OpenCV4教程——3.3 绘制直线

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本文将指导你如何在OpenCV中使用line()函数绘制直线。通过详细解析函数参数，包括点坐标、颜色、厚度等，以及提供C++和Python的代码示例，帮助读者掌握基本的图像处理技能。

目标

我们将学习在 OpenCV 中进行绘制操作，我们的目标包括：

绘制直线。使用 line() 函数。

绘制直线

Draws a line segment connecting two points.

头文件

#include <opencv2/imgproc.hpp>

原型

C++/Java
void cv::line(InputOutputArray img,
              Point 	       pt1,
              Point 	       pt2,
              const Scalar &   color,
              int              thickness = 1,
              int              lineType = LINE_8,
              int              shift = 0)
Python:
img	= cv.line(	img, pt1, pt2, color[, thickness[, lineType[, shift]]]	)

输入参数

img	Image.
pt1	First point of the line segment.
pt2	Second point of the line segment.
color	Line color.
thickness	Line thickness.
lineType	Type of the line. See LineTypes.
shift	Number of fractional bits in the point coordinates.

例子

#include <opencv2/core.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/highgui.hpp>

#define w 400

using namespace cv;

void MyLine(Mat img, Point start, Point end);

int main( void ){
    char atom_window[] = "Drawing 1: Atom";
    char rook_window[] = "Drawing 2: Rook";

    Mat rook_image = Mat::zeros( w, w, CV_8UC3 );
    MyLine( rook_image, Point( 0, 15*w/16 ), Point( w, 15*w/16 ) );
    MyLine( rook_image, Point( w/4, 7*w/8 ), Point( w/4, w ) );
    MyLine( rook_image, Point( w/2, 7*w/8 ), Point( w/2, w ) );
    MyLine( rook_image, Point( 3*w/4, 7*w/8 ), Point( 3*w/4, w ) );

    imshow( atom_window, atom_image );

    waitKey( 0 );

    return 0;
}

void MyLine( Mat img, Point start, Point end ) {
  int thickness = 2;
  int lineType = LINE_8;
  line( img,
    start,
    end,
    Scalar( 0, 0, 0 ),
    thickness,
    lineType );
}