opencv 旋转图像函数实现 等同于matlab里的rotate（） （注：旋转后图像变大，超出部分填为黑色）

注：clockwise=true 顺时针旋转

clockwise=false 逆时针旋转

IplImage* rotateImage(IplImage* src, int angle, bool clockwise)

{
angle = abs(angle) % 180;
if (angle > 90)
{
angle = 90 - (angle % 90);
}
IplImage* dst = NULL;
int width =
(double)(src->height * sin(angle * CV_PI / 180.0)) +
(double)(src->width * cos(angle * CV_PI / 180.0 )) + 1;
int height =
(double)(src->height * cos(angle * CV_PI / 180.0)) +
(double)(src->width * sin(angle * CV_PI / 180.0 )) + 1;
int tempLength = sqrt((double)src->width * src->width + src->height * src->height) + 10;
int tempX = (tempLength + 1) / 2 - src->width / 2;
int tempY = (tempLength + 1) / 2 - src->height / 2;
int flag = -1;

dst = cvCreateImage(cvSize(width, height), src->depth, src->nChannels);
cvZero(dst);
IplImage* temp = cvCreateImage(cvSize(tempLength, tempLength), src->depth, src->nChannels);
cvZero(temp);

cvSetImageROI(temp, cvRect(tempX, tempY, src->width, src->height));
cvCopy(src, temp, NULL);
cvResetImageROI(temp);

if (clockwise)
flag = 1;

float m[6];
int w = temp->width;
int h = temp->height;
m[0] = (float) cos(flag * angle * CV_PI / 180.);
m[1] = (float) sin(flag * angle * CV_PI / 180.);
m[3] = -m[1];
m[4] = m[0];
// 将旋转中心移至图像中间
m[2] = w * 0.5f;
m[5] = h * 0.5f;
//
CvMat M = cvMat(2, 3, CV_32F, m);
cvGetQuadrangleSubPix(temp, dst, &M);
cvReleaseImage(&temp);
return dst;
}