Guided Color Transient Improvement Filtering in Video Coding

A method for guided filtering by an encoder, the method comprising:

• receiving a target image to be encoded by an encoder and a guide image, wherein both the target image and the guide image represent similar scenes and each comprises a first color component and a second color component;
• encoding the target image with the encoder to generate a coded image;
• decoding the coded image with a decoder to generate a decoded image, the decoded image comprising a decoded first color component and a decoded second color component;
• selecting a color transient improvement (CTI) filter to filter pixels of the decoded image to generate an output color component image;
• computing filtering coefficients for the color transient improvement (CTI) filter, wherein the filtering coefficient computation is based on minimizing an error measurement between pixel values of the output color component image and corresponding pixel values of the second color component in the guide image, wherein the CTI filter comprises a first set of filtering coefficients and a second set of filtering coefficients, wherein generating the output color component image comprises combining the result of filtering the first color component of the decoded image with the first set of filtering coefficients with the result of filtering the second color component of the decoded image with the second set of filtering coefficients;
• and
• transmitting the CTI filtering coefficients to a decoder.