Method for scaling and filtering images using discrete cosine transforms

(57) the summary image-processing method and equipment, So that the picture in a space domain can be displayed by using discrete cosine transformation in a frequency domain and scaling and the filtering effect may be attained in a frequency domain. It can be suitably operated in the picture in a space domain, the picture in a frequency domain can be reconverted to a space domain, or it can memorize, and it displays, and it can reproduce and can transmit to a remote place after that for re-use. The scaling (expansion reduction) technology which the present invention uses can be used for the picture expansion by interpolation, or the picture reduction by infanticide. In order to prevent the artifact in an infanticide process in infanticide, it is desirable to perform filtering operation in a frequency domain first. This filtering operation is equivalent-like mathematically as a result of the character of DCT conversion to the alignment tatami lump in a space domain. Also in any of the interpolation method and the method of thinning out, the hybrid contrary discrete cosine transformation which evaluates the independent variable of a series of cosine clauses is utilized with the value acquired by examining magnifications other than the usual sampling index increment size. As a result, picture points other than the picture point which consists of the image data of the origin in a space domain with approximation technology can be generated. It performs that this approximation technology displays a picture point on frequency space according to a series of clauses it can be considered over the range of the sampling index corresponding to the sampling index of the original image data that are continuous.