Dial Correction Method of Circular Instrument Based on Perspective and Affine Transformation

A dial correction method based on perspective and affine transformations for pointer instrument reading recognition using the angle method is proposed to address the error caused by image capture angles. Firstly, Hough circle detection is used to locate the circular instrument and remove background interference. Then, Canny edge detection and least squares method are applied to detect the contour of the instrument dial, and the inner contour is used to extract the dial area. Finally, to correct the distortion of the circular dial into an ellipse due to different shooting angles, projection transformation and affine transformation are utilized to correct the distorted instrument dial. The experimental results show that the dial correction method studied in this paper can achieve the goal of restoring the horizontal alignment of instrument dials captured at different angles.