An image processing method and an image processing device, a display apparatus, and a non-volatile computer readable storage medium are provided. The method includes acquiring a first region and a second region adjacent to each other and having a common boundary in an image, a first brightness value of the first region being larger than a second brightness value of the second region; determining one or more brightness transition regions in the first region and/or the second region and at a side close to the boundary; determining one or more transition brightness values being smaller than or equal to the first brightness value and larger than or equal to the second brightness value; and setting brightness of each brightness transition region to be a corresponding transition brightness value.