SSIM calculation is incorrect for resolutions higher than 384 pixels on smaller dimension

[ssablin-meta]

Below code in ssim.c from IQA library forces input pictures to be downscaled and SSIM being computed on downscaled images instead of originals:

	const struct iqa_ssim_args *args = 0; /* 0 for default */
	int gaussian = 0; /* 0 for 8x8 square window - default */

    /* initialize algorithm parameters */
    scale = _max( 1, _round( (float)_min(w,h) / 256.0f ) );
    if (args) {

scale must be set to 1 to compute SSIM using original resolutions.