Image encoding and decoding methods and devices thereof

An image decoding method applied to a decoding end, comprising:

• receiving a second image bit stream and a second difference image bit stream;
• decoding the second image bit stream and the second difference image bit stream to obtain a second image and a second difference image;
• performing upsampling on the second image based on a pre-set sampling ratio and a pre-set sampling method to obtain a third image;
• regulating pixel values of the second difference image based on a pre-set offset value to obtain a first difference image;
• and
• calculating a sum of the first difference image and the third image to obtain a first image.

An image encoding device comprising:

• a downsampling module, a first encoding module, a processing module, a first calculation module, a first regulation module and a second encoding module,
• wherein the downsampling module is configured to perform downsampling on a first image based on a pre-set sampling ratio and a pre-set sampling method to obtain a second image, and the first image is a high-resolution image or a high-resolution video frame, or the first image is a low-resolution image or a low-resolution video frame obtained by performing downsampling on the high-resolution image or the high-resolution video frame for at least one time;
• the first encoding module is configured to encode the second image to obtain a second image bit stream, and send the second image bit stream to a decoding end;
• the processing module is configured to process the second image based on a pre-set processing rule to obtain a third image having a resolution the same as that of the first image;
• the first calculation module is configured to calculate a difference between the third image and the first image to obtain a first difference image;
• the first regulation module is configured to regulate, based on a pre-set offset value, pixel values of the first difference image to fall within a pre-set range, to obtain a second difference image;
• and
• the second encoding module is configured to encode the second difference image in a pre-set encoding manner to obtain a second difference image bit stream, and send the second difference image bit stream to the decoding end to enable the decoding end to reconstruct the first image based on the second image bit stream and the second difference image bit stream.

An image decoding device comprising:

• a receiving module, a decoding module, an upsampling module, a second regulation module and a second calculation module;
• wherein the receiving module is configured to receive a second image bit stream and a second difference image bit stream;
• the decoding module is configured to decode the second image bit stream and the second difference image bit stream to obtain a second image and a second difference image;
• the upsampling module is configured to perform upsampling on the second image based on a pre-set sampling ratio and a pre-set sampling method to obtain a third image;
• the second regulation module is configured to regulate pixel values of the second difference image based on a pre-set offset value to obtain a first difference image;
• and
• the second calculation module is configured to calculate a sum of the first difference image and the third image to obtain a first image.