Some calibration points need to be placed in the shooting region by the traditional image correction, and then the image is corrected based on the knowledge of the computer vision. A novel algorithm without a calibration point is proposed for image correction. Four virtual calibration points are constructed with the help of some information on camera's internal physical structure and the Direct Linear Transformation (DLT) algorithm, and the correction coefficient is calculated by means of these virtual calibration points. According to the correction coefficient, the true shape of an object is obtained. The new algorithm is tested by correcting six images. Furthermore, the reasons for a micro-error are analyzed. Meanwhile, some methods for decreasing error are presented.