Neural Computing for Online Arabic Handwriting Character Recognition using Hard Stroke Features Mining
Summary
The paper tackles the recognition of isolated online Arabic handwritten characters. Variable styles, writing speed and small diacritic differences between letters keep accuracy below what Latin and Chinese systems reach. The pipeline has four stages:
- Smoothing: pen trajectories are cleaned with a neighbour-weighted interpolation filter.
- Segmentation: each stroke is cut into smaller units called tokens. The method first decides whether a stroke is mainly horizontal or vertical by comparing its x-extent and y-extent. It then finds critical points: local maxima backed by monotone runs of points on both sides, with run length tied to the size of the pattern.
- Features: a small set of structural and statistical descriptors is computed per token and binarised. They include orientation, length, direction, midpoint and length relative to the parent stroke.
- Classification: a backpropagation multilayer perceptron with a modified sigmoid activation assigns the character class.
A stated design goal is to keep the number of tokens per character small and stable, so the classifier gets a fixed-size input. On characters from the OHASD benchmark, the system reports 98.6% average accuracy. This is competitive with earlier Arabic recognisers and suggests that careful segmentation can reduce the need for large feature sets.
Key points
- Data and result: the dataset is OHASD, split 70% for training and 30% for testing, with a reported average accuracy of 98.6%.
- Classifier settings:
- BP/MLP with a modified sigmoid activation;
- initial weights drawn from (−0.2, 0.2);
- learning rate 0.1;
- momentum 0.05;
- internal threshold 0.0.
- Critical points: a point counts as a local maximum only if y-values rise and fall monotonically over a window of about 0.05×N points on each side.
- Token-count stability (Table 5): the minimum token count occurs for 69% of characters, the most frequent count for 74%, and the maximum for 11%. Only Alef, Jeem, Ain and Yeh deviate from this pattern.
- Remaining errors: most come from look-alike pairs, notably initial-form Sad versus Seen. Delayed secondary strokes help separate pairs such as Seen/Sheen and Ain/Ghain.
- Earlier results for comparison:
- zoning plus EBPANN: 93.61%;
- rule-based projection profiles: 97.6%;
- ANN–PSO on the TMU dataset: 88.47%;
- fuzzy ARTMAP on IFN/ENIT: 94.72%.
Interesting ideas
- I1. Before choosing cut points, decide each unit's dominant axis by comparing its horizontal and vertical extents, then search for boundaries only along that axis; this adapts the segmentation rule to the shape of each unit instead of using one global rule.
- I2. A boundary is accepted only when supported by a consistent monotone run on both sides, with run length proportional to input size; this filters jitter and very short breaks without hand-tuned absolute thresholds.
- I3. The stability of a decomposition is measured as how often a character yields its most frequent token count, and that stability is treated as a goal in itself.
- I4. Features are expressed as ratios to the parent unit (token length as a percentage of stroke length), making them invariant to writing size.
- I5. Small detached marks are kept as separate delayed strokes but used together with the main body to separate near-identical letters, which is where the remaining errors concentrate.
For Mova
How these ideas could serve Mova, our small open language model — its files, stages and tests:
- I1 (tokens): the tokenizer could first classify a span's type (number, URL, hyphenated compound, ordinary word) and then apply a boundary rule specific to that type, logging which rule fired so each split stays explainable.
- I2 (learn): when mining self-induced repair rules, accept a candidate only if its evidence persists across a window of examples scaled to corpus size, which guards against rules triggered by a single noisy parse.
- I3 (learn): for silver data from several witness parsers, track how often each construction yields its modal number of nodes or frames, and flag low-stability constructions for teacher review.
- I4 (tree): parser features such as dependency distance could be normalised by sentence or clause length, so behaviour transfers between short school texts and long sentences.
- I5 (tokens): treat clitics, apostrophes and hyphens as attached secondary cues to the host word (e.g. 's vs s', it's vs its), and run error analysis on such confusable pairs to show which cue decided each tag.
Topics Semitic languages
Cite
Cite as Amjad Rehman. 2020. Neural Computing for Online Arabic Handwriting Character Recognition using Hard Stroke Features Mining. arXiv:2005.02171 · IJICIC 2021.
@misc{rehman2020neural,
title = {{Neural Computing for Online Arabic Handwriting Character Recognition using Hard Stroke Features Mining}},
author = {Amjad Rehman},
year = {2020},
doi = {10.48550/arxiv.2005.02171},
eprint = {2005.02171},
archivePrefix = {arXiv},
url = {https://doi.org/10.48550/arxiv.2005.02171}
}References
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