1. A method for processing an input ultrasonic image by locally adjusting a gray scale intensity of the image classified as a non-feature region, comprising: using a processor to perform the steps of: a) dividing the input image into blocks, and computing a gray mean of each blocked image, Mean block; b) setting different gray-scale adjustment coefficients R adjust, based on the different gradient values of various pixels in the input image; and c) computing an adjusted gray scale intensity I adjusted to produce a local gray-scale adjusted image I adjusted=Mean block +(Iin −Mean block)* R adjust, where Iin represents the gray scale intensity of the input image; d) computing a mean image represented by its gray scale intensity I mean for the local gray-scale adjusted image I adjusted by using a neighbor domain of each pixel thereof with variable size; e) determining a compensating pixel and its respective compensating amount based on the mean image I mean; and f) adding the compensating amount for each compensating pixel into the local gray-scale adjusted image I adjusted, to remove the speckles from the non-feature regions; wherein the compensating pixel means a pixel for which an image difference I diff obtained by subtracting the mean image I mean from the local the gray-scale adjusted image I adjusted is greater than a predetermined value; and the compensating amount for the respective compensating pixel is multiples of the respective difference I diff.