How to change the size of an image and add a border in OpenCV using C++?

In this topic, we will see another application of trackbar. Here, we will use track-bar to change the size of an image and add a border to the image and change the border's size using the track-bar.

Using the following program, we can change the size of an image, add a border, change the border's size and rotate the image. It is similar to the previous example.

The following program demonstrates how to add multiple sliders in the same track-bar.

Example

#include<iostream> #include<opencv2/highgui/highgui.hpp> #include<opencv2/imgproc/imgproc.hpp> using namespace std; using namespace cv;    int Rotate = 180;//initializing angle//    int Scale = 50;//initializing scale//    int Border = 0;//initial Border//    Mat before_Rotate;//declaring matrix for before rotation//    int vertical = 0;//initial vertical value//    int horizontal = 0;//initial horizontal value//    void rotator(int, void*){ //function to rotate image//    Mat Rotation = getRotationMatrix2D(Point(horizontal, vertical),(Rotate - 180), Scale / 50.0);//affine transformation matrix for 2D rotation//    Mat Rotated;//matrix for rotated image    warpAffine(before_Rotate, Rotated, Rotation, before_Rotate.size(), INTER_LINEAR, Border, Scalar());//applying affine transformation//    imshow("RotatedImage", Rotated);//show rotated image// } int main(int argc,char**argv) {    before_Rotate = imread("sky.jpg");//loading image in the matrix//    vertical = before_Rotate.rows / 2;//getting midpoint of vertical pixels//    horizontal = before_Rotate.cols / 2;//getting midpoints of horizontal pixels//    namedWindow("BeforeRotate");//declaring window to show image before rotation//    imshow("BeforeRotate", before_Rotate);//showing image before rotation//    namedWindow("AfterRotate");//declaring window to show image after rotation//          createTrackbar("Angle", "AfterRotate", &Rotate, 360, rotator);//creating trackbar for rotation//    createTrackbar("Scale", "AfterRotate", &Scale, 100, rotator);//creating trackbar to change size//    createTrackbar("Border Mode", "After Rotate", &Border, 5, rotator);//creating trackbar to add border//    int cbfunction = 0;//initiate value of rotator function's argument//    rotator(cbfunction, &cbfunction);//call back rotator function//    waitKey(0);//wait till keystroke//    return 0; }

Output