Image color replacement with numerical optimization

Numerical Optimization course final project

Jun 12, 2021

The topic of color replacement in images has interested me long before I started programming. Playing around with free tools and simple processing approaches (e.g. hue replacement in the HSV space) never felt “satisfying” in relation to what I was imagining when specifying the replacement colors - there’s always some fidgety part such as specifying thresholds which causes sharp edges or other strange-looking artifacts, or simply the replacement hues seem “off”. Various papers exist that do seem to do a good job (see this and this for some examples) and Photoshop naturally has an implementation, but when the time came to choose a topic for my final project in numerical optimization, I thought it was a good opportunity to take a shot at the problem myself. It’s a challenging problem and while the results are far from perfect, I’m pretty happy with how it turned out.

Some results

Original image: andersource

Experiments and musings