  Data compression is a method of improving the efficiency of transmission and
storage of images. Dithering, as a method of data compression, can be used to
convert an 8-bit gray level image into a 1-bit / binary image. Undithering is
the process of reconstruction of gray image from binary image obtained from
dithering of gray image. In the present paper, I propose a method of
undithering using linear filtering followed by anisotropic diffusion which
brings the advantage of smoothing and edge enhancement. First-order statistical
parameters, second-order statistical parameters, mean-squared error (MSE)
between reconstructed image and the original image before dithering, and peak
signal to noise ratio (PSNR) are evaluated at each step of diffusion. Results
of the experiments show that the reconstructed image is not as sharp as the
image before dithering but a large number of gray values are reproduced with
reference to those of the original image prior to dithering.
