this module draws a scatterplot of the input image on a cie chromaticity diagram. this can be useful to visualise out of gamut/spectral locus colours and to aim for a certain illuminant during white balancing. the red cross indicates illuminant E (equal energy white, the white point of XYZ), the green line is the planckian locus, i.e. black body emission chromaticities.
in the background, the gamuts of rec709 (the smaller triangle ) and rec2020 (the larger triangle) are indicated as light gray shade.