Cross-component planar prediction in image and video compression

A method of video encoding, comprising:

• predicting one or more first chroma samples in a chroma block to be encoded in a current picture based on one or more luma samples in a luma block in the current picture, the chroma block being predicted based at least on the luma block in the current picture, the luma block being reconstructed and collocated with the chroma block;
• predicting a second chroma sample in the chroma block based on the predicted one or more first chroma samples and at least one reference chroma sample of the chroma block, the second chroma sample being different from the one or more first chroma samples, the at least one reference chroma sample being adjacent to the chroma block;
• encoding prediction information in a bitstream indicating that the chroma block is predicted based at least on the luma block in the current picture;
• and
• encoding the chroma block in the bitstream based on the predicted second chroma sample.

A non-transitory computer-readable storage medium storing instructions which when executed by a processor cause the processor to perform an encoding method comprising:

• predicting one or more first chroma samples in a chroma block to be encoded in a current picture based on one or more luma samples in a luma block in the current picture, the chroma block being predicted based at least on the luma block in the current picture, the luma block being reconstructed and collocated with the chroma block;
• predicting a second chroma sample in the chroma block based on the predicted one or more first chroma samples and at least one reference chroma sample of the chroma block, the second chroma sample being different from the one or more first chroma samples, the at least one reference chroma sample being adjacent to the chroma block;
• encoding prediction information in a bitstream indicating that the chroma block is predicted based at least on the luma block in the current picture;
• encoding the chroma block in the bitstream based on the predicted second chroma sample;
• and
• transmitting the bitstream.