JP3085971B2 - Hue detector for color image signal - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting a hue of a color image signal, and more particularly to a hue detection device suitable for generating a chroma key signal.

[Summary of the Invention]

The chroma key signal is a signal indicating that a specific color signal component has appeared at a predetermined level or more in a color image signal, and is useful for special effect processing such as extraction or insertion of a specific portion on an image plane. Conventionally, the types of color signal components that are the generation conditions are R (red), G (green), and B (blue).
Colors or their complementary colors, such as Ma (magenta), Cy (cyan), and Ye (yellow), are based on fairly rough classifications, and are not satisfactory in terms of fine grained processing. .

According to the present invention, three colors of red, green and blue constituting a color video signal are provided.
Focusing on the fact that the hue can be determined based on the combination of the levels of the types of color signal components and the level ratio, an arbitrary hue can be continuously detected within the hue.

[Conventional technology]

For image processing according to the hue of the color image signal,
Conventionally, a technique using a chroma key signal is known.

A conventional example of the chroma key technique will be described with reference to FIG. 10. In FIG. 10, reference numerals 5, 6, and 7 denote amplifiers, 8 denotes an adder circuit, and 9 denotes a comparator.

First, the amplifiers 5 to 7 respectively output an R signal, a G signal, and a B signal.
It functions to amplify the signal to a predetermined level, and to provide a predetermined gain to the input signal by gain control signals of R gain, G gain, and B gain, respectively. , B gain can be amplified only by a specific hue.

For example, if the R gain is Gr, the G gain is Gg, and the B gain is Gb, Gr = cosφ Gg = cos (φ−4 / 3π) Gb = cos (φ−2 / 3π) Is set in the range of 0 to 2π, it is possible to arbitrarily amplify only a specific hue for all hues with reference to R.

Outputs of these amplifiers 5 to 7 are input to an adding circuit 8. Therefore, assuming that the output of the adder circuit 8 is Y, the output Y is Y = Rcosφ + Gcos (φ−4 / 3π) + Bcos (φ−2 / 3π).

Then, in order to change the hue of the color image signal by R, G and B, R = cos θ G = cos (θ−4 / 3π) B = cos (θ−2 / 3π) θ: 0 to 2π Then, Y = cos θ−0.5 × {cos (θ−4 / 3π) + cos (θ−2 / 3π)} = 1.5 cos θ Therefore, the maximum output Y is θ = 0,
2π, that is, when the hue becomes R. Considering this by a general formula, Y = cosθ · cosφ + cos (θ−2 / 3π) · cos (φ−2 / 3π) + cos (θ−4 / 3π) ·
cos (φ−4 / 3π).

Therefore, θ when the output Y in this general formula is maximized
Is obtained by dY / dθ = 0, tanθ = tan
φ, and finally θ = φ.

Therefore, the hue having φ as the set angle is amplified to the maximum level.

The output Y of the adding circuit 8 is input to a comparator 9, where it is compared with a predetermined level, and an output key is generated in response to an input signal exceeding this level.

Therefore, looking at the output Key of the comparator 9, it is a signal that becomes positive only when the hue of the color image signal by the RGB input is in the vicinity of the set angle φ. Therefore, the desired chroma key signal is Will be obtained.

[Problems to be solved by the invention]

The above-mentioned prior art does not consider the hue of the color image signal, and has a problem that it is difficult to perform the image processing by judging the hue in detail. Was.

In other words, the chroma key signal in the above-mentioned prior art is merely a signal indicating whether or not the hue of the color image signal has become a specific hue, and thereafter, the content of the hue cannot be finely determined. is there.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the related art, and has as its object to provide a color image capable of detecting a hue of a color image signal in detail and generating a chroma key signal of an arbitrary hue. An object of the present invention is to provide a signal hue detection device.

In the prior art, if a device for generating each chroma key signal is provided in correspondence with a plurality of types of hues, it is possible to cope with this, but the circuit scale increases in proportion to the increase in the types of hues. Nevertheless, it is only possible to judge discrete hues, and it is not possible to determine the type of hue at any continuous point as in the present invention.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a means for determining a hue region by a combination of a color signal component having a maximum level and a color signal component having a second level among three types of color signal components; The value obtained by subtracting the level value of the color signal component having the second level from the level value of the color signal component having the maximum level is defined as the primary color component level value.
The value obtained by subtracting the level value of the color signal component having the minimum level from the level value of the color signal component having the second level is set as a complementary color component level value, and the level of the primary color component level value and the complementary color component level value is determined. A means for calculating the hue angle by the ratio is provided.

[Action]

First, the hue area of the input signal is determined by the means for determining the hue area, and the hue angle within this hue area is determined by the means for calculating the hue angle, so that it is possible to determine any hue. Become.

〔Example〕

Hereinafter, a hue detecting device for a color image signal according to the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 shows an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a hue region determination unit, 2 denotes a ratio calculation unit, 3 denotes a hue angle calculation unit, and 4 denotes a hue determination unit. Reference numeral 10 denotes the entire hue detection device.

The hue region determination unit 1 is configured to output RGB signals constituting a color video signal.
Are input, and the levels of these color signals are detected. Then, by the combination of the type of the color signal having the maximum level and the type of the color signal having the second level, the hue of the currently input color video signal is
It is determined which of the six types of hue regions shown in the chart of FIG. That is, the type of the color signal having the maximum level and the type of the color signal having the second level among the three types of RGB color signals are detected.
Six types of combinations consisting of the same primary color as the color signal having the maximum level and the complementary colors sandwiched between the color signal having the maximum level and the color signal having the second level, that is,
(R: Ma), (B: Ma), (B: Cy), (G: Cy), (G: Ye),
(R: Ma), and from the detection results of these levels, it can be determined which of the hue regions in FIG. 2 exists.

First, the color signal having the maximum level and the color signal having the second level are detected. Assuming that the level relationship of the color signals at this time is as shown in FIG. 3, the color signal having the maximum level is R
And the color signal having the second level is G.

Next, the table of FIG. 4 is searched based on the detection result. Then, at this time, as described above,
Since the color signal having the highest level is R and the color signal having the second level is G, these level relations are expressed as R>
G> B, which corresponds to the second from the bottom of the table in FIG. 4, and the hue area of the input signal at this time is the area 6 in FIG.

Subsequently, the hue region determination unit 1 subtracts the level value of the color signal having the second level from the level value of the color signal having the maximum level, and subtracts the subtracted value as shown in FIG. Similarly, the level value of the color signal having the minimum level is subtracted from the level value of the color signal having the second level, and the subtracted value is calculated as shown in FIG. And

In addition, in the determination of the hue region based on the above table,
Although the level value of the color signal having the minimum level is not necessary,
Since it is necessary for calculating the complementary color component, it is described in the table of FIG.

In this way, the hue area determination unit 1 outputs the determination result of the hue area (the area 6 in this case), the primary color component level at this time, and the complementary color component level.

Next, the ratio calculating unit 2 inputs the above-described primary color component level and complementary color component level, and calculates a ratio between the two.

First, the larger of the primary color component level and the complementary color component level is the divisor (denominator), and the smaller one is the dividend (numerator).
And perform division. In the case of an image consisting of only white components, both components are at the 0 level.
For example, a flag may be set to notify that there is no color component.

Now, assuming that the primary color component level> the complementary color component level, the dividend (numerator) = complementary color component level = A, the divisor (denominator) = primary color component level = B, and the ratio K = A / B, as shown in FIG. Angle θ
Is obtained by the following equation.

Therefore, when the ratio K is calculated by the ratio calculator 2, the result is input to the hue angle calculator 3, where the angle θ is calculated by the above equation. Since this operation is very difficult to perform in a digital circuit, it is performed by a conversion process based on a table search. That is, in this conversion process, .theta. Is calculated in advance for various values of K, tabulated, and thereafter, a search is performed using the value of K, and .theta. Is output. For example, when K = 0.3, θ = 12.73 °, and if 0.3 is searched, 12.73 ° may be output.

The hue determination unit 4 receives the area information from the hue area determination unit 1 and the hue angle θ from the hue angle calculation unit 3 and generates an output representing the angle of deviation from the reference hue based on these. .

Accordingly, from the hue determination unit 4, data indicating in which region in the chart of FIG. 2 the hue of the color image signal at that time is located, and a reference hue in this region, for example, In the example shown in FIG. 3, data representing the angle between the R and Ma directions is obtained. Therefore, according to this embodiment, the hue information expressed as a numerical value can be easily obtained. Can be obtained.

As described above, in the above embodiment, since the hue information expressed as a numerical value is output from the hue determination unit 4, data representing the hue to be used as a key is prepared, and this data and the hue determination unit are prepared. By comparing the data output from the data No. 4 and extracting the output when they match, it is possible to easily obtain a chroma key signal having an arbitrary hue direction on the chart of FIG.

FIG. 6 shows an application example of the present invention, in which the present invention is applied to a contour emphasizing circuit.

In FIG. 6, reference numeral 10 denotes a hue detection device according to the present invention, which has, for example, the configuration shown in FIG.

Reference numeral 20 denotes an outline emphasis signal generation circuit which functions to detect a changed portion of the RGB signal and generate a predetermined outline emphasis signal.

Reference numeral 30 denotes a gain control signal generation circuit which sets the hue obtained by the hue detection device 10 to (θ), and converts the hue (θ) into a contour emphasis signal gain characteristic control signal g (θ).
It may be constituted by a digital circuit or a memory.

7, 8, and 9 show examples of the characteristics of the control signal g (θ).

Numeral 40 denotes a multiplication circuit which takes the product of the above-mentioned edge enhancement signal and gain control signal, and has the function of inputting the multiplication result to adders 50, 60 and 70.

Therefore, considering the case of the R signal, assuming that the contour emphasis signal is E _R , the R signal is emphasized as R + E _R × g (θ).

When the gain control signal g (θ) has the characteristics shown in FIG. 7, the R, G, and B signals supplied from the video signal input are the signals whose hues are set to B in the gain control signal generation circuit 30.
When a predetermined range centered on (blue) is reached, the adder 50
The outline emphasis signal added via the lines 70 to 70 is made almost zero, and a video signal output whose outline is emphasized according to the hue can be obtained.

As described above, according to the present invention, it is possible to perform control in which hue is specified in detail, and it is possible to easily perform advanced image processing.

〔The invention's effect〕

According to the present invention, the hue of a color image signal can be accurately determined from among consecutive hues, so that fine-grained image processing according to the hue can be performed. For example, when giving a video signal a gain characteristic corresponding to hue,
By combining the conversion memory with the present invention and writing desired characteristics in this memory, it is possible to obtain effects such as enabling fine-grained image processing corresponding to the hue.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a color image signal hue detecting device according to the present invention, FIG. 2 is an explanatory diagram of a hue region chart, FIG. 3 is an explanatory diagram showing an operation principle of the present invention, and FIG. FIG. 5 is an explanatory diagram showing an embodiment of a table for determining a hue region, FIG. 5 is a vector diagram for explaining operation, FIG. 6 is a block diagram showing an example of an outline emphasizing circuit which is an application example of the present invention,
7, 8, and 9 are characteristic diagrams, and FIG. 10 is a block diagram showing a conventional example of a hue detection device. DESCRIPTION OF SYMBOLS 1 ... Hue area determination part, 2 ... Ratio calculation part, 3 ... Hue angle calculation part, 4 ... Hue determination part, 10 ... Hue detection device.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 9/44-9/78 H04N 1/40-1/64

Claims (1)

(57) [Claims] In a video signal processing system for independently inputting and processing three types of color signal components constituting a color video signal, respective levels of the three types of color signal components are determined, and among them, a maximum is determined. Hue area determination means for determining a hue area based on a combination of a color signal component having the second level and a color signal component having the second level; and determining the second level from the level value of the color signal component having the maximum level. The value obtained by subtracting the level value of the color signal component having the minimum level is defined as the primary color component level value, and the value obtained by subtracting the level value of the color signal component having the minimum level from the level value of the color signal component having the second level is a complementary color component. Hue angle calculating means for calculating a hue angle based on the level ratio between the primary color component level value and the complementary color component level value, and determining the hue area by the hue area determining means. Result hue detection unit of the color image signal, characterized by being configured to detect hue by calculating the result of the hue angle calculating means.