Stereo image processing is a mostly used when mastering to extend the stereo base to make the mix sound “wide.”
A “widening” effect is achieved by distributing a number of frequency bands from various middle frequency ranges to the left and right channels.
This ultimately increases the perception of stereo width without the mix sounding unnatural.
However, phase issues may occur when working with a stereo image processor. Alway’s be sure to monitor your phase correlation while using this type of effect. Mixes out of phase will translate poorly when summed to mono.