G-quadtree: A hierarchical representation of gray-scale digital images

We propose G-quadtree as a hierarchical representation method for gray-scale digital images. G-quadtree is an extended quadtree each leaf of which holds a multi level-value. An algorithm constructing a G-quadtree from the array representation of a gray-scale image is described, implemented and tested. The algorithm is established in such a way that the conventional binary array-to-quadtree conversion algorithm is applied to each bit of array elements repeatedly in descending order of significance. Space efficiency analysis reveals that G-quadtree representation is sufficient in a particular application to a color coding of macroautoradiography of rat brains.