More on the Fourier Transforms

Line Removal

To take high-resolution images in space, multiple pictures must be taken first, and then stitched together. However, the stitching process adds vertical and horizontal lines, which are prominent in the image below.

Stitched/composite image of the moon taken by the unmanned Lunar Orbiter V in 1967.

The lines caused by the stitching process are regular  and lie along one dimension, making them ideal artifacts to be removed through Fourier filtering. The following image shows the Fourier Transform and the filtered Fourier Transform.

Corrected image

The filtered Fourier Transform.

The Fourier Transform was filtered along the horizontal and vertical axes because the lines to be removed were vertical and horizontal. The filter proved to be effective and the image appears to be free of horizontal and vertical lines.