Nonlinear Contrast Enhancement of Medical Ultrasonic Image Based on Munsell´s Scale

Because of various reasons, medical ultrasonic image has a lot of noises. But after filtering processing, it will get blurry especially at the boundary of the region. Almost all of the traditional image contrast enhancement approaches can´t preserve the gray values and introduce distortion into the image. In this work, we introduce a nonlinear local contrast enhancement method. This method utilizes the Munsell value scale which is based on human visual perception. Munsell value scale partitions the gray scale into ten discrete subintervals. Then inside each subinterval, we consider the mean edge gray value as the point of the segmentation, and construct an appropriate function to mapping. In this way, the contrast of the image has been enhanced and the shades of the gray value are preserved. Experiment proves that it´s an effective medical ultrasonic image contrast enhancement approach.