Rotate 90 degree because iOS flips image as it takes photo

void rot90(cv::Mat &matImage, int rotflag)
{ //1=CW, 2=CCW, 3=180 
    if (rotflag == 1)
    {transpose(matImage, matImage); flip(matImage, matImage,1); //transpose+flip(1)=CW } 
    else if (rotflag == 2) 
    { transpose(matImage, matImage); flip(matImage, matImage,0); //transpose+flip(0)=CCW } 
    else if (rotflag ==3) { flip(matImage, matImage,-1); //flip(-1)=180 } 
    else if (rotflag != 0){ //if not 0,1,2,3: 
    cout << "Unknown rotation flag(" << rotflag << ")" << endl; } 
}