| 研究生: |
蘇義明 Su, Yih-Ming |
|---|---|
| 論文名稱: |
中文信封文字辨識與雜訊文字筆劃擷取 Recognition of Chinese Postal Addresses and Stroke Extraction from Noisy Characters |
| 指導教授: |
王駿發
Wang, Jhing-Fa |
| 學位類別: |
博士 Doctor |
| 系所名稱: |
電機資訊學院 - 資訊工程學系 Department of Computer Science and Information Engineering |
| 論文出版年: | 2003 |
| 畢業學年度: | 91 |
| 語文別: | 中文 |
| 論文頁數: | 142 |
| 中文關鍵詞: | 地址辨認 、筆劃擷取 、地址切割和字元辨認 、前處理 、影像擷取 |
| 外文關鍵詞: | address recognition, stroke extraction, image acquisition, address segmentation, character recognition |
| 相關次數: | 點閱:98 下載:4 |
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處理中文字的一些問題可從兩個觀點來考慮,其中包含以系統實作的觀點來完成地址辨認和以技術改善的觀點來完成筆劃擷取。這些考慮可提供以科學和工程的角度來研究中文字元的處理。首先,為了完成一套實作系統並考慮其實際的問題,我們發展一套郵件分揀系統,並根據中文字的處理以改善郵件處理的效率。這套系統以辨認中式信封上的縣市名和路街名,分別提供兩個不同的分揀階段,包含郵政中心和支局的分揀,而這套即時辨認系統組成幾個模組:影像擷取、前處理、地址切割和字元辨認等模組。在這些模組中,我們常用一些探索和嘗試錯誤的方法來解決一些實際的問題,包含處理低品質的影像、要求系統處理的速度和有效性以及系統操作的穩定性。從實驗觀察,我們完成第一階段縣市名的辨認,並以每小時分揀八千筆信封,其正確率為75.6%、錯誤率為0.92%和拒絕率為23.48%。再者,我們也完成第二階段路街名辨認,其正確率為71.6%、錯誤率為1.05%和拒絕率為27.35%。
對於中文字處理在技術改善方面,我們也提出一個嶄新的筆劃擷取方法。以兩種方向性濾波的技術擷取雜訊中文字元的筆劃線段。對於使用結構分析作中文字辨認系統,此強健的擷取方法是必要的。此濾波技術分別使用兩個不同濾波核心,包含Gabor和SOGD函數。而且,為了擷取任意方向的筆劃線段,我們估算筆劃的方向是藉由發現筆劃線段在濾波輸出中有最大的能量反映。然後,我們利用學習式的特徵點確認方法,以減少字元結合點定位的不確定性,以取代特定性規則式的技術。從實驗結果觀察,我們所提出的筆劃線段擷取方法,不僅提供免除於結合點的失真和造成虛假的分支,而且容許擷取筆劃線段時,有雜訊存在於中文字元。再者,學習式的技術有助於提供一般性學習知識的能力對字元特徵點的瞭解且決定特徵點的型態,此方法優於規則式的技術對於字元特徵點的偵測。最後,我們使用SOGD濾波技術進一步分解一個中文字元進入不同方向的筆劃線段,同時我們也比較辨認的結果分別來自分解和非分解的字元處理,其中分解字元的處理有助於提高辨認率約17.31%。
Some problems of processing Chinese characters are considered according to the aspects of the system implementation for address recognition and technique improvement for stroke extraction. The considerations give the scientific and engineering views for the research of character processing. Firstly, in order to take into account system implementation and practical issues, a mail-sorting system based on Chinese character processing is developed to highlight practical challenges for improving the effectiveness of automatic mail handling. The developed system is based on recognizing city/county and road/street names on the Chinese mail envelopes for two different sorting stages in mail sorting centers and branches, respectively. The proposed real-time system consists of the following modules: image acquisition, preprocessing, a new approach named curve-mapping segmentation, and neural network-based character recognition. Some heuristic approaches within these modules are adopted to improve some practical problems, including the processing of low-quality images, the demand of the processing speed, the robustness of system operation, and the effectiveness of system processing. From experimental observations, the first mail-sorting stage based on recognizing city/county names was achieved to sort 8000 mail pieces per hour with an accuracy rate of 75.6%, an error rate of 0.92%, and a rejection rate of 23.48%. Furthermore, the second mail-sorting stage based on recognizing road/street names was achieved in the error rate of 1.05%, the average accuracy rate of 71.6%, and the rejection rate of 27.35%.
To consider technique improvement for Chinese character processing, we also proposed a novel stroke extraction method based on two directional filtering techniques for extracting reliable stroke segments of noisy and degraded Chinese characters. The robust stroke extraction method for Chinese characters is essential to off-line character recognition systems, which depend on stroke structure analysis to function. The filtering techniques use two different filter kernels, including Gabor and second-order Gaussian derivative (SOGD) functions. Moreover, to extract the stroke segments along an arbitrary orientation, the orientation of stroke segments is estimated by finding their maximal power responses in filter output. Then, a learning-based feature-point identification technique is used to eliminate the uncertainty of junction positioning, instead of using specific rule-based techniques for stroke-segment merging. From experimental observations, the proposed stroke-segment extraction approach based on the directional filtering techniques can not only provide immunity against the junction-distortion and spurious-branch problems caused from a thinning-based process, but is also insensitive to shape degradation and noise. Moreover, the learning-based technique is capable of generalizing the learning knowledge to determine the types of feature points, rather than the rule-based techniques for detecting feature points. Finally, the SOGD filtering-based technique is utilized to decompose the Chinese characters into a set of stroke segments. Meantime, comparing the recognition performance from the decomposition process with that from non-decomposition process reveals that the process of decomposing Chinese characters is very helpful for improving recognition performance about 17.31% in test character set.
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