The interpolated high frequency sub bands and
the SWT high frequency sub bands have the same
size which means they can be added with each other.
The new corrected high frequency sub bands can be
interpolated further for higher enlargement. Also it is
known that in the wavelet domain, the low resolution
image is obtained by low pass filtering of the high
resolution image. In other words, low frequency sub
band is the low resolution of the original image.
Therefore, instead of using low frequency sub band,
which contains less information than the original high
resolution image, we are using the input image for
the interpolation of low frequency sub band image.
Using input image instead of low frequency sub band
increases the quality of the super resolved image