Sample Codes: rotate & scale an image with OpenCV on Ubuntu 16.04

First of all, please configure opencv on your linux system.


simple build from source code:
git clone https://github.com/lengerrong/opencv.git
cd opencv/
mkdir build
cd build/
cmake ..
make -j128
sudo make install
sudo ldconfig

Sample codes:
#include <opencv2/opencv.hpp>

#include <errno.h>
#include <iostream>
#include <limits.h>
#include <stdlib.h>

using namespace std;
using namespace cv;

void rotateimage(const Mat& image, Mat& out)
{
    // rotation angle in degrees. Positive values mean counter-clockwise rotation
    cout << "please enter rotate degree:" << endl;   
    double angle;
    cin >> angle;
    // isotropic scale factor.
    cout << "please enter scale factor:" << endl;
    double scale;   
    cin >> scale;
    //rotate centre
    Point2f center = Point2f(image.cols / 2, image.rows / 2);
    // calculates an affine matrix of 2D rotation
    Mat rotateMat = getRotationMatrix2D(center, angle, scale);
    // applies an affine transformation to an image
    warpAffine(image, out, rotateMat, image.size());
}

int main(int argc, char **argv)
{
    if (argc < 2) {
        cout << "no input image" << endl;
        return -1;
    }
    // resolve image path
    char resolvepath[PATH_MAX];
    if (!realpath(argv[1], resolvepath)) {
        cout << strerror(errno) << endl;
        return -2;
    }
    cout << "rotate image :" << resolvepath << endl;
    Mat image = imread(resolvepath);
    if (image.empty()) {
        cout << "read image failed";
        return -3;
    }
    Mat out;
    rotateimage(image, out);
    imwrite("rotate.png", out);
    return 0;
}

Compile command:
g++ -o rotateimage rotateimage.cpp  `pkg-config --cflags --libs opencv`

Run rotateimage:
./rotateimage  origin.png
rotate image :/home/lenger/origin.png
please enter rotate degree:
-17.8
please enter scale factor:
0.5

Sample Result:
origin.png

rotate.png