古蹟石材影像辨識系統開發研究

A Study of an Image Recognition System for Stone Materials on Historical Sites

在漢式建築中石材因環境影響所受到的損壞時間較長，相關破壞偵測方法及研究分析就顯得薄弱，實務上造成石材修復或是置換的過程中，使用了不同種類或是不同礦源之石材，對於古蹟的維護形成負面的影響。有鑑於此，研擬「古蹟石材影像辨識系統」，提供古蹟石材種類及礦源產地之辨識功能。本研究首先建置由廈門大方進出口貿易有限公司2013年出版之「天然石材樣品集」396個石材樣本資料庫，其種類涵蓋花岡岩、變質岩、玄武岩、安山岩及砂岩等，紀錄其石材種類之礦物組成比例及礦源產地。設計之辨識流程為自古蹟現場以高解析度攝影之非破壞性模式取得石材之影像資料，經影像處理技術判釋其礦物之組成比例，再與資料庫之石材樣本資訊進行分析比對，進而判釋其可能之石材種類及礦源產地。本研究以資料庫中之78個花岡石樣本為研究對象進行本系統影像判釋符合度測試。研究成果顯示，當石材礦物組成比例與資料庫樣本進行比對後，吻合度大於90%時，其礦源產地判斷均符合；但若小於90%時，則無法準確判斷其礦源產地，僅能縮小其可能範圍。因此，取得較佳之影像分類結果，才能更有效進行礦源產地之判斷。不過，本系統之開發已能提供古蹟維護單位對於石材種類及礦源產地初步判斷的能力，應能有效改善古蹟修復過程中錯用石材之情形發生。

In the Chinese-style architecture, building stone becomes damaged due to environmental impacts over prolonged exposure to the elements. However, the relevant damage detection methods, research and analysis are weak. In actual practice, stone repair or replacement process may use different types of stone or different source quarries. Different stones have a negative impact on the overall preservation of monuments. In view of this, the“Historic Stone Image Identification System”was developed to provide an identification of historical stone types and help identify the origin of the stone resources. This study first built a database of 396 stone samples from the“Natural Stone Sample Set”published by China in 2013. The types of stone samples include granitoids, metamorphic rocks, basalts, andesite and sandstones, - recording both the mineral composition of the stone types, and their origins. This non-destructive identification process acquires image data of the stone using high resolution photography at the site of the historic monument, and determines the mineral composition for comparison with the stone sample information from the database. The interpretation makes possible identification of stone types and origins. In this study, 78 samples of Huagang Stone in the database were taken as the research materials to test the conformity of the system. The research results show that when the proportion of stone minerals is compared with the database sample, is the match is more than 90%, then the unknown can be sourced to the site of the quarry, but if it is less than 90%, the source area cannot be accurately determined, and only the possible range identified. In summary, better image classification results can be used to more effectively determine the origin of building stones. However, the development of this system is able to provide the architectural conservators with the ability to make initial judgments on the type of stone and source of the stones used in a monument in the process of monument restoration.