Focused on the issues that circular domain extraction is not accurate and effective correction field angle can not reach 180 degrees in the vertical direction, Variable Angle Line Scan (VALS) method and Longitudinal Compression Cylindrical Projection (LCCP) method were proposed respectively. By changing the inclination angle of the scan line, the VALS method got coordinates of those cut points, then it filtered out invalid cut points coordinates and further got the parameters of the circular domain by using the Kasa circle fitting method. As for the LCCP method, it artificially bended the optical path of traditional cylindrical projection so that the light projected onto the infinity point could be projected back on the cylindrical surface, thus preserved the image information effectively. The comparison with two known methods named longitude-latitude mapping and Mercator mapping proves the effectiveness of the proposed algorithm in weakening the blurring effect due to stretching caused by the edge of image correction. The result looks more nature.
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2015, Vol. 35 
