Video signal processor for detecting flesh tones in am image

• US 5,488,429 A
• Filed: 12/31/1992
• Issued: 01/30/1996
• Est. Priority Date: 01/13/1992
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Yamada, Takeshi, Sugiura, Hiroaki, Kuno, Tetsuya, Kojima, Kazuaki
• Primary Examiner(s): Kostak, Victor R.
• Assistant Examiner(s): Miller, John W.
• Application Number:
  US07/999,741
• Time in Patent Office: 1,125 Days
• Field of Search: 348/652, 348/653, 348/649, 348/650, 348/645
• US Class Current: 348/653
• CPC Class Codes: H04N 23/61 based on recognised objects
• CPC Class Codes: H04N 23/635 Region indicators; Field of view indicators
• CPC Class Codes: H04N 23/661 Transmitting camera control signals through networks, e.g. control via the Internet
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method
• CPC Class Codes: H04N 23/675 comprising setting of focusing regions
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation
• CPC Class Codes: H04N 5/208 for compensating for attenuation of high frequency components, e.g. crispening, aperture distortion correction
• CPC Class Codes: H04N 5/2621 Cameras specially adapted for the electronic generation of special effects during image pickup, e.g. digital cameras, camcorders, video cameras having integrated special effects capability
• CPC Class Codes: H04N 9/643 Hue control means, e.g. flesh tone control
• CPC Class Codes: H04N 9/646 for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters
• CPC Class Codes: H04N 9/75 Chroma key

Abstract

A flesh-tone area is detected based on color-difference and luminance signals constituting video signals, and luminance correction, color correction, and aperture correction are performed only on the flesh-tone area or a human face area identified in the flesh-tone area. The setting of a focus area or the setting of a photometric area for iris control, automatic gain control, automatic shutter control, etc., in a video camera, is performed with respect to the flesh-tone area or the human face area. Furthermore, based on the color-difference and luminance signals constituting the video signals, a background area is detected, and the video signals are divided into components representing a background area and components representing an object area. An image signal of a desired hue or a still image is superimposed on the detected background area, or special processing is performed on the video signals representing the object area other than the detected background area.

Claims

1. A video signal processor receiving a luminance signal and color-difference signals as video signals, comprising:

first means for outputting a value based upon the received color-difference signals by referencing a predetermined table;

second means for comparing the output value with the luminance signal and outputting a result of the comparison as a flesh-tone detection signal; and

third means for controlling gains of the plurality of color-difference signals, independently, in accordance with the presence or absence of the flesh-tone detection signal.

2. A video signal processor receiving a luminance signal and color-difference signals as video signals, comprising:

first means for outputting a value based upon the received color-difference signals by referencing a predetermined table;

second means for comparing the output value with the luminance signal and outputting a result of the comparison;

third means for extracting only low-frequency components from the result of the comparison;

fourth means for slicing the extracted low-frequency components by a predetermined slice level and outputting a resultant signal as a flesh-tone detection signal; and

fifth means for controlling the gains of the plurality of color-difference signals, independently, in accordance with a value of the flesh-tone detection signal.

3. A video signal processor receiving a luminance signal and color-difference signals as video signals, comprising:

first arithmetic means for adding a first color-difference signal to, or subtracting the first color-difference signal from, a second color-difference signal;

first gain control means for controlling an amount of the first color-difference signal to be added to or subtracted from the second color-difference signal;

second arithmetic means for adding the second color-difference signal to, or subtracting the second color-difference signal from, the first color-difference signal;

second gain control means for controlling an amount of the second color-difference signal to be added to or subtracted from the first color-difference signal;

first means for outputting a signal based upon the first and second color-difference signals by referencing a predetermined table;

second means for comparing the output signal with the luminance signal and outputting a result of the comparison;

third means for extracting only low-frequency components from the result of the comparison;

fourth means for slicing the extracted low-frequency components by a predetermined slice level and outputting a resultant signal as a flesh-tone detection signal; and

fifth means for controlling said first and said second gain control means, independently, in accordance with a value of the flesh-tone detection signal.

4. A method of adjusting a color difference signal of an image in a video signal processor comprising the steps of:

(a) detecting flesh tone in areas of the image based upon a luminance signal and saturation level of the color difference signals of the image and generating a flesh tone detecting signal; and

(b) controlling gains of the color difference signals based upon the generated flesh tone detecting signal;

wherein the step (a) includes the substeps of;

(i) receiving, in a memory, the color difference signals of the image,

(ii) outputting a signal indicative of color signal saturation level from the memory, based upon the received color difference signals;

(iii) comparing the output signal from the memory and the luminance signal; and

(iv) outputting a signal indicative of flesh-tone or non-flesh-tone in an area of the image based upon the comparison of step (iii).

5. The method of claim 4 wherein a signal indicative of flesh tone is output in step (iv) if the output signal from the memory is within a predetermined range of the luminance signal.

6. The method of claim 5, wherein the predetermined range is a range encompassing fractional percentages of the luminance signal.

7. A method of adjusting a color difference signal of an image in a video signal processor comprising the steps of:

(a) detecting flesh tone in areas of the image based upon a luminance signal and saturation level of the color difference signals of the image and generating a flesh tone detecting signal; and

(b) controlling gains of the color difference signals based upon the generated flesh tone detecting signal;

wherein step (a) includes the substeps of;

(i) outputting a signal indicative of color signal saturation level based upon the color difference signals; and

(ii) comparing the output signal and the luminance signal to produce a signal indicative of flesh tone or non flesh tone in an area of the image.

8. The method of claim 7, further comprising the steps of:

(c) extracting only low frequency components from the signal produced in step (a)(ii); and

(d) slicing the extracted low frequency components by a predetermined slice level and outputting a resultant signal as the flesh tone detecting signal for use in controlling gains in step (b).

9. A method of adjusting a color difference signal of an image in a video signal processor comprising the steps of:

(a) detecting flesh tone in areas of the image based upon a luminance signal and saturation level of the color difference signals of the image and generating a flesh tone detecting signal; and

(b) controlling gains of the color difference signals based upon the generated flesh tone detecting signal; and

wherein step (a) includes the steps of;

(i) utilizing the color difference signals to access a table pre-stored in memory; and

(ii) comparing the accessed value to the luminance signal to generate a signal indicative of flesh tone or non-flesh tone in an area of the image.

10. The method of claim 9, wherein a signal indicative of flesh tone is output in step (iv) if the accessed value is within a predetermined range of the luminance signal.

11. A video signal processor, comprising:

a flesh tone detector receiving luminance and color difference signals and detecting flesh tone in an image represented by the luminance and color difference signals, the flesh tone detector utilizing the color difference signals to access a table prestored in memory, comparing the accessed value to the luminance signal and generating an output as a result of the comparison; and

a gain controller for controlling a gain of at least one of said luminance and color difference signals based on the output from said flesh tone detector.