Image encoding/decoding method and device, and recording medium in which bitstream is stored

A method of encoding an image, the method comprising:

• determining whether or not to perform a function-based intra-prediction for the current block;
• performing intra-prediction for the current block for generating a prediction block of the current block;
• generating a residual block by subtracting the prediction block from the current block;
• and
• encoding the current block by encoding the residual block into a bitstream,
• wherein, when the function-based intra-prediction is performed for the current block, the performing intra-prediction comprises
• deriving a parameter for generating a function;
• performing intra-prediction by using the function based on the derived parameter;
• and
• encoding a prediction mode index indicating that the function-based intra-prediction is performed for the current block,
• wherein the prediction mode index is flag information signaled through a bitstream, having a first value indicating that the function-based intra-prediction is performed or a second value indicating that the function-based intra-prediction is not performed, and
• wherein the parameter for generating the function is derived based on at least one among a maximum sample value and a minimum sample value of previously reconstructed reference samples neighboring the current block, the maximum sample value being a value of a sample having a maximum value among values of the previously reconstructed reference samples, and the minimum sample value being a value of a sample having a minimum value among the values of the previously reconstructed reference samples.

A computer-readable recording medium storing a bitstream which is generated by a method of encoding an image, the method comprising:

• determining whether or not to perform a function-based intra-prediction for the current block;
• performing intra-prediction for the current block for generating a prediction block of the current block;
• generating a residual block by subtracting the prediction block from the current block;
• and
• encoding the current block by encoding the residual block into the bitstream,
• wherein, when the function-based intra-prediction is performed for the current block, the performing intra-prediction comprises
• deriving a parameter for generating a function;
• performing intra-prediction by using the function based on the derived parameter;
• and
• encoding a prediction mode index indicating that the function-based intra-prediction is performed for the current block,
• wherein the prediction mode index is flag information signaled through a bitstream, having a first value indicating that the function-based intra-prediction is performed or a second value indicating that the function-based intra-prediction is not performed, and
• wherein the parameter for generating the function is derived based on at least one among a maximum sample value and a minimum sample value of previously reconstructed reference samples neighboring the current block, the maximum sample value being a value of a sample having a maximum value among values of the previously reconstructed reference samples, and the minimum sample value being a value of a sample having a minimum value among the values of the previously reconstructed reference samples.