Added assert for source image to be 8UC3, and changed returned isomap to 8UC4
Added assert for source image to be 8UC3, and changed returned isomap to 8UC4

At the moment, only TextureInterpolation::NearestNeighbour is adjusted to work

patrikhuber/eos,patrikhuber/eos,icyrizard/eos,icyrizard/eos,patrikhuber/eos,icyrizard/eos,ming81/eos