A method of deriving intra prediction data based on a planar prediction mode includes the following operations: obtaining multiple first reconstructed row samples and a second reconstructed row sample in an adjacent above row to a current block, the first reconstructed row samples extending from first to last columns of the current block, the second reconstructed row sample corresponding to an adjacent right column to the current block; obtaining multiple first reconstructed column samples and a second reconstructed column sample in an adjacent left column to the current block, the first reconstructed column samples extending from first to last rows of the current block, the second reconstructed column sample corresponding to an adjacent below row to the current block; and deriving the intra prediction data corresponding to the current block based on a width and a height of the current block and the obtained reconstructed row and column samples.