1. An ultrasonic diagnostic apparatus comprising: a multi-resolution decomposition computer-implemented processor configured to perform a multi-resolution decomposition on ultrasonic image data so as to obtain first image data corresponding to a low-band signal component and at least one of second image data corresponding to a high-band signal component; a reduction computer-implemented processor configured to perform a regional maximum value reduction process of reducing a regional maximum value lower than a first level and a regional minimum value reduction process of reducing a regional minimum value higher than a second level on the first image data and the at least one of the second image data; and a reconstruction computer-implemented processor configured to perform a multi-resolution reconstruction by using the first image data and the at least one of the second image data having been subjected to the regional maximum value reduction process and the regional minimum value reduction process so as to create a reconstruction image; wherein the reduction computer-implemented processor repeats the regional maximum value reduction process including a morphological dilation process and stops the regional maximum value when the first image data and the at least one of the second image data are converged, and determines when the first image data and the at least one of the second image data are converged for each image subject to the multi-resolution decomposition based on a comparison between a member image and a process image, and to change a number of times of executing the morphological dilation process for each image based on determining when the first image data and the at least one of the second image data are converged; and the reconstruction computer-implemented processor performs the multi-resolution reconstruction by using the converged first image data and the converged at least one of the second image data.