JPH0465991A - Chroma key device - Google Patents

Abstract

PURPOSE:To cancel the variations of the darkness or the hue due to a stain, etc., of a backscreen to a foreground image by multiplying a signal subtracting a foreground image signal from a background image signal by the inversion signal of a key signal to be added with the foreground image signal. CONSTITUTION:A key signal K is transmitted to a multiplier 18, multiplied with an input signal of a variable level, and only the part of the object of the foreground image is taken out. The output signal from this multiplier 18 is turned to be a foreground image signal F3 by transmitted to an adder 16 and added with the output signal from the multiplier 15. A substracter 22 subtracts the signal F3 from a background image signal B1, and the output signal from the subtracter 22 is transmitted to an multiplier 23 to be multiplied with the inversion key signal from an inverter 17. This multiplication signal B3 is transmitted to an adder 14. The adder 14 addes an image signal F2 and the signal F3 after hue control processing, and a signal B4 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a chroma key device, and particularly to a chroma key device that superimposes and synthesizes a foreground image signal on a background image signal.

[Summary of the invention]

The present invention provides a ROMA key device that superimposes and synthesizes a foreground image signal and a background image signal. By multiplying and adding the multiplied signal and the foreground image signal, the output image is prevented from being adversely affected by dirt on the back screen of the foreground image.

[Conventional technology]

A chromakey device uses an image obtained by placing a subject, such as a person or object, in front of a screen with a predetermined back color (generally blue) as the foreground image, and then converts the hack-colored portion of this foreground image into a landscape image, etc. This will replace the background image. This chroma key device includes one that obtains a composite image by switching and selecting a foreground image and a background image according to a key signal obtained from a foreground image signal, and one that obtains a composite image by switching and selecting a foreground image and a background image according to a key signal obtained from a foreground image signal, and one that obtains a composite image by switching between a foreground image signal and a background image signal that have undergone predetermined signal processing. It is known to obtain a composite image by adding the

FIG. 4 shows a conventional example of the latter chromakey device.

That is, in this FIG. 4, three input terminals 41y
, 411, 419, the luminance signal (Y signal) of the foreground image
and two color signals (1 and Q signals) are respectively supplied,
The signal is sent to a key signal generation and hue suppression circuit 42. This circuit 42 outputs an output signal (
Y signal and ISQ signal) are sent to a cog (eg, NTSC coder) 43, and a key signal (K) is extracted based on the manually input foreground image signal.

The foreground image signal from Korg 43 is sent to adder 44. On the other hand, the background image signal supplied to the input terminal 45 is sent to a subtracter 46, and the output signal from the KOG 47 is subtracted therefrom. This Korg 47 is R (red), G (green)
, B (blue), and outputs a signal with a constant value that displays the bank color (usually blue) of the foreground image as, for example, an NTSC composite color video signal. . Therefore, the output signal from the subtracter 46 is obtained by subtracting the back color component signal from the background image signal. This subtracted output signal is sent to the multiplier 48 and multiplied by the key signal (K), thereby obtaining a background image signal from which the subject portion of the foreground image has been removed. This multiplication output signal is sent to the adder 44 and added to the foreground image signal, so that from the output terminal 49,
A signal of an image in which the background color portion of the foreground image is replaced by the background image is extracted.

[Problem to be solved by the invention]

By the way, in such a conventional chromakey device,
If the color of the back screen of the foreground image is not uniform, for example, if the level of the back color changes due to uneven lighting or dirt on the screen, the final output image will be adversely affected. This is because the subtracter 46 subtracts a constant value of the back color signal component (output from the Korg 47) from the background image signal, whereas the adder 4
The back screen portion of the foreground image signal added in step 4 has a difference between it and the back color signal component of the constant value due to color unevenness and uneven brightness, and this difference is directly added to the final addition composite output image. Because it appears.

The present invention has been made in view of these points, and it is an object of the present invention to provide a ROMA key device that can prevent the influence of unevenness in color, level, etc. of the back screen of a foreground image from appearing on an output image that has been additively synthesized. purpose.

[Means to solve the problem]

The chromakey device according to the present invention includes a key signal generating means for extracting a key signal from a foreground image signal, a subtracting means for subtracting the foreground image signal from a background image signal, and an output signal from the subtracting means. The above problem is solved by comprising a multiplication means for multiplying an inverted signal of a key signal from the multiplication means, and an addition means for adding the output signal from the multiplication means and the foreground image signal.

Here, a signal obtained by multiplying the foreground image signal by an inverted signal of the key signal may be sent to the subtraction means, and the signal may be subtracted from the background image signal.

[For production]

Since the foreground image signal itself is subtracted from the background image signal before addition and synthesis, even if there is color unevenness in the bank screen part, it will be canceled out during addition and synthesis with the foreground image signal, and there will be no difference in the addition and synthesis output signal. , there is no adverse effect caused by color unevenness in the back screen portion of the foreground image.

〔Example〕

FIG. 1 shows a block circuit diagram showing one embodiment of a chromakey device according to the present invention.

In this FIG. 1, three input terminals 11v111+,
At 11°, for example, a foreground image FG as shown in FIG.
A luminance signal (Y signal) and two color signals (1 and Q signals) are respectively supplied to the key signal generation and hue suppression circuit 1.
It has been sent to 2.

That is, a signal on any horizontal line L of the foreground image FC appears as Fl in FIG. 3, and is supplied to the key signal generation and hue suppression circuit 12. However, in FIG. 3, in order to simplify the illustration, it is shown in the form of, for example, an NTSC composite color video signal, but in reality, this luminance signal (Y signal) and two color signals ( I, Q signals) are supplied. Here, the foreground image FC is
It has a configuration in which a subject OB such as a person is placed in front of a back screen BS of a predetermined back color (blue in terms of numbers), and on the signal Fl there is a display according to the brightness and hue of the back screen BS. A back color display signal portion a and a portion displaying the object OB appear.

The key signal generation and hue suppression circuit 12 performs hue suppression processing such as suppressing the hue of the back screen BS portion to turn it gray, and outputs the output signals (Y signal and ■, Q signals) to the KOG ( For example, it is sent to an NTSC coder) 13. F2 in FIG. 3 shows a specific example of the signal after this hue suppression processing as the output from the Korg 13,
The portion of the foreground image FC corresponding to the back screen BS is a portion C that is displayed in gray on the signal F2. Further, the key signal generation and hue suppression circuit 12 generates a key signal such as that shown at K in FIG. 3, for example, based on the input foreground image signal.

This key signal has "0" in the back screen BS part of the foreground image FG and "l" in the object OB part.

The signal F2 after the hue suppression process is sent to an adder 14 and added to the background image signal that has been subjected to a predetermined process.

A background image signal, for example an NTSC composite color video signal for displaying a background image BG as shown in FIG. 2B, is supplied to the input terminal 21 and sent to the subtracter 22. A signal on an arbitrary line L of this background image BG appears, for example, as shown in 81 in FIG. Here, the signal F2 is supplied to the subtracter 22 via the multiplier 15 and the adder 16, and this signal is subtracted from the background image signal.

Here, the above key signal includes an inverter (inverting circuit) 1
7 to a multiplier 15 and is multiplied by the signal F2 to obtain the foreground image FC of the signal F2.
Only the portion C corresponding to the back screen BS of is extracted. Further, the key signal is sent to a multiplier 18 and multiplied by a variable level input signal. This input signal is adjusted to a level approximately equal to the level of the portion C, and is multiplied to extract only the portion of the object OB of the foreground image FC. The output signal from the multiplier 1 is sent to the adder 16 and added to the output signal from the multiplier 15, resulting in a signal as shown at F3 in FIG. sent to. The signal F3 in FIG. 3 includes a portion C (output signal from the multiplier 15) corresponding to the hack screen BS of the foreground image FC, and a portion d (output signal from the multiplier 18) corresponding to the object 0. )
It consists of.

In the subtracter 22, the signal F3 is subtracted from the background image signal B1, resulting in a signal B2 in FIG.

The broken line of this signal B2 indicates the signal B1, and by subtracting the signal F3 from this signal B1, a signal like the solid line is obtained.

The output signal from the subtracter 22 is sent to a multiplier 23,
It is multiplied by the inverted key signal from the inverter 17.

Therefore, with respect to signal B2, only the portion of the object OB in the image is set to "0", and signal B3 in FIG. 3 is obtained. This signal B3 corresponds to the object part OB by lowering the signal level of the area corresponding to the back screen BS in the background image by the level of each position of the back screen BS corresponding to each position in the area. The signal has all the levels in the region set to "0". This signal B3 is sent to adder 14.

In the X adder 14, the signal F2 and the signal B3 are added, and a signal as shown in B4 in FIG. 3 is obtained. This third
The broken line in B4 in the figure shows the signal B3, and the gray level part C in the signal F2 is in the section corresponding to the hack screen BS in the above image, and the gray level part C in the signal F2 is in the section corresponding to the object OB. By adding the object signal portions of , an image is created in which the object OB is inserted into the background image at the original signal level, or the back color portion BS of the foreground image FC is replaced by the background image BG. A signal for displaying an image is obtained from output terminal 24.

With this configuration, even if the back screen BS of the foreground image FC has uneven brightness and hue due to non-uniform illumination or dirt, this back screen B
Since the image signal representing S itself is subtracted from the background image signal by the subtracter 22, when the adder 14 adds and synthesizes the foreground image signal and the background image signal, the hack screen BS
The image signal components in the portion are exactly canceled out, and it is possible to prevent the occurrence of adverse effects due to uneven brightness and hue. Furthermore, the foreground image signal is multiplied by the inverted signal of the key signal by the multiplier 15, and the adder 16 adds a signal at a level corresponding to a predetermined hack color to the subject-corresponding area of this signal. The background image signal from is a signal obtained by subtracting the hack color equivalent level over the entire screen. Thereby, when the multiplier 23 multiplies the inverted key signal and the adder 14 adds the signal to the foreground image signal, the connection or continuity between the subject part and the background part can be further enhanced.

Note that the present invention is not limited to the above embodiment, and for example, the multiplier 18 and the adder 16 can be omitted. Furthermore, the multiplier 15 may be omitted.

〔Effect of the invention〕

According to the chroma key device of the present invention, a signal obtained by subtracting a foreground image signal from a background image signal is multiplied by an inverted signal of a key signal extracted from the foreground image signal, and this multiplied signal and the foreground image signal are added. Therefore, during this addition,
Changes in brightness and hue due to dirt on the hack screen of the foreground image are canceled out, and an adverse effect on the output image can be prevented.

Furthermore, a signal obtained by multiplying the foreground image signal by the inverted signal of the key signal is subtracted from the background image signal, and a signal obtained by multiplying this subtracted signal by the inverted signal of the key signal is added to the foreground image signal. The object part and the back screen part are clearly distinguished, and a good ROMA key image can be obtained.

FIG. 2 is a block circuit diagram showing an example of a chromakey device.

lv, 11+, 11o...Foreground image signal input terminal 2
...Key signal generation and hue suppression circuit 3...
...Korg (NTSC coder) 41.16...
Adder 5, 18, 23... Multiplier 7... Inverter... Background image signal input terminal 2... Subtractor 4... Output terminal

[Brief explanation of drawings]

Claims (2)

[Claims] (1) Key signal generation means for extracting a key signal from a foreground image signal; subtraction means for subtracting the foreground image signal from a background image signal; 1. A chromakey device comprising: a multiplier for multiplying an inverted signal; and an adder for adding an output signal from the multiplier and the foreground image signal. (2) The chromakey device according to claim 1, wherein a signal obtained by multiplying the foreground image signal by an inverted signal of the key signal is sent to the subtracting means, and the signal is subtracted from the background image signal.