Researchers remove colour cast from underwater photos
Two researchers are using machine learning to remove the blue or green tint from underwater images - with impressive results.
Underwater images have a strong blue or green cast. This is because the wavelengths of blue and green penetrate much deeper than those of red. The problem can be alleviated with artificial lighting and filters, but this requires considerable effort and does not work in every situation.
Researchers Derya Akkaynak and Tali Treibitz have developed a new method called Sea-Thru to extract the colours from blue-green underwater photos that they would have without water. The results look pretty impressive.
According to Derya Akkaynak, this is a physically accurate correction and not just colour cosmetics, as would be possible in Photoshop. They photographed the same motif many times with slight variations, always including a colour map. This material was used as training for machine learning.
The degree of discolouration depends on the distance. In a complex three-dimensional structure such as a reef, there are countless different distances from the camera and each pixel must be calculated separately.
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