检测图像。你需要学习一点关于图像处理来解决这个问题。建议您阅读模板匹配或更多关于对象识别。特别是对于汽车检测，如果你知道他们将被看到在某一角度（例如头），我会尝试 Viola-Jones检测，其在 OpenCV 中实现为基于haar的功能级联检测 。虽然OpenCV不是一个matlab库，你可以找到一些在matlab的图像处理工具箱，做一个类似的工作（或接口到OpenCV）

There's a whole world of methods for object detection in images. You need to learn a little bit about image processing to solve this problem. I suggest you read about template matching or more generally about Object recognition. Specifically for car detection, if you know they will be seen at a certain angle (head on, for example) i'd try Viola-Jones detection which is implemented in OpenCV as haar-based feature cascade detection. Although OpenCV is not a matlab library, you can probably find something in matlab's image processing toolboxes that does a similar job (or interface into OpenCV)