Runlength Statistics

Consecutive pixels along a selected orientation tend to have the same intensity in a smooth region while their values change significantly in rough regions. A run is defined as a string of pixels with same value, aligned in a given orientation. The run length information is collected typically by using the orientations 0 — 0°, 45°, 90°, and 135°. For each orientation 0, the number of runs with a length of m pixels at gray scale k is computed to form the run-length histogram ^(m, k). A smooth structure produces more runs at large values of m than a rough structure. In striated tissue, long runs occur in the direction of the striation, whereas the orthogonal direction yields numerous short runs. Texture can be quantified by analyzing the run-length histograms for different orientation. A common metric, the run percentage is given by

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