matlab下的手指静脉图像预处理：均衡化，膨胀，腐蚀，细化，手指边缘检测，截取roi区域，尺度归一化以及灰度归一化。(Finger vein image preprocessing under matlab: equalization, expansion, corrosion, thinning, finger edge detection, interception of ROI region, scale normalization and gray normalization.)