opencv extracting all horizontal and vertical lines separately using morphological operation

Question

I am new to opencv. I am working with opencv and C++ on visual studio 2013. I have a task to extract all horizontal and vertical lines of a document containing a table separately and use that to extract the cells present in the table.

I can only use morphological operation to achieve that.

Can anyone suggest the procedure to achieve that?

Here is a sample document.

Sample Image

Are you allowed to use Hough? docs.opencv.org/doc/tutorials/imgproc/imgtrans/hough_lines/… — Antonio
– Antonio, Commented Jan 22, 2015 at 12:51
any document image, for sample you can look at this URL w3.org/TR/html401/images/table2.gif — MOHIT.A Jain
– MOHIT.A Jain, Commented Jan 22, 2015 at 13:05

MOHIT.A Jain · Accepted Answer · 2015-01-27 10:03:39Z

2

enter image description here Finally got the output. Look at the code.

string src = "d://sabari//23.jpg";
Mat im = imread(src);
Mat gray;


if (im.channels() == 3)
{
    cvtColor(im, gray, CV_BGR2GRAY);
}
else
{
    gray = im;
}

adaptiveThreshold(~gray, gray, 255, CV_ADAPTIVE_THRESH_MEAN_C, THRESH_BINARY, 15, -2);
Mat vertical = gray.clone();
int horizontalsize = gray.cols / 30;

Mat structure = getStructuringElement(MORPH_RECT, Size(horizontalsize,1));

erode(gray, gray,structure, Point(-1, -1));
dilate(gray, gray,structure, Point(-1, -1));

imshow("ans", gray);
imwrite("d://out2.jpg", gray);

int verticalsize = vertical.rows / 30;

Mat verticalStructure = getStructuringElement(MORPH_RECT, Size( 1,verticalsize));

erode(vertical, vertical, verticalStructure, Point(-1, -1));
dilate(vertical, vertical, verticalStructure, Point(-1, -1));

imshow("ans1", vertical);
imwrite("d://out3.jpg", vertical);

edited Jan 27, 2015 at 10:03

answered Jan 23, 2015 at 6:57

MOHIT.A Jain

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2 Comments

MOHIT.A Jain Over a year ago

I got horizontal line separately and vertical lines separately. As i used line as my structuring element, it is able to delete rest elements and i am left with only lines. When i need vertical lines i use structure element "verticalStructure" as mentioned in the code.

Antonio Over a year ago

Well done, if you show an output image it will be even more helpful to people reading this post in the future.

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