sod_img sod_gaussian_noise_reduce(sod_img input);
Gaussian Noise Reduce. That is, apply 5x5 Gaussian convolution filter, shrinks the image by 4 pixels in each direction, using Gaussian filter. This works only on grayscale images. If you want to convert the colorspace of your input picture to the gray color model, call sod_grayscale_image() or sod_grayscale_image_3c() before.
Processed image is returned in an instance of the sod_img object. if something goes wrong during processing, then an empty image is returned via sod_make_empty_image(). Once done, you must release the memory allocated to this object via sod_free_image() to avoid memory leaks.