Inter prediction mode-based image processing method and apparatus therefor

An apparatus for processing an image based on an inter prediction, comprising:

• a bi-directional predictor generation unit for generating a bi-directional predictor of each pixel of a current block by performing a bi-directional inter prediction based on a motion vector of the current block;
• a motion vector derivation unit in a unit of pixel for deriving a first motion vector from a window area of a specific size in a first reference picture for a current pixel, and deriving a second motion vector from a window area of a specific size in a second reference picture for the current pixel;
• a first predictor and second predictor derivation unit for deriving a first predictor for the current pixel using the first motion vector, and deriving a second predictor for the current pixel using the second motion vector;
• and
• a third predictor generation unit for generating a third predictor of each pixel of the current block by performing a weighted sum of the first predictor and the second predictor.