signal of the two-dimensional coordinate system according to the magnitude of the frequency is obtained, and then the barycentric position of the coordinate signal group is obtained by a weighted average using the weighted frequency. And the coordinates of the center of gravity position are calculated as the representative point coordinates, and the weighted frequency is calculated from the maximum value, minimum value, average value, and standard deviation of the frequency of the coordinate signal of the two-dimensional coordinate system. A video signal processing method that changes according to at least one . Two-dimensional coordinate conversion means for converting a video signal into a coordinate signal of a two-dimensional coordinate system of color information, histogram calculation means for obtaining a two-dimensional coordinate histogram of the appearance frequency of the coordinate signal, and the frequency of the two-dimensional coordinate histogram Video signal processing comprising: representative point coordinate calculating means for obtaining representative point coordinates of the coordinate signal group obtained by the two-dimensional coordinate conversion means; and gain adjusting means for performing white balance adjustment based on the representative point coordinates. A device,
The representative point coordinate calculation means includes:
For the frequency of the two-dimensional coordinate histogram, the coordinates of the center of gravity position of the coordinate signal group are calculated as the representative point coordinates by a weighted average using a weighted frequency weighted according to the magnitude of the frequency, and A video signal processing apparatus that changes the weighted frequency according to a characteristic of a frequency distribution of the two-dimensional coordinate histogram . The video signal processing apparatus according to claim 7, wherein the frequency distribution feature of the two-dimensional coordinate histogram is at least one of a maximum value, a minimum value, an average value, and a standard deviation of the frequency of the two-dimensional coordinate histogram . A video signal is converted into a coordinate signal of a two-dimensional coordinate system of color information, a two-dimensional coordinate histogram of the appearance frequency of the coordinate signal is obtained, and the representative point coordinates of the coordinate signal group are determined according to the frequency of the two-dimensional coordinate histogram. A video signal processing method for calculating and white balance adjustment based on the representative point coordinates,
The calculation of the representative point coordinates is as follows:
A weighted frequency obtained by weighting the frequency of the coordinate signal of the two-dimensional coordinate system according to the magnitude of the frequency is obtained, and then the barycentric position of the coordinate signal group is obtained by a weighted average using the weighted frequency. And the coordinates of the center of gravity position are calculated as the representative point coordinates,
A video signal processing method for changing the weighted frequency according to at least one of a maximum value, a minimum value, an average value, and a standard deviation of the frequency of the coordinate signal of the two-dimensional coordinate system .

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