Coding and decoding method for images or videos

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.