Specified image-area extracting method and device

• US 6,088,137 A
• Filed: 07/25/1996
• Issued: 07/11/2000
• Est. Priority Date: 07/28/1995
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Tomizawa, Naoki
• Primary Examiner(s): Coles, Edward L.
• Assistant Examiner(s): HASKINS, TWYLER LAMB
• Application Number:
  US08/690,319
• Time in Patent Office: 1,447 Days
• Field of Search: 358/520, 358/522, 358/523, 358/528, 358/538, 382/118, 382/190, 382/165, 348/652, 348/592, 348/577, 348/169, 348/29, 348/30
• US Class Current: 358/538
• CPC Class Codes: G06V 40/162 using pixel segmentation or colour matching
• CPC Class Codes: H04N 19/17 the unit being an image region, e.g. an object
• CPC Class Codes: H04N 19/20 using video object coding
• CPC Class Codes: H04N 19/30 using hierarchical techniques, e.g. scalability H04N19/63 takes precedence
• CPC Class Codes: H04N 7/14 Systems for two-way working H04N7/12, H04N7/173 take precedence
• 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

Abstract

A face (skin color) area of a person is extracted with minimized error irrespective of different skin colors of the human races. A hue value calculating portion determines a hue value from an input image (RGB signal). A primary discriminating portion extracts pixels having hue value that lies in a specified range defined by limiting values outputted from a control portion. A pixel-counting portion counts the extracted pixels. The control portion selects a threshold value for extracting a face area according to the count of the extracted pixels and outputs the threshold value to a face-area extracting portion which in turn extracts a face area according to the threshold value.

Claims

1. A specified image-area extracting method comprising the steps of:

a) deriving a value of a color component having low correlation with luminance from each pixel of an input colored image;

b) determining distributions of all pixels of the input colored image according to every color component value;

c) determining a specified area of each color component value in the input colored image based on the determined distributions; and

d) extracting a pixel whose color component value belongs to the specified area.

2. The specified image-area extracting method as defined in claim 1, wherein hue is used as the color component.

3. The specified image-area extracting method as defined in claim 1, wherein said step b) comprises:

b1) preparing a histogram of the color component values; and

b2) determining existence of a peak having a frequency exceeding a preset value in a preset range of values of the color component,

two specified preset areas being selected for determining in said step c) based on the determination in said step b2).

4. The specified image-area extracting method as defined in claim 3, wherein the preset range of the color component values is limited by a fixed upper limit value and a fixed lower limit value.

17. The specified image-area extracting area extracting method of claim 1, further including the step (e) forming a color video image for video communication.

19. The specified extracting device according to claim 1, further including means for video communicating a color video image.

5. A specified area extracting device comprising:

arithmetic processing means for determining a color component value having low correlation with luminance for each pixel in an input colored image;

a frame memory for storing the input colored image and the color component value determined by said arithmetic processing means;

discriminating means for discriminating whether the determined color component value is included within a preset specified range of color components values;

counting means for counting the number of pixels in the input colored image having a color component value within the preset specified range according to the discrimination by said discriminating means;

specified image-area extracting, means for extracting an image within the preset specified range of color component values from said frame memory; and

control means for controlling said arithmetic processing means, said discriminating means, said counting means and said specified image-area extracting means, said control means comparing a count value of said counting means with a preset value and selecting two specified ranges of the color component values as the preset specified range extracted by said specified image-area extracting means based on the comparison.

6. The specified area extracting device as defined in claim 5, wherein an upper limit value and a lower limit value limit the preset specified range of color component values, the upper limit value and the lower limit value being constant values.

7. A specified area extracting device comprising:

a frame memory for storing an input colored image;

pixel extracting means for deriving a color component value having low correlation with luminance for each pixel of the input colored image stored in said frame memory, determining distributions of all pixels of the input colored image according to the color component values, determining a specified area of the color component values in the input colored image based on the distributions, and extracting pixels of the input colored image belonging to the determined specified area;

first means for preparing a histogram of the extracted pixels in an input color space;

second means for determining a specified area in the input color space from distributions of the prepared histogram;

third means for applying the determined specified area to an input image of a proceeding frame and extracting pixels belonging to the determined specified area from the input colored image; and

control means for controlling said pixel extracting means and said first, second and third means.

8. The specified area extracting device as defined in claim 7, wherein said control means periodically controls determination of the specified area in a color space and extraction of pixels belonging to the determined specified area by repeatedly applying the determined specified area to inputted images until a new specified area is determined.

9. The specified area extracting device as defined in claim 7, further comprising input processing means for processing an image sequence to be used as the input colored image.

10. The specified area extracting device as defined in claim 8, further comprising input processing means for processing an image sequence to be used as the input colored image.

11. An apparatus for extracting, a specific area from an image comprising:

color component determination means for determining hue values for each pixel of the image;

discriminating means, coupled to said color component determination means, for designating a specific range of the hue values and extracting pixels from the image having hue values determined as within the specific range;

counting means, coupled to said discriminating means, for counting a number of pixels extracted by said discriminating means;

control means, coupled to said counting means, for determining a range of hue values for area extraction based on the counted number of pixels; and

area extracting means, coupled to said control means, for extracting a specific area of the image having hue values within the determined range of hue values.

12. The apparatus for extracting a specific area from an image of claim 11, wherein said discriminating means designates the specific range in accordance with a predetermined fixed upper limit and a predetermined fixed lower limit of the hue values.

13. The apparatus for extracting a specific area from an image of claim 11, wherein said control means determines the range of hue values as one of a first range and a second range in accordance with the counted number of pixels.

14. An apparatus for extracting a specific area from an image comprising:

color component determination means for determining hue values for each pixel of the image;

histogram means, coupled to said color component determination means, for preparing a histogram of the hue values;

noise removing means, coupled to said histogram means, for smoothing the histogram by eliminating portions of the histogram having a frequency less than a predetermined value;

discriminating means, coupled to said noise removing means, for designating a specific range of the hue values in the smoothed histogram and detecting whether a histogram peak is within the specific range;

control means, coupled to said discriminating means, for designating a color extraction mode and a threshold for area extraction based on histogram peak detection by said discriminating means; and

area extracting means, coupled to said control means, for extracting a specific area of the image in accordance with the designated color extraction mode and the designated threshold.

15. The apparatus for extracting a specific area from an image of claim 14, wherein said discriminating means designates the specific range in accordance with a predetermined fixed upper limit and a predetermined fixed lower limit of the hue values.

16. A specified image-area extracting method comprising the steps of:

a) deriving a value of a color component having low correlation with luminance from each pixel of an input colored image, the input colored image being a colored image of its skin of a living being;

b) determining distributions of all pixels of the input colored image according to every color component value;

c) determining a specified area of each color component value in the input colored image based on the determined distributions; and

d) extracting a pixel whose color component value belongs to the specified area.

18. A specified area extracting device comprising:

arithmetic processing means for determining a color component value having low correlation with luminance for each pixel in an input colored image, wherein the colored image being a colored image of the skin of a living being;

a frame memory for storing the input colored image and the color component value determined by said arithmetic processing means;

discriminating means for discriminating whether the determined color component value is included within a preset specified range of color component values;

counting means for counting the number of pixels in the input colored image having a color component value within the present specified range according to the discrimination by said discriminating means;

specified image-area extracting means for extracting an image within the preset specified range of color component values from said frame memory; and

control means for controlling said arithmetic processing means, said discriminating means, said counting means and said specified image-area extracting means, said control means comparing a count value of said counting means with a preset value and selecting two specified ranges of the color component values as the present specified range extracted by said specified image-area extracting means based on the comparison.