1. A method of processing an input image, the method comprising: obtaining a first blurred image and a second blurred image having different blurring degrees, from the input image; estimating illuminance of an image generated by combining the first blurred image and the second blurred image; generating a dark region amplified image from the input image by amplifying pixel values of a dark region in the input image; generating a bright region conserved image from the input image by maintaining pixel values of a bright region in the input image; applying weights to the dark region amplified image and the bright region conserved image, respectively, according to the estimated illuminance; combining the weighted dark region amplified image and the weighted bright region conserved image to generate a final image in which occurrence of a halo artifact effect is reduced; and outputting the final image for display.