Geometrical distortion in optical lens imaging is inevitable

and the polynomial coordinate transform algorithm is useful in rectification of image geometrical distortion

but it takes too much computational time to be applied in real time image processing systems when high order polynomials are employed on condition that complex nonlinear distortions are encountered. To decreases the computational complexity

an approximation algorithm is proposed in this paper

in which the image is firstly divided into rectangles

and then an appropriate first-order polynomial is used to approximate the high order polynomial within each rectangle. Based on the analysis of the radial distortion

which is considered to be the main kind of image distortion

a novel image partition method is presented to ensure minimal memory expense for model parameters. With the approximation algorithm two-third of the computational time is saved and the memory expense is also limited within a reasonable range. Experimental results indicate that the algorithm proposed in this paper is effective and valuable in the engineering applications.