As an outline of an object in images, there are two kinds of edges, the one is an edge of the natural image that changes smoothly and another one is a steep edge of the character and the CG image. However, since the previous enlargement method processed regardless of the type of edges, the noises, such as jaggy, dotage, ringing, had happened in the enlargement image. In this paper, an enlargement method to extract the edges of a character and CG image among two types of images is proposed. Here, the concentration difference of 4 pixels near the interpolation point is used. In a smooth concentration domain with a less concentration difference, it interpolates smoothly with linear interpolation. Conversely, in the domain with a remarkable concentration difference, the position and direction of edge were presumed from the concentration difference, and the concentration value was computed from the distance of interpolation and edge. Moreover, the presumed edge was pursued to the neighboring domain, and it connected smoothly by changing inclination. The proposal method is compared with the previous method using visualevaluation and numerical evaluation, and as a result, validity of the proposal method is clarified.
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