POCS-based method for digital image interpolation

A method for enlarging a digital input image comprising:

• defining a model image that is of the same size (pN×pN), (p>1) as a desired large image;
• selecting an initial estimate of an enlarged version of the input image, where the input image is of size N×N and the initial estimate image is of size pN×pN for a factor of p enlargement in both dimensions;
• transforming the N×N and pN×pN images by fast Fourier transform (FFT);
• replacing the first N×N FFT coefficients of the FFT of the initial estimate image with the N×N coefficients of the FFT of the input image;
• transforming the pN×pN by inverse FFT (I-FFT) of the intermediate estimate to transform it to the spatial pixel domain to obtain an intermediate estimate of the desired large image;
• correcting each pixel of the resulting pN×pN intermediate estimate image such that each pixel's variation from the corresponding pixel of the model image is within a predetermined lower and upper bounds, where these bounds vary according to pixel location;
• generating the next intermediate estimate;
• replacing the initial estimate by the resulting intermediate estimate;
• and
• repeating the above two cycles iteratively for K times and taking the final estimate resulting from K iterations as the estimate of the desired enlarged image.