【作者】 王本强；

【导师】 彭延军；

【作者基本信息】 山东科技大学 ， 计算机应用技术， 2009， 硕士

【摘要】 犯罪现场留下的足迹图像,为法庭提供了有价值的证据,是公安部门侦破过程的一个重要环节。现场足迹的模糊性、残缺性以及光照不均等特点给快速、准确地进行足迹图像的分析与匹配提出了很大的挑战。足迹识别算法大都需要进行调整或者分类,影响了识别的速度与精度。刑事案件侦破需要足迹识别算法针对足迹图像的特点,能够快速而且准确地识别出待比对图像。针对现场足迹的特点,本文提出并实现了基于Canny的足迹边缘检测算法以及基于形状上下文的足迹比对算法。首先对原始的足迹图像进行灰度转换;然后以Canny算子为基础,使用高斯平滑抑制噪声,在二维高斯偏导卷积得到梯度边缘方向后由非极大值抑制和动态阈值边缘连接实现足迹边缘检测;最后对边缘进行采样后建立极坐标系得到现场足迹每个点的形状表达,并进行归一化处理,通过计算检索足迹和待比对足迹的形状上下文距离获取其相似度,实现足迹图像的比对与识别。基于形状上下文的足迹比对算法满足平移,旋转,缩放的不变性,提高了现场足迹比对的准确度、效率。通过实验及实验结果的分析,验证了基于Canny的现场足迹边缘检测算法不仅能够抑制噪声,而且能有效地保持边缘。更多还原

【Abstract】 Shoeprints found at crime scenes provide valuable forensic evidence, and is also an important part in judicial investigations. Due to the characteristics of vagueness, incompleteness and uneven brightness, it is a great challenge to analyze and match among shoeprints. The speed and precision of recognition are affected because previous shoeprints recognition algorithms are mostly needed to be classified or to be adjusted. The detection of criminal cases requires that recognition algorithm must aim to the characteristics of shoeprints and be able to quickly and accurately identify the matched shoeprints.In the light of the characteristics of shoeprints, edge detection based on canny operator and matching algorithm based on shape context are proposed in this paper. Firstly make a gray-scale conversion to original shoeprint; then on the basis of canny operator, suppressing noise using Gaussian mask, calculating gradient and edge direction with convolution of derivative of two-dimensional Gaussian, non-maximum suppression and dynamic threshold and linking edge, implement edge detection of shoeprints; finally establishing polar coordinate system to obtain shape representation of every sample point which are sampled from the detected edge, normalizing, the measurement of similarity is got by computing the distance between the shape context of query shoeprint and that of matched one, achieve matching and identification of shoeprints. The proposed matching algorithm based on shape context not only satisfies the invariance to translation, scale and rotation, but also improves accuracy and efficiency of shoeprints matching on the scene.A large number of experiences were carried out and experimental results were analyzed, edge detection based on canny operator can not only to eliminate noise, but also preserves the edges and details of images effectively.更多还原