Image analysis – Image segmentation
Reexamination Certificate
1997-11-17
2002-09-17
Boudreau, Leo (Department: 2621)
Image analysis
Image segmentation
C382S199000
Reexamination Certificate
active
06453069
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image segmentation method for segmenting the image region to be extracted from an input image using a reference image, an image identification method for identifying the image region to be extracted from an input image using a reference image, an image segmentation apparatus, an image processing apparatus and method for extracting a specific image region from an image, and a storage medium storing the image processing method.
As general techniques for implementing image extraction, a chromakey method using a specific color background, a videomatte method for generating a key signal by predetermined image processing (histogram processing, difference processing, differential processing, contour enhancement, contour tracing, and the like) (
The Television Society Technical Report, Vol.
12, pp. 29-34, 1988), and the like are known.
A technique for performing image extraction based on the difference from the background image is a state-of-the-art one, and for example, Japanese Patent Laid-Open No. 4-216181 discloses a technique for detecting or extracting a target object in a plurality of specific regions in an image by setting a mask image (specific processing region) in difference data between the background image and the image to be processed. Furthermore, Japanese Patent Publication No. 7-16250 discloses a technique that uses a color model of the object to be extracted to implement image extraction by obtaining the existence probability distribution of the object to be extracted from color-converted data of an original image including background and lightness difference data between the background image and the original image.
In the difference method from the background image, the luminance level or color component difference between the pixels of the background image and the subject image is normally expressed by a predetermined evaluation function, and the evaluation function is subjected to thresholding to extract a region having a difference level equal to or higher than a predetermined value. As the evaluation function, the correlation between blocks having individual points as centers and a predetermined size (Rosenfeld, A. and Kak, A. C., Digital Picture Processing (2nd ed.), Academic Press, 1982), a normalized principal component features (
Journal of the Institute of Electronics, Information and Communication Engineers
, Vol.
J74-D-II, pp. 1731-1740), a weighted sum value of a standard deviation and a difference value (
Journal of the Television Society
, Vol. 45, pp. 1270-1276, 1991), a local histogram distance associated with hue and luminance level (
Journal of the Television Society
, Vol. 49, pp. 673-680, 1995), and the like are used.
As a technique for identifying or recognizing a specific object, the following method is popularly used. That is, a model image or template associated with that object is prepared in advance. An image region of the object to be identified is separated from other regions, the size of the image region to be identified is normalized or its position is fixed, or a plurality of model images having different sizes are prepared. Scanning a target image, the similarities between the model image or template and the object to be identified are determined using a measure such as correlation or the like.
The background difference method poses a problem when a partial region which has a similar luminance, color, or pattern to the background image is included in the object to be extracted. In this case, since no difference in that region is estimated between the background image and the input image including the object to be extracted, extraction or detection errors take place. As a step against such problem, Japanese Patent Laid-Open No. 8-44844 adopts a method of calculating the gradients of both the background image and the input image, and taking logical OR of the difference absolute value between the gradients and that of image signals. On the other hand, Japanese Patent Laid-Open No. 8-212350 adopts a method of performing thresholding by calculating a feature, the rate of its change with respect to changes in pixel density of the input image of which decreases when the background image has a middle pixel density, and increases when the background image has a high or low pixel density.
However, in image extraction, the chromakey method is hard to use outdoors due to serious background limitations such as a requirement for a specific color background, and causes color omissions in the subject region having the same color as the background. On the other hand, in the videomatte method, since contour designation must be manually and accurately performed in units of pixels, such operation requires much labor and skill.
Furthermore, in the background difference method, the background is hard to distinguish from the subject in a partial region of the subject similar to the background, and this method does not normally allow image sensing condition differences (e.g., the exposure condition, magnification, illumination condition, focusing condition, view point position, and the like) between the background image and input image. Especially, when background obtained by removing the subject from the input image is different from the background image, the tolerance to their difference is considerably low even if they are similar to each other. In addition, it is very hard to extract contour and three-dimensional shape details of the subject while removing the noise influence.
Also, the background difference method requires distinct image characteristic differences (e.g., pixel values and the like) between the background image and the subject region everywhere, and it is hard to apply the method to a general background. Even in the methods that take a step against the partial region of the subject similar to the background (Japanese Laid-Open Patent Nos. 8-44844 and 8-212350), for example, when the rate of spatial change in pixel value is small, the subject is hardly or insufficiently distinguished from the background. Hence, it is difficult to stably maintain high extraction precision by automatic processing in a practical use.
When the shadow of the object to be extracted is present in the image in the vicinity of the object, it is hard for either method to extract the image region to be extracted alone and to automatically remove the shadow.
Furthermore, in the method of identifying or recognizing a specific target image, the segmentation processing from other regions in the above-mentioned pre-processing normally constitutes in separable parts and is complicated and hard to attain. On the recognition technique, also, it is difficult to automatically normalize the size, position, and the like since the size and position of the object to be recognized are not detected in advance. Furthermore, the number of model images having different sizes that can be prepared is limited due to storage capacity limitations on the database, resulting in poor versatility.
SUMMARY OF THE INVENTION
It is, therefore, the first object of the present invention to provide an image segmentation method, which can precisely and automatically detect the existence range of an intruder in the input image, and can precisely detect the existence range of the object to be extracted or recognized.
It is the second object of the present invention to provide an image segmentation method which can stably extract an image from the input image even when the reference image and the input image have differences resulting from variations of the image sensing condition, illumination condition, and the like therebetween.
It is the third object of the present invention to provide an image identification method and apparatus, which can stably and automatically recognize the object to be recognized without being influenced by any differences of the image size and position of a subject, and are excellent in terms of economy.
It is the fourth object of the present invention to provide an image segmentation method which can perform hig
Hatanaka Koji
Katayama Tatsushi
Matsugu Masakazu
Canon Kabushiki Kaisha
Morgan & Finnegan , LLP
Sherali Ishrat
LandOfFree
Method of extracting image from input image using reference... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of extracting image from input image using reference..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of extracting image from input image using reference... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2829159