//旋转图像内容不变,尺寸相应变大
IplImage* rotateImage2(IplImage* img, int degree)
{
double angle = degree * CV_PI / 180.;
double a = sin(angle), b = cos(angle);
int width=img->width, height=img->height;
//旋转后的新图尺寸
int width_rotate= int(height * fabs(a) + width * fabs(b));
int height_rotate=int(width * fabs(a) + height * fabs(b));
IplImage* img_rotate = cvCreateImage(cvSize(width_rotate, height_rotate), img->depth, img->nChannels);
cvZero(img_rotate);
//保证原图可以任意角度旋转的最小尺寸
int tempLength = sqrt((double)width * width + (double)height *height) + 10;
int tempX = (tempLength + 1) / 2 - width / 2;
int tempY = (tempLength + 1) / 2 - height / 2;
IplImage* temp = cvCreateImage(cvSize(tempLength, tempLength), img->depth, img->nChannels);
cvZero(temp);
//将原图复制到临时图像tmp中心
cvSetImageROI(temp, cvRect(tempX, tempY, width, height));
cvCopy(img, temp, NULL);
cvResetImageROI(temp);
//旋转数组map
// [ m0 m1 m2 ] ===> [ A11 A12 b1 ]
// [ m3 m4 m5 ] ===> [ A21 A22 b2 ]
float m[6];
int w = temp->width;
int h = temp->height;
m[0] = b;
m[1] = a;
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, img_rotate, &M);
cvReleaseImage(&temp);
return img_rotate;
}
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