Multiscale colour gradient for image segmentation

We present a new gradient model for colour video images. Video sources have the characteristic, either for transmission or for storage, to present a reduced bandwidth of colour components compared to that of brightness. Traditional multispectral gradient operators amplify the noise from the colour components and they are not very sensitive to colour edges. We propose an adapted vector gradient model to solve this problem and introduce the computation of the partial derivatives at different scales according to the resolution of each component. We show that a weighting function is necessary to control the relative influence of the colour and brightness components to obtain the multiscale colour gradient (MCG). The application of the MCG to colour edge detection illustrates the advantages of the proposed method. Finally, the MCG image is used for the segmentation by active contours of crystals in microscopic images of cement clinker (industrial application).