Improved Point-Line Feature Based Visual SLAM Method for Complex Environments

Traditional visual simultaneous localization and mapping (SLAM) systems rely on point features to estimate camera trajectories. However, feature-based systems are usually not robust in complex environments such as weak textures or obvious brightness changes. To solve this problem, we used more environmental structure information by introducing line segments features and designed a monocular visual SLAM system. This system combines points and line segments to effectively make up for the shortcomings of traditional positioning based only on point features. First, ORB algorithm based on local adaptive threshold was proposed. Subsequently, we not only optimized the extracted line features, but also added a screening step before the traditional descriptor matching to combine the point features matching results with the line features matching. Finally, the weighting idea was introduced. When constructing the optimized cost function, we allocated weights reasonably according to the richness and dispersion of features. Our evaluation on publicly available datasets demonstrated that the improved point-line feature method is competitive with the state-of-the-art methods. In addition, the trajectory graph significantly reduced drift and loss, which proves that our system increases the robustness of SLAM.

Detection and segmentation of erythrocytes in multispectral label-free blood smear images for automatic cell counting

In this work we propose an efficient approach to image segmentation for multispectral images of unstained blood films and automatic counting of erythrocytes. Our method takes advantage of Beer–Lambert’s law by using, first, a statistical standardisation equation applied to transmittance images, followed by the local adaptive threshold to detect the blood cells and hysteresis contour closing to obtain the complete blood cell boundaries, and finally the watershed algorithm is used. With this method, image pre-processing is not required, which leads to time savings. We obtained the following results that show that our technique is effective, efficient and fast: Precision of 98.47 % and Recall of 98.23 %, a degree of precision (F-Measurement) of 98.34 % and an Accuracy of 96.75 %.

Oil Spill Monitoring of Shipborne Radar Image Features Using SVM and Local Adaptive Threshold

In the case of marine accidents, monitoring marine oil spills can provide an important basis for identifying liabilities and assessing the damage. Shipborne radar can ensure large-scale, real-time monitoring, in all weather, with high-resolution. It therefore has the potential for broad applications in oil spill monitoring. Considering the original gray-scale image from the shipborne radar acquired in the case of the Dalian 7.16 oil spill accident, a complete oil spill detection method is proposed. Firstly, the co-frequency interferences and speckles in the original image are eliminated by preprocessing. Secondly, the wave information is classified using a support vector machine (SVM), and the effective wave monitoring area is generated according to the gray distribution matrix. Finally, oil spills are detected by a local adaptive threshold and displayed on an electronic chart based on geographic information system (GIS). The results show that the SVM can extract the effective wave information from the original shipborne radar image, and the local adaptive threshold method has strong applicability for oil film segmentation. This method can provide a technical basis for real-time cleaning and liability determination in oil spill accidents.

COUNTING SPERMA AKTIF MENGGUNAKAN METODE OTSU THRESHOLD DAN LOCAL ADAPTIVE THRESHOLD

Analisis sperma adalah pemeriksaan awal yang dilakukan pada kasus infertilitas pria, salah satunya adalah menentukan motiliti normal dan abnormal, yang dilakukan oleh ahli. Analisa sperma ini juga dapat dilakukan secara otomatis dengan berbantuan komputer, yaitu dengan cara mengambil per-frame video sperma kemudian dilakukan proses segmentasi. Pada proses segmentasi terdapat beberapa kendala antara lain data video yang diambil mempunyai intensitas yang berbeda, sehingga diperlukan beberapa metode segmentasi. Penelitian ini adalah membandingkan proses Otsu Threshold dan proses Local Adaptive Threshold (LAT), dengan proses preprosessing yang menggunakan segmentasi Otsu dan Local Adaptive, sehingga dari beberapa data frame video sperma yang disegmentasi akan diketahui segmentasi yang harus digunakan. Dari hasil penelitian didapatkan bahwa intensitas cahaya pada frame sperma yang dianalisis merata, dapat digunakan Otsu Threshold dan jika gambar sperma yang dianalisis intensitasnya tidak merata akan lebih bangus menggunakan Local Adaptive Threshold, dengan demikian untuk melakukan ekstraksi fitur lebih bagus, namun dari beberapa frame (bingkai) sperma yang diujicoba secara acak didapatkan akurasi yang lebih menggunakan proses otsu threshold yaitu 82% dibandingkan dengan menggunakan proses local adaptive threshold yaitu hanya 52%.

A LOCAL ADAPTIVE THRESHOLD APPROACH TO ASSIST AUTOMATIC CHROMOSOME IMAGE SEGMENTATION

In cytogenetics, karyotype analysis is used to assess the presence of genetic defects by visualization chromosomes structure from microscopic images. A key step in this process is image thresholding, used to detect and extract objects of interest from background, as it affects the performance of further processing steps in image analysis. In this paper, an adaptive local thresholding for Qband chromosome image segmentation is presented. A re-threshold process based on the Sauvola’s local adaptive technique is applied to extract chromosomes from background. Local adaptive histogram equalization is added between thresholding steps to enhance chromosome segments to reduce the chances of pixel misclassification. The proposed thresholding approach provides 93 % of precision, which is better than other similar approaches when evaluated on a reference image dataset.