1. A method of radiographic image enhancement for an unsharp masking processing, comprising the steps of dividing an image into a plurality of local images; obtaining an unsharp image by averaging neighboring pixel values at local regions of the original image; subtracting the unsharp image from the original image to produce a sharp image; and adding an original image at a desired ratio to the sharp image to create a processed image, wherein said averaging step comprises effecting a weighted mean arithmetic operation of the pixel values of the local regions based on a weight coefficient which is determined in accordance with a monotonically decreasing or increasing function with respect to a density difference between a central pixel value and neighboring pixel values.