New Approaches for Highly Accurate Detection of Scaling-Change Center Positions and for Precise Scaling Correction of Scaling-Changed Images

〈Summary〉 This paper describes a new approach for accurately detecting scaling-change center positions of slightly scaling-changed images and also proposes a new technique for correcting the scaling changes. These approaches utilize the phase difference spectrum analysis approach for detecting image shifts and the technique for detecting scaling factors, without iterative approximation calculation. In experiments, three types of image patterns were used. When the position is within a few ten pixels from the image center, the detection accuracy of the scaling-change center position is 2.2 pixels on average and as high as 1.1 pixels, excluding errors for scaling-factor changes below ±0.6%. The correction accuracy for scaling factors is almost completely independent of the scaling-center position and is about 0.0004 on average. The pixel displacement of the corrected image from the reference image is about 0.012 pixels on average when the scaling-change center position is within a few ten pixels from the image center. From these results, it is clear that the proposed approaches, despite their simplicity, make it possible to detect scaling-change center positions for scaling-changed images and to correct the images with high accuracy and reliability.