Single image super resolution with guided back-projection and LoG sharpening

Single image super resolution requires approximation of high frequency information that was not captured in the available low resolution image. The process may result in an image that differs significantly from the original scene if no constraints are imposed. Iterative back-projection is one method used to guide the resolution enhancement process. This paper augments the iterative back-projection with edge sharpening of the error image and guided filtering to improve the high frequency content of the image. The algorithm is tested on 27 RGB colour images including the 24 images from the Kodak lossless true colour image set. The results are compared to those obtained using bicubic interpolation, wavelet zero padding and the established edge guided method. In the average results from the 27 images, the proposed method is observed to have an improvement of 0.9% over bicubic interpolation, 5.8% over wavelet zero padding and 7.5% over new edge directed Interpolation in terms of peak signal to noise ratio. The corresponding improvement in terms of structural similarity index are 1.1%, 3% and 6.8% respectively. In addition, the proposed method has the effect of suppressing spurious colours in the enhanced image.