ENHANCEMENT OF 3D SURFACE RECONSTRUCTION OF UNDERWATER CORAL REEF BASE ON SIFT IMAGE MATCHING USING CONTRAST LIMITED ADAPTIVE HISTOGRAM EQUALIZATION AND OUTLIER REMOVAL

Abstract

ENHANCEMENT OF 3D SURFACE RECONSTRUCTION OF UNDERWATER CORAL REEF BASE ON SIFT IMAGE MATCHING USING CONTRAST LIMITED ADAPTIVE HISTOGRAM EQUALIZATION AND OUTLIER REMOVAL aPulung Nurtantio Andono, bRicardus Anggi Pramunendar, cCatur Supriyanto, dGuruh Fajar Shidik,e I Ketut Eddy Purnama, fMochamad Hariadi a,b,c,dFaculty of Computer Science, Dian Nuswantoro University Jalan Imam Bonjol, No. 207, Semarang 50131, Indonesia e,fFaculty of Industrial Technology, Dept. of Electrical Engineering, ITS, Surabaya, Indonesia Email: a pulung@research.dinus.ac.id Abstrak Penelitian ini menggambarkan peningkatan kualitas rekonstruksi 3D permukaan terumbu karang bawah laut menggunakan sistem kamera stereo. Algoritma Contrast Limited Adaptive Histogram image Equalization (CLAHE) diusulkan untuk meningkatkan kualitas citra bawah laut tersebut, karena menurunnya kualitas citra bawah laut dapat disebabkan oleh penyerapan dan hamburan sinar matahari. Dalam mengembangkan rekonstruksi 3D permukaan bawah laut, pasangan citra stereo diekstrak secara manual dari rekaman video yang diperoleh, yang kemudian dilakukan proses pencocokan citra stereo menggunakan algoritma SIFT. Kelebihan algoritma SIFT tersebut adalah tahan terhadap perubahan skala, transformasi, dan rotasi dari sepasang citra tersebut. Banyaknya matching point antar 2 citra stereo dijadikan ukuran untuk mengetahui kinerja CLAHE terhadap algoritma SIFT. Hasil penelitian menunjukan bahwa penggunaan CLAHE dan outlier removal mampu meningkatkan jumlah matching point sebesar 56%. Keberhasilan CLAHE tersebut perlu diujikan ke beberapa algoritma matching point yang lain. Perbandingan beberapa algoritma matching point yang menerapkan CLAHE dapat membuktikan bahwa CLAHE sangat cocok dalam meningkatkan kinerja algoritma matching point dan rekonstruksi permukaan 3D citra bawah laut. Kata kunci: Rekonstruksi 3D, Citra Bawah Laut, SIFT, CLAHE. Abstract This research describes an enhancement of 3D Reconstruction coral reef images using stereo camera system. Contrast Limited Adaptive Histogram image Equalization (CLAHE) algorithm was proposed to enhance the image quality in preprocessing area, since the quality of underwater images degrades by the absorption and scattering of light. To develop a 3D-representation of the seafloor, image-pairs were first extracted from the video footage manually, then corresponding points are automatically extracted from the stereo-pairs by SIFT matching algorithm, which is invariant to scale, translation, and rotation. Number of matching points is used to evaluate the performance of SIFT with and without CLAHE. As a result, the promising techniques provides better 3D reconstruction details of coral reef imagesin total, the combination of CLAHE and outlier removal performs the enhancement for 56%. For further, CLAHE need to be performed to other image matching techniques. The comparison of different image matching techniques with and without CLAHE can prove that CLAHE is appropriate as image enhancement method for image matching and 3D surface reconstruction. Key words: 3D Reconstruction, Underwater Image, SIFT, CLAHE.