圖像旋轉的實現

本文轉載地址：http://blog.csdn.net/carson2005/article/details/36900401

上一篇轉載的文章（http://blog.csdn.net/carson2005/article/details/36900161）介紹了圖像旋轉的原理，這裏給出代碼實現，具體原理請參考上面的鏈接；

實現代碼：

void ImgRotate(cv::Mat imgIn, float theta, cv::Mat& imgOut)
{
    int oldWidth = imgIn.cols;
    int oldHeight = imgIn.rows;

    // 源圖四個角的座標（以圖像中心爲座標系原點）
    float fSrcX1,fSrcY1,fSrcX2,fSrcY2,fSrcX3,fSrcY3,fSrcX4,fSrcY4;
    fSrcX1 = (float) (- (oldWidth  - 1) / 2);
    fSrcY1 = (float) (  (oldHeight - 1) / 2);
    fSrcX2 = (float) (  (oldWidth  - 1) / 2);
    fSrcY2 = (float) (  (oldHeight - 1) / 2);
    fSrcX3 = (float) (- (oldWidth  - 1) / 2);
    fSrcY3 = (float) (- (oldHeight - 1) / 2);
    fSrcX4 = (float) (  (oldWidth  - 1) / 2);
    fSrcY4 = (float) (- (oldHeight - 1) / 2);

    // 旋轉後四個角的座標（以圖像中心爲座標系原點）
    float fDstX1,fDstY1,fDstX2,fDstY2,fDstX3,fDstY3,fDstX4,fDstY4;
    fDstX1 =  cos(theta) * fSrcX1 + sin(theta) * fSrcY1;
    fDstY1 = -sin(theta) * fSrcX1 + cos(theta) * fSrcY1;
    fDstX2 =  cos(theta) * fSrcX2 + sin(theta) * fSrcY2;
    fDstY2 = -sin(theta) * fSrcX2 + cos(theta) * fSrcY2;
    fDstX3 =  cos(theta) * fSrcX3 + sin(theta) * fSrcY3;
    fDstY3 = -sin(theta) * fSrcX3 + cos(theta) * fSrcY3;
    fDstX4 =  cos(theta) * fSrcX4 + sin(theta) * fSrcY4;
    fDstY4 = -sin(theta) * fSrcX4 + cos(theta) * fSrcY4;

    int newWidth  = ( max( fabs(fDstX4 - fDstX1), fabs(fDstX3 - fDstX2) ) + 0.5);
    int newHeight = ( max( fabs(fDstY4 - fDstY1), fabs(fDstY3 - fDstY2) )  + 0.5);

    imgOut.create(newHeight, newWidth, imgIn.type());

    float dx = -0.5*newWidth*cos(theta) - 0.5*newHeight*sin(theta) + 0.5*oldWidth;
    float dy = 0.5*newWidth*sin(theta) - 0.5*newHeight*cos(theta) + 0.5*oldHeight;

    int x,y;
    for (int i=0; i<newHeight; i++)
    {
        for (int j=0; j<newWidth; j++)
        {
            x = float(j)*cos(theta) + float(i)*sin(theta) + dx;
            y = float(-j)*sin(theta) + float(i)*cos(theta) + dy;

            if ((x<0) || (x>=oldWidth) || (y<0) || (y>=oldHeight))
            {
                if (imgIn.channels() == 3)
                {
                    imgOut.at<cv::Vec3b>(i,j) = cv::Vec3b(0,0,0);
                }
                else if (imgIn.channels() == 1)
                {
                    imgOut.at<uchar>(i,j) = 0;
                }
            }
            else
            {
                if (imgIn.channels() == 3)
                {
                    imgOut.at<cv::Vec3b>(i,j) = imgIn.at<cv::Vec3b>(y,x);
                }
                else if (imgIn.channels() == 1)
                {
                    imgOut.at<uchar>(i,j) = imgIn.at<uchar>(y,x);
                }
            }
        }
    }
}

測試代碼：

void ImgRotateTest()
{
    cv::Mat srcImg = cv::imread("test.jpg");
    if (srcImg.empty())
    {
        printf("srcImg load error \n");
        system("pause");
        exit(-1);
    }

    float angle = 30.0f*3.1415926/180.0f;

    cv::Mat dstImg;
    ImgRotate(srcImg, angle, dstImg);
    cv::imwrite("result.jpg", dstImg);
    cv::imshow("src", srcImg);
    cv::imshow("dst", dstImg);
    cv::waitKey(0);

}