无法检测图像的水平线 [英] Cannot detect horizontal lines of an image

问题描述

我正在编写一个移动应用程序来绘制统计数据表图像的图形表示（图形和图表）。目前我正在使用OpenCV和c ++编写项目的表检测模块。

我已经应用了adaptiveThreshold和Canny来检测最大的Contour并裁剪掉了表格。 （，此处应使用RETR_EXTERNAL。

然后

• 使用RETR_EXTERNAL选项再次查找轮廓。使用CV_FILLED选项查看绘制的轮廓。

• 计算 绑定Rect 或 旋转矩形 以供进一步使用。

参见bounding rect。

参见旋转的矩形。

I'm writing a mobile app to plot the graphical representation (graphs and charts) of images of statistical data tables. currently i'm writing the table detection module of the project using OpenCV with c++.

I have already applied adaptiveThreshold and Canny to detect the largest Contour and cropped out the table. (https://i.imgur.com/clBS3dr.jpg)

and following is the code i'm using to detect the horizontal and vertical lines: Note: "Crop" is the already cropped table image(Mat)

cvtColor(crop, crop, CV_RGB2GRAY);
adaptiveThreshold(crop, crop, 255, CV_ADAPTIVE_THRESH_MEAN_C,CV_THRESH_BINARY, 31, 15); 
    Mat dst1, cdst1;
Canny(crop, dst1, 50, 200, 3); 
cvtColor(dst1, cdst1, CV_GRAY2BGR); 

vector<Vec2f> lines;
// detect lines
HoughLines(dst1, lines, 1, CV_PI/180, 200, 0, 0 );
//HoughLinesP(dst1, lines, 1, CV_PI/180, 150, 0, 0);

// draw lines
for( size_t i = 0; i < lines.size(); i++ )
{
    float rho = lines[i][0], theta = lines[i][1];
    //if( theta>CV_PI/180*170 || theta<CV_PI/180*10){
        Point pt1, pt2;
        double a = cos(theta), b = sin(theta);
        double x0 = a*rho, y0 = b*rho;
        pt1.x = cvRound(x0 + 1000*(-b));
        pt1.y = cvRound(y0 + 1000*(a));
        pt2.x = cvRound(x0 - 1000*(-b));
        pt2.y = cvRound(y0 - 1000*(a));
        line( cdst1, pt1, pt2, Scalar(0,0,255), 3, CV_AA);
    //}
}
namedWindow("detected lines",WINDOW_NORMAL);
imshow("detected lines", cdst1);

And the result of this code comes out like this : https://i.imgur.com/yDuCqmo.jpg

What am I going wrong to the Horizontal lines only to reach half of the image?

解决方案

if you are trying to extract each cell in the table you can try contour processing,

• Do binary invert threshold in the source.

• Find contour, here you should use RETR_EXTERNAL.

• Then draw contour with CV_FILLED, here you will get mask for your table. Notice that here you should get only one contour, and assumes there wont be any noise outside the table. Or if you got multiple contour draw largest as mask.

• Bitwise xor between threshold and mask

• Again Find contour, with RETR_EXTERNAL option. See the drawn contour with CV_FILLED option.

• Calculate bounding Rect or Rotated rect for contour for further use.

See bounding rect.

See rotated rect.

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