MAT-Based Thinning for Line Patterns

Abstract

Reducing branching effect and increasing boundary noise immunity are of great importance for thinning patterns. An approach based on medial axis transform (MAT) to obtain a connected 1-pixel wide skeleton with few redundant branches is presented in this paper. Though the obtained skeleton by MAT is isotropic with few redundant branches, however, the skeleton points are usually disconnected. In order to rend the merits of the MAT and avoid its disadvantages, the proposed approach is composed of distance-map generation, grouping, ridge-path linking, and refining to obtain the connected 1-pixel wide thin line. The ridge-path linking strategy can guarantee the skeletons connected, whereas the refining process can be readily performed by a conventional thinning process to obtain the 1-pixel wide thinned pattern. The performances investigated by branching effect, signal-to-noise ratio (SNR), and measurement of skeleton deviation (MSD) confirm the feasibility of the proposed MAT-based thinning for line patterns.

Pattern Reconstructability in Fully Parallel Thinning

“…The reason given is that the thinning templates and morphological structure elements adopted here are of a square form, and the reconstruction result depends strongly on the thinning result. In other words, the limit is due to the different eight-neighbor distances in a square grid as argued recently by Chen and Chao [40]. According to the equal six-neighbor distances in a hexagonal grid as reported by He and Jia [42], how to apply the hexagonal structure in the fully-parallel thinning algorithm design and the proposed approach could be a good topic and will be considered as our future works.…”

“…The MR increases with the accuracy of reconstructability, where MR = 1 represents that the pattern is reconstructed completely. Since the HDPs removed or not in a thinning iteration will significantly affect the thinning result and number of iterations (NI), the measurement of skeleton deviation (MSD) [40] and NI are also adopted for our performance evaluations. To evaluate the MSD, we can give an original thin line pattern P line , generate its thick-line pattern P thick by a thickening procedure [14] and perform the P thick by a thinning algorithm to obtain the skeleton result P skeleton .…”

“…This means that the three properties mentioned above are not easily maintained due to the effect of discrete metrics as investigated by the literature [31,38,39]. In order to render the advantage of the low boundary noise effect from the MAT and overcome the disconnected issue, a MAT-based thinning has been proposed by Chen and Chao [40]; who also argue a new challenge of "is it possible that the original line pattern can be completely restored with the thinned result?" Up to now, this issue is not easy for a conventional rule-based thinning algorithm since no reconstructable information is preserved, but the line connectivity during the thinning process.…”

“…Section 3 shows experimental results and comparisons. The measurement of reconstructability (MR) [12], the number of iterations (NI) and the measurement of skeleton deviation (MSD) [40] are used for analyses and discussions. The conclusions and future works are finally drawn in Section 4.…”

Research on the Improvement of EPTA Parallel Thinning Algorithm

“… The impact of external noise should be minimized (boundary noise immunity). At present, there are many thinning algorithms [9], [10], [11], [12]. However, many parallel thinning algorithms are applied in image processing.…”