Image Color Cube Dimensional Filtering and Visualization

W e cal l RGB cube the three dimensional representation of the colors of a digital image in RGB space. This cube simply shows the (R,G,B) color points which actually appear in the digital image. This visualization has, however, two main defects: it does not show the real RGB histogram. The difference is that in the color cube each point is plotted with its own color, while in the RGB histogram it has a grey level representing the number of pixels in the image having this color value. It is of course impossible to display these two features simultaneously. The perspective views, which are most used, hide the real dense cloud, which is surrounded by a fume of isolated color points. These isolated color points, mainly due to the image noise and to compression artifacts, make an opaque obstacle to the perspective view of the cloud. Perspective views remain nonetheless the classic visualization tool, because the cube occupation by the color points of a natural image is far from complete, as it can be seen in the following example: