Key signal generating apparatus and picture synthesis apparatus,

Television – Image signal processing circuitry specific to television – Special effects

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Details

348591, 348595, H04N 974, H04N 975

Patent

active

061280461

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a key signal generating apparatus and a picture synthesis apparatus, and a key signal generating method and a picture synthesis method. More particularly, this invention relates to a key signal generating apparatus and a picture synthesis apparatus, and a key signal generating method and a picture synthesis method which are adapted for detecting change of pixel value between pixels constituting pictures to generate a key signal on the basis of the change of the pixel value, thereby making it possible to obtain an accurate key signal.


BACKGROUND ART

For example, in movies and other image productions, in the case where various simulations of pictures (images) are carried out, or any special effect is given to pictures, a remarked portion (object) is extracted from picture, or the extracted portion is synthesized with respect other pictures. Such a partial extraction from picture and/or synthesis (of the extracted portion) is carried out by using key signal.
As a technology relating to such a key signal, an example thereof is proposed in the specification and the drawings of the U.S. Pat. No. 4,488,169 (Registered Date: Dec. 11, 1984) by the applicant of this invention.
As the key signal, there are a key signal called hard key and a key signal called soft key. Now, in the case where, e.g., the remarked portion within picture used for generating the key signal is caused to be the foreground (foreground picture), and the portion except for the above is caused to be the background (background picture), a binary key signal (mask picture) in which the range of the foreground in the picture is caused (assumed) to be 1 and the range of the background is caused (assumed) to be 0 as shown in FIG. 1A is called hard key. On the contrary, a key signal which can take not only two values of 0 and 1, but also continuous real numbers within the range from 0 to 1 as shown in FIG. 1B in consideration of alias and/or motion blur which will be described later taking place in picture is called soft key. Here, the area where the key signal takes values within the range from 0 to 1 is called gray area as the occasion may demand.
Namely, it can be said that the hard key is a signal having a sharp boundary (border) line (signal in which inclination (gradient) of the boundary line where the key signal changes from 0 (or 1) to 1 (or 0) is sharp), and the soft key is a signal having a smooth (gentle) boundary (border) line (signal in which inclination (gradient) of the boundary line where the key signal changes from 0 (or 1) to 1 (or 0) is smooth (gentle)).
It is now assumed that a (a value) shown in FIGS. 1A and 1B indicates continuous key signal values and also indicates, in this case, values of the key signal of pixel units at the same time. In practice, e.g., continuous key signals are caused to undergo filtering by the range of pixel, etc. to use, as the key signal of the pixel unit, the result by that filtering at the center of corresponding pixel. In this case, in the picture, pixel value of the pixels at the boundary portion between the foreground and the background is a value in which respective signal components of the foreground and the background are interposed. From facts as above, it can be said that a indicates contribution ratio (factor) indicating to what degree the foreground contributes with respect to respective pixels.
Meanwhile, it is rare that in the case where both the foreground and the background are stationary, the boundary between the foreground and the background is positioned at the boundary line between pixels constituting a corresponding picture. Ordinarily, as shown in FIG. 2A, the boundary between the foreground and the background exists within the pixel having finite dimensions. However, since the pixel is the minimum unit constituting the picture, even if the boundary between the foreground and the background as described above exists within the pixel, that pixel is caused to have color or brightness (pixel value) of any one of the foreground and the backg

REFERENCES:
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patent: 5495297 (1996-02-01), Fujimori
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