Abstract: A technique is proposed to eliminate the illegible effect by the binarization with self-adaptive thresholding according to the features of defocused QR code image.The corner points are initially located by contour search algorithms，and a QR code image is rebuilt from a distorted one by using a double tangents method designed to approximate the right-bottom point with double inverse perspective transformations.A novel self-adaptive grids generation algorithm for sampling is designed to generate the final code image.Experimental results show that our method is simple and workable，especially for defocused and distorted QR barcode images.