臺灣博碩士論文加值系統

日前的社會治安日趨敗壞，國內槍擊事件、擄人/車勒索事件、搶劫等事件日愈頻繁，因此安檢的重要性與需求量將日愈重要。目前有許多縣市開始重視道路攝影的需要，已多次藉由所拍攝得的視訊，針對可能歹徒的車輛做追蹤且掌握其行跡並進而破案。從影片中找出可疑車輛需要非常專心且花費大量的時間進行，因此需要一套可以從影片中自動找出車牌位置的系統。

為了滿足上述的需求，本論文利用影像處理的技巧發展出一套適合警方使用的車牌偵測系統。雖然目前攝影機解析度可達到640*480，但是為了減少影像的儲存容量，通常使用320*240的解析度以及較差的影像品質儲存影像。因此本論文針對低解析度的影像發展。在論文中對日間以及夜間的戶外影像做處理，利用變異數計算以及型態學的Bottom-Hat、Top-Hat轉換的技術將車牌部分偵測出。本研究使用12小時的日間連續影像以及2小時的夜間連續影像測試，在日間的部分，車牌定位成功率為93.74 %，false alarm rate為1.17%。在夜間的部分，車牌定位成功率為78.57%，false alarm rate為15.58%。

The amelioration of social order in our country caused by gun-fire event, extortion of car and human hostage, and robberies has greatly influence the society. This crisis has made security check and video surveillance become more important. Currently, the installation of video surveillance cameras is getting popular on the streets of many counties and cities. The recording of the passing vehicles and their license plate in these videos have successfully help the police solving many cases including hit-and-run, extortion of human hostage, etc.. However, search the video to extract and record the license plate (LP) of the suspected vehicles needs a lot of effort and time. This tedious work sometimes decreases the willingness and efficiency of the police in pursuing the criminals which places a great threat to our society. It''s obvious that the police needs an automatic system to extract the license plate from the video for them.
In view of the above demand, we propose utilizing the techniques of image processing and develop an automatic LP detection system to suit the police department''s urgent need. Although most of current video cameras are equipped with a resolution of 640x480, to save the storage space, videos are usually taken at low resolution (320x240) and saved at high compression ratio. This available low resolution and poor quality data not only distinguish the research in this thesis from that of the other LP detection system, it also puts a great challenge to our design. In this thesis, we deal with both daytime and night-time video. On the basis of local variance of the image and techniques of morphology (e.g. bottom-hat, top-hat), method which detect location of the license plate was successfully developed. Videos of 12-hour daytime and 2-hour night-time taken by police department from several street scenes are used to evaluate the system performance. The results show that the LP detection rates are 93.74% and 78.57% for the daytime and night-time, respectively. Their corresponding false alarm rates are 1.17% and 15.58%.

中文摘要 i
英文摘要 ii
誌 謝 iii
目 錄 iv
圖 目 錄 vi
表 目 錄 viii

第一章 緒論 1
1.1研究背景 1
1.2研究動機 2
1.3車牌規格及種類 3
1.4 論文架構 4
第二章 文獻探討 6
2.1 相關研究 6
2.2 車輛偵測技術 6
2.3 車牌定位相關研究 7
2.3.1 邊緣特性以及高對比性 7
2.3.2顏色特性 9
2.3.3 物件分析以及車牌在影像中的強烈特性 11
2.3.4 車牌定位方法優缺點 12
2.4 研究目的 14
第三章 系統架構 17
3.1基本原理 17
3.1.1 二值化處理 17
3.1.2 平滑濾波器 18
3.1.3 邊緣偵測(Edge detection) 20
3.1.4 型態學 23
3.2車牌定位系統架構 26
3.2.1 Preprocessing 26
3.2.2車牌區塊確認 29
3.2.3 日間演算法 32
3.2.4 Localization of License Plate 33
3.2.4.1 Bottom-hat transformation、morphological gradient &二值化 35
3.2.5 License Plate Extraction 37
3.2.6 Character Region Extraction 41
第四章 夜間演算法 44
4.1 亮度統計 45
4.2 Night algorithm with variance and bottom-hat transformation for enough light 46
4.2.1 Image Enhance 47
4.3 Night Algorithm with Top-Hat transformation for lack of light 48
第五章 實驗結果 52
5.1 測試影像 52
5.2 日間影像的結果 52
5.2.1 日間錯誤影像 59
5.2 夜間影像的結果 61
5.2.1 夜間錯誤影像 62
第六章 結論及未來研究方向 64
6.1 研究成果 64
6.2 未來展望 64
Reference 66

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