JPH0646449A - Achromatic processing method for image data - Google Patents

Abstract

PURPOSE:To eliminate the leakage of a sample color at a boundary part of synthesization and to obtain a soft chromakey synthetic screen with high quality by applying the continuous achromatic processing to the mixture component of the sample color and another color. CONSTITUTION:The foreground picture data are fetched into an image memory 1 and the hue data, etc., on the images are read out of the memory 1. A CPU 4 generates a parameter necessary for the achromatic processing conversion of a hue range (processing range) where the achromatic processing is carried out based on the read data. The parameter is sent to a conversion processing part 2. The part 2 performs the achromatic processing of the foreground picture data read out of the memory 1 through an arithmetic circuit based on the parameter received from the CPU 4 and a look-up table. Thus the automatic ground picture data are obtained. The processing range of the part 2 is set by the CPU 4 with software in accordance with the hue distribution of the mixed color set at the boundary part of different colors and therefore never limited by the shape and the size of the processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an achromatic processing method of image data used for soft chroma key screen composition.

[0002]

SUMMARY OF THE INVENTION The present invention provides a composite image quality due to discontinuity of processing that occurs at a boundary portion where a sampling color (chroma key blue) and other colors are mixed in an achromatic processing of image data used for soft chroma key screen composition. For the purpose of improving the deterioration, obtain the hue distribution of the mixed color based on the image data, set the hue range to perform the achromatic processing by adapting to this hue distribution, and for the mixed color data within this set hue range The achromatic process is continuously performed.

[0003]

2. Description of the Related Art First, soft chroma key screen composition and color erasing processing will be described.

In soft chroma key screen synthesis, a foreground image and a background image are synthesized by a linear key generated from the level of the extracted color (chroma key blue). At this time, since the foreground image and the background image are mixed and combined at the boundary portion of the combined image, the extracted color remains and remains, and blue spots are generated to deteriorate the image quality. As a solution to this blue spot, in the soft chroma key screen composition, as shown in FIG. 2, in the key generation / achromatization processing unit 21, an achromatization processing for removing the extracted color component from the foreground image is performed, and the achromatization processing is performed. A foreground picture is obtained and a key signal is generated from the foreground picture. Then, the synthesizing unit 22 synthesizes the foreground image and the background image that have been subjected to the achromatization using the key signal to obtain a synthesized image.

As an example of such conventional soft chroma key screen synthesis, there is "Level adaptive digital RGB chroma key" (NHK Giken monthly report, February 1988 issue), and the achromatic processing method applied to the chroma key is used. As shown in FIG. As shown in FIG. 3, within a fan-shaped hue range having an achromatic color centered on the hue of the extracted color E (arrow 31,
The color component (denoted by numeral 32) is modulated by a carrier having a phase opposite to that of the wiped color component at the level of the linear key, and is added to the foreground image to perform the achromatization process.

[0006]

Generally, there are a plurality of objects of different colors on the screen. At this time, due to blurring of the camera, reflection of colors, and the like, colors are mixed at the boundaries of the respective objects in the screen. For example, in the extracted color B as shown in FIG. 4A, A color, B color,
Considering a foreground image with C-color and D-color objects, there is a mixed color portion at the boundary between the objects. At this time, on the hue plane, mixed color components are continuously distributed between colors A and B, between colors B and C, and between colors B and D, as shown in FIG. 4B.

As shown in FIG. 3, in the conventional achromatic processing method, the fan-shaped hue range including the extracted color is set as the processing range. Therefore, in the case where the mixed color is widely present on the hue plane as shown in FIG. 4B, the achromatization cannot completely deal with the mixed color. In other words, in order to cover the mixed colors, the central angle of the fan shape must be increased, but if this is the case, the color components that should not be erased, which are not in contact with the extracted colors, will also be processed. Therefore, the composite image quality deteriorates. Therefore,
In the conventional achromatic processing method, as shown in FIG. 5, the boundary of the processing range (indicated by arrows 33 and 34 in the drawing) must be crossed in the mixed color component, and the achromatic processing is performed even in the mixed color. The components that are not the components are clearly separated. As described above, in the conventional achromatization process, only the discontinuous process can be performed on the mixed color continuously distributed between the extracted color and the other color, and the leakage of the extracted color cannot be eliminated.

As described above, the conventional fan-shaped processing range method has a drawback that it cannot sufficiently process mixed colors.

Therefore, an object of the present invention is to provide an achromatic processing method for image data that solves the above problems.

[0010]

In order to achieve the above object, the present invention is based on image data used for soft chroma key screen synthesis, and based on image data, the hue distribution of the mixed color at the boundary where the extracted color and other colors are mixed. Is obtained, a hue range for performing the achromatic processing is set in accordance with the hue distribution, and the achromatic processing is continuously performed on the mixed color data within the hue range of the image data.

[0011]

According to the present invention, the hue range in which the achromatic processing is performed is set to a range adapted to the distribution of the mixed color, and the achromatic processing is performed on the mixed color.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a circuit of an achromatic processing unit according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 is an image memory for fetching foreground image data, and 2 is a conversion processing unit for performing an achromatization process and the like, and has a look-up table and an arithmetic circuit.
Reference numeral 3 is a bus, and 4 is a CPU that controls the image memory 1 and the conversion processing unit 2 via the bus 3. Reference numeral 5 is a key generator that generates a key signal from the foreground image data. The flow of processing will be described with reference to FIG. First, the foreground image data is loaded into the image memory 1, and the data such as the hue of the image in the foreground image data is read therefrom. The CPU 4 generates, from the read data, parameters necessary for achromatic processing conversion, such as a hue range (processing range) for achromatic processing,
It is sent to the conversion processing unit 2. The conversion processing unit 2 uses the parameters from the CPU 4 to refer to the look-up table and perform an achromatization process on the foreground image data from the image memory 1 by an arithmetic circuit.

Next, the setting of the processing range in the conversion processing unit 2 will be described. In the present invention, the processing range is set by software by the CPU 4 in accordance with the hue distribution of the mixed color at the boundary of different colors, so the shape and size of the range are not limited. FIG. 6 shows an example of range setting. In this example, A color and B color, B color and C color, B color and D
The range in which the color erasing process is performed is set according to the distribution shape of each color mixture. Therefore, the mixed color of the extracted color B and other colors is included in the processing range, and the achromatizing process can be continuously performed in the conversion processing unit 2.

Next, an example of continuous achromatic processing in the conversion processing unit 2 for mixed colors within the processing range obtained as described above will be given. The achromatic processing may be continuous, and the processing method is not limited, but FIG. 7 shows an example of linearly proportional processing. The relationships in this figure are set in a lookup table. In FIG. 7, it is assumed that the color A is unprocessed and the color B is erased, that is, converted to an achromatic color (O color). At this time, Z on the A-B straight line
The color is converted to the Z'color on the AO line. The positional relationship of the intermediate color (Z color) with respect to A color and B color on the A-B straight line is the same as that of the intermediate color (Z 'color) on the A-O straight line.
It is saved in the positional relationship for color and O color. In other words, when expressed by the formula, it becomes as follows,

[0017]

[Equation 1]

Of the image data input to the conversion processing unit 2, the arithmetic circuit refers to the look-up table to perform continuous achromatization on the corresponding data to obtain achromatic foreground image data. It will be.

[0019]

According to the present invention, in soft chroma key screen compositing, leakage of the extracted color at the boundary of composition is eliminated by continuously performing the achromatization process of the mixed color components of the extracted color and other colors. It is possible to obtain a high quality soft chroma key composite screen.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an achromatic processing unit according to the present invention.

FIG. 2 is a conceptual diagram of soft chroma key composition, which is provided as a reference.

FIG. 3 is a diagram showing a conventional achromatic processing method.

4A is a diagram showing an example of a general image in which an object of a plurality of colors is present, and FIG. 4B is a hue plan view thereof.

5 is a diagram showing a case where an achromatic processing range is set for an image as shown in FIG. 4 by a conventional method.

FIG. 6 is a diagram showing a case where an achromatic processing range is set for an image as shown in FIG. 4 according to the present invention.

FIG. 7 is a diagram showing an example of continuous achromatic processing according to the present invention.

[Explanation of symbols]

 1 image memory 2 conversion processing unit 3 bus 4 CPU 5 key generation unit

Claims (1)

[Claims] 1. A hue distribution of a mixed color at a boundary portion where the extracted color and another color are mixed is obtained based on image data used for soft chroma key screen composition, and an achromatizing process is applied to the hue distribution. An achromatic processing method for image data, characterized in that a hue range for performing the above is set, and the achromatic processing is continuously performed on the mixed color data within the hue range of the image data.