MareArts Computer Vision Study.

refer to code.

sample point is 100,100

firstly, I rotated image as 90 degree and point.

And compare origin image & pt where rotated point is placed in right position.

import numpy as np
import cv2
from matplotlib import pyplot as plt

def rotate_image(angle, width, height):
    image_center = (width/2, height/2)
    rotation_mat = cv2.getRotationMatrix2D(image_center, angle, 1.)
    abs_cos = abs(rotation_mat[0,0]) 
    abs_sin = abs(rotation_mat[0,1])
    bound_w = int(height * abs_sin + width * abs_cos)
    bound_h = int(height * abs_cos + width * abs_sin)
    rotation_mat[0, 2] += bound_w/2 - image_center[0]
    rotation_mat[1, 2] += bound_h/2 - image_center[1]
    return rotation_mat, (bound_w, bound_h)

#open image
image = cv2.imread('img.png')
sample_pt =(100,100)

#get rotate mat, bound
height, width = image.shape[:2]
rotation_mat, (bound_w, bound_h) = rotate_image(90, width, height)

#rotate image
image_90 = cv2.warpAffine(image, rotation_mat, (bound_w, bound_h))
#rotate pt
sample = np.array([100, 100, 1])
sample_90 = np.matmul(rotation_mat, sample)


#origin image & pt
cv2.circle(image, sample_pt, 1, (0, 0, 255), 2, cv2.LINE_AA)

#rotated image & pt
cv2.circle(image_90, (int(sample_90[0]), int(sample_90[1])), 1, (0, 0, 255), 2, cv2.LINE_AA)


image = image[:,:,::-1]
plt.figure(figsize=(10, 10), dpi=100)
plt.imshow(image)

image_90 = image_90[:,:,::-1]
plt.figure(figsize=(10, 10), dpi=100)
plt.imshow(image_90)

origin image with point

90 rotated image and point

Thank you.

www.marearts.com

line, circle, rectangle, ellipse, polyline, fillConvexPoly, putText, drawContours example source code!!.

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//http://study.marearts.com/2016/06/opencv-mat-copyto-clone-roi-example-code.html

#include "opencv2/opencv.hpp"
#include "opencv2/highgui.hpp"
#include <iostream>
#include <vector>

#ifdef _DEBUG               
#pragma comment(lib, "opencv_core331d.lib")       
#pragma comment(lib, "opencv_highgui331d.lib")    
#pragma comment(lib, "opencv_imgcodecs331d.lib")  
#pragma comment(lib, "opencv_objdetect331d.lib")  
#pragma comment(lib, "opencv_imgproc331d.lib")  
#pragma comment(lib, "opencv_videoio331d.lib")    
#else       
#pragma comment(lib, "opencv_core331.lib")       
#pragma comment(lib, "opencv_highgui331.lib")    
#pragma comment(lib, "opencv_imgcodecs331.lib")    
#pragma comment(lib, "opencv_objdetect331.lib")  
#pragma comment(lib, "opencv_imgproc331.lib")  
#pragma comment(lib, "opencv_videoio331.lib")    
#endif        


using namespace std;
using namespace cv;

int main()
{
    Mat img(500, 500, CV_8UC3);
    img.setTo(255);

    
    ///////////////////////////////////////////////////
    //line example
    cv::Point pt(300, 300);
    line(img, Point(10, 10), pt, CV_RGB(255, 0, 0), 2);
    line(img, Point(300, 10), Point(30, 300), Scalar(255, 0, 0), 2);
    ///////////////////////////////////////////////////


    ///////////////////////////////////////////////////
    //Circle example
    circle(img, Point(250, 250), 100, CV_RGB(0, 255, 0), 3);
    cv::Point center(400, 400);
    circle(img, center, 300, Scalar(255, 255, 0), 10);
    circle(img, Point(40, 40), 10, Scalar(255, 0, 0), -1);
    ///////////////////////////////////////////////////


    ///////////////////////////////////////////////////
    //rectangle example
    rectangle(img, Rect(10, 10, 200, 200), CV_RGB(255, 0, 0), 2);
    rectangle(img, Rect(Point(40, 40), Point(400, 400)), Scalar(255, 0, 0), 10);
    ///////////////////////////////////////////////////


    /////////////////////////////////////////////////// 
    //ellipse example 1
    ellipse(img, Point(100, 100), Size(100, 50), 0, 0, 360, CV_RGB(255, 0, 0));
    ellipse(img, Point(100, 100), Size(100, 50), 30, 0, 360, CV_RGB(0, 255, 0));
    ellipse(img, Point(100, 100), Size(100, 50), 60, 0, 360, CV_RGB(0, 0, 255));

    ellipse(img, Point(300, 300), Size(100, 50), 0, 0, 180, CV_RGB(255, 0, 0));
    ellipse(img, Point(300, 300), Size(100, 50), 30, 0, 270, CV_RGB(0, 255, 0));
    ellipse(img, Point(300, 300), Size(100, 50), 60, 0, 360, CV_RGB(0, 0, 255));
    ///////////////////////////////////////////////////

    /////////////////////////////////////////////////// 
    //ellipse example 2
    RotatedRect rRect = RotatedRect(Point2f(300, 300), Size2f(300, 100), 30);
    ellipse(img, rRect, CV_RGB(255, 0, 0));

    //draw rect and inside rect in RotatedRect
    Point2f vertices[4];
    rRect.points(vertices);
    for (int i = 0; i < 4; i++)
        line(img, vertices[i], vertices[(i + 1) % 4], Scalar(0, 255, 0));

    Rect brect = rRect.boundingRect();
    rectangle(img, brect, Scalar(255, 0, 0));
    ///////////////////////////////////////////////////
    

    /*
    ///////////////////////////////////////////////////
    //polylines example 1 
    vector< Point> contour;
    contour.push_back(Point(50, 50));
    contour.push_back(Point(300, 50));
    contour.push_back(Point(350, 200));
    contour.push_back(Point(300, 150));
    contour.push_back(Point(150, 350));
    contour.push_back(Point(100, 100));

    const Point *pts = (const cv::Point*) Mat(contour).data;
    int npts = Mat(contour).rows;

    std::cout << "Number of polygon vertices: " << npts << std::endl;
    // draw the polygon 
    polylines(img, &pts, &npts, 1, false, Scalar(0, 255, 0));

    //polylines example 2 
    contour.clear();
    contour.push_back(Point(400, 400));
    contour.push_back(Point(250, 250));
    contour.push_back(Point(50, 300));

    pts = (const cv::Point*) Mat(contour).data;
    npts = Mat(contour).rows;
    polylines(img, &pts, &npts, 1, true, Scalar(255, 0, 0));
    ///////////////////////////////////////////////////
    */


    /*
    ///////////////////////////////////////////////////
    //fillConvexPoly example 1 
    cv::Point ptss[4];
    ptss[0] = cv::Point(100, 100);
    ptss[1] = cv::Point(150, 200);
    ptss[2] = cv::Point(300, 300);
    ptss[3] = cv::Point(400, 100);

    cv::fillConvexPoly(img, ptss, 4, cv::Scalar(0, 0, 200));
    ///////////////////////////////////////////////////
    */

    /*
    ///////////////////////////////////////////////////
    //textout example 1
    char TestStr[100];
    sprintf_s(TestStr, "total time : %lf sec", 0.001);
    putText(img, TestStr, Point(10, 250), CV_FONT_NORMAL, 1, Scalar(0, 0, 0), 1, 1); //OutImg is Mat class;
    ///////////////////////////////////////////////////
    */

    
    imshow("show0", img);
    waitKey(0);

    return 0;
}

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MareArts Computer Vision Study.

opencv, cv2, rotate image & point

OpenCV Drawing Example, (line, circle, rectangle, ellipse, polyline, fillConvexPoly, putText, drawContours)