Abstract: Stitched panoramic images mostly have irregular boundaries. In order to obtain standard images with rectangular boundaries, most panoramic stitching algorithm generally prefers to crop the images directly at the expense of decreasing the vision of panoramic images. An approach of rectangling images via sub-pixel seam carving has been proposed. It uses cubic spline interpolation and image completion to smooth the irregular boundaries. Taking the value of normalized difference between the smoothed boundaries and the expectable rectangular boundaries of the images as scale factor, it stretches or compresses each pixel on optimal seam in the range of 0-1 pixels and translates other pixels on one side of the seam repeatedly until the desirable boundaries are reached. Experimental results on a number of panoramic images show that the proposed method can achieve good results especially when the boundaries are very concave.