一个空间点P绕一个中心点C旋转可用接续的三个变换来实现：第1个变换平移点C到坐标系原点位置，第2个变换将点P绕原点旋转，第3个变换平移点C回到其相对于坐标系原点的原始位置。当原始图像点乘以变换矩阵，得到新的图像位置点时，其位置可能不是整数值，该位置的灰度值需要通过灰度插值获得。在不改变输出图像大小的情况下，超出原始图片范围的区域，MATLAB原有函数imrotate的处理方法为将其灰度值全部置零，本文通过取模操作对超出区域进行了另外一种控制方法imrotate_my函数，能够较好的显示出图像旋转的边界变化。

-A space around the center point P C available in three rotating to realize the transformation: the first one translation: C to coordinate transformation, the origin place of 2 transform point P around the rotation, the origin of the three points to the transformation of C translation relative to the original position of axis. When the original image point multiply the transformation matrix, a new image position, the position may not integer, this position gray value by gray interpolation gain needed. No change in the size of the image output circumstance, the area beyond the original image, the original function imrotate MATLAB treatment method for the grey value all zeros, based on beyond the area take mould operation on another control method imrotate_my function, to better show of image rotation boundaries.