Coding and decoding method for images or videos

Abstract

A coding and decoding method for images or videos is provided by embodiments of the present invention to improve coding and decoding efficiency. The method includes: establishing a visual dictionary, wherein, the visual dictionary includes one or more visual words; extracting features from a specific object in an image; determining whether there is a visual word in the visual dictionary matching the specific object by using a feature matching method; obtaining the index of the visual word matched and a geometric relationship between the specific object and the visual word matched, wherein, the geometric relationship is represented by a project parameter; entropy coding the index of the visual word matched and the project parameter instead of entropy coding the specific object.

The invention claimed is: 
     
       1. A coding method for images or videos, comprising:
 establishing a visual dictionary, wherein, the visual dictionary comprises one or more visual words; 
 extracting features from a specific object in an image; 
 determining whether there is a visual word in the visual dictionary matching the specific object by using a feature matching method; 
 obtaining the index of the visual word matched and a geometric relationship between the specific object and the visual word matched; 
 wherein, the geometric relationship is represented by a project parameter; 
 entropy coding the index of the visual word matched and the project parameter instead of entropy coding the specific object. 
 
     
     
       2. The method of  claim 1 , further comprising:
 calculating differences between the image and the visual word matched; 
 coding the differences by using a sparse coding method or a traditional coding method to obtain residuals; 
 entropy coding the residuals with the index of the visual word matched and the project parameter. 
 
     
     
       3. The method of  claim 1 , wherein, each visual word comprises a visual object or a texture object, and corresponding features thereof. 
     
     
       4. The method of  claim 1 , wherein, the project parameter comprises magnification, deflation, rotation, affine, relative position. 
     
     
       5. The method of  claim 1 , wherein, determining whether there is a visual word in the visual dictionary matching the specific object comprises:
 comparing extracted local features of the specific object with local features of a visual word in the visual dictionary to obtain a local feature pair which comprises two identical or similar local features respectively extracted from the specific object and obtained from the visual word; 
 calculating geometric distributions of the local features corresponding to the local feature pair, respectively in the specific object and in the visual word; 
 determining whether the geometric distributions of the local features corresponding to the local feature pair, respectively in the specific object and the visual word, are consistent; considering the visual word as matching the specific object if the two geometric distributions are consistent. 
 
     
     
       6. The method of  claim 5 , wherein, before comparing extracted local features of the specific object with local features of a visual word in a visual dictionary, the method further comprises:
 combining the local features of each specific object to obtain a global feature; 
 searching the visual dictionary for a candidate visual word with the most similar global feature with that of the specific object. 
 
     
     
       7. The method of  claim 6 , wherein, SIFT algorithm is used to extract the local features of the specific object. 
     
     
       8. A decoding method for images or videos, comprising:
 entropy decoding a code stream of an image to obtain an index and a project parameter of a visual word; 
 obtaining an image of a visual object from a visual dictionary according to the index of the visual word; 
 adjusting the image of the visual object with reference to the project parameter; 
 overlapping adjusted images of all of visual objects to obtain a decoded image. 
 
     
     
       9. The method of  claim 8 , further comprising:
 entropy decoding the code stream to obtain residuals; 
 reversely decoding the residuals to obtain differences between the image to be decoded and the visual word; 
 overlapping the adjusted image of all of the visual objects and the differences to obtain a decoded image.