说明：  基于内容的图象检索系统代码图片预处理是为了使图片归一化，归一化的目的是将每幅原始图像调整到相同的尺寸和对应位置，从而消除平移、缩放和旋转对于图像鉴别的影响以方便对图片进行的特征提取。
(Content-Based Image Retrieval System code image preprocessing is to enable the picture normalized, normalized objective is to adjust each piece of the original image to the same size and the corresponding location, thereby eliminating the translation, scaling and rotation for the image identification impact on the picture to facilitate feature extraction.)