ADVANTAGES OF USING A DISTANCE TRANSFORM FUNCTION IN THE MEASUREMENT OF FRACTAL DIMENSIONS BY THE DILATION METHOD

A distance transform function is superior to sequential dilations in o btaining the perimeter fractal dimensions of two-dimensional objects. Eight connected outlines of objects were distance-transformed and the frequency distribution of the resulting image then used to obtain frac tal dimensions from Richardson plots. The measured dimensions of quadr ic and triadic islands were accurate. The method has three advantages over sequential dilations: (i) it is significantly faster, (ii) it gen erates more data points and (iii) it achieves a true radial dilation. The commonly-used 5 x 5 dilation element generates an octagonal dilati on and half the data points of the distance transform. A minor correct ion is suggested to compensate for distortions that result from overla ying a truly radial dilation on an orthogonal grid.