Extracting color information from lit regions to adjust shadow regions, HSV space If I wanted to match the color of a shadow region to the color it is supposed to be in the lit region, would this, purely color information, be preserved in the hue of the HSV space of the image?
Probably not – the observed color of a material is a result of the composition of light that illuminates the spot, and what of that the material reflects.
For example, if you have a bright light with strong red/yellow component (&quot;warm light&quot;), and you have ambient/scattered light at a lower level that's more or less white, then a green spot in the bright area will have a different tint than in the shadow.
(note: a shadow isn't perfect darkness, otherwise everything there would be the blackest of blacks.)
So, you need have a model of at least your main light and how ambient light, eg. from scattering that on a not-quite-perfectly-white wall, changes the spectrum of that, and of the actual color of the material (which you can't see in either, unless one of these is a reference white light source...).