Matting method for extracting foreground object and apparatus for performing the matting method
A matting method and apparatus for extracting a foreground object are disclosed. The matting method includes extracting one or more pixels from an input image and a trimap; calculating a first processing cost by extracting one or more nonlocal neighboring pixels; calculating a second processing cost by extracting one or more local neighboring pixels; and performing matting on the input image by estimating an opacity value for each of the extracted pixels based on the first and second processing costs. Accordingly, it is possible to perform high-quality image matting, and thus increase a performance in extracting a to foreground object from the input image, so that the matting method and apparatus can be applied to multiple-purpose image editing software.
1. A matting method for extracting a foreground object, which is performed by an information processing apparatus capable of digital signal processing, the matting method comprising:
extracting one or more pixels from a received input image and a received trimap of the input image;
calculating a first processing cost based on a first predefined cost function by extracting one or more nonlocal neighboring pixels for each of the extracted pixels which establish nonlocal relationships with each of the extracted pixels;
calculating a second processing cost based on a second predefined cost function by extracting, for each of the extracted pixels, one or more local neighboring pixels which are included within a predefined range for extraction and establish local relationships with each of the extracted pixels; and
performing matting on the input image by estimating an opacity value of each of the extracted pixels based on both the first processing cost and the second processing cost,
wherein the trimap is an image that represents the input image by dividing the input image into a foreground region, a background region, and an unknown region, and the extracting of the one or more pixels comprises extracting one or more pixels with an indefinite opacity value that are located in the input image and the unknown region of the trimap.
2. The matting method of claim 1 , wherein the calculating of the first processing cost comprises generating a feature vector for each of the extracted pixels using color information and location information of each of the extracted pixels; extracting the one or more nonlocal neighboring pixels for each of the extracted pixels, which establish nonlocal relationships with each of the extracted pixels, by calculating distances among the pixels based on the generated feature vectors; and calculating the first processing cost for each of the extracted pixels using the extracted nonlocal neighboring pixels.
3. The matting method of claim 2 , wherein the extracting of the one or more nonlocal neighboring pixels comprises calculating Euclidean distances among the extracted pixels using a K-nearest neighbors algorithm based on the feature vectors and extracting one or more pixels with smallest distances as the one or more nonfocal neighboring pixels.
4. The matting method of claim 1 , wherein the calculating of the second processing cost comprises extracting one or more pixels within the predefined range for extraction that is based on each of the extracted pixels as the one or more local neighboring pixels that establish local relationships with each of the extracted pixels, and calculating the second processing cost for each of the extracted pixels using the one or more local neighboring pixels.
5. The matting method of claim 1 , wherein the performing of the matting on the input image comprises computing a final processing cost using both the first processing cost and the second processing cost such that a processing cost for each of the extracted pixels can be minimized, and estimating an optimized opacity value for each of the extracted pixels based on the final processing cost.
6. The matting method of claim 5 , wherein the optimized opacity value for each of the extracted pixels is used for the performing of the matting on the input image, thereby making it possible to extract a foreground object from the input image.