Björn Larsson's profile - activity

A rotated rectangle consists of four points, the corners. Therefore it should be possible to convert it to a contour. Th

Keep in mind that indicator == 0 when the point is on the rectangle edge.

A rotated rectangle consists of four points, the corners. Therefore it should be possible to convert it to a contour. Th

Goal: Adding a solid white line to a black'n'white image.

I'm trying to extract text from an image by cropping it and then adding a solid border with copyMakeBorder(). My problem is that I can't make the border solid. It seems like the copyMakeBorder() uses information from my initial image instead.

This is my code:

void OcvCardReader::cropToAreaWithSolidBorder(Mat image, const Rect2f area) {
    //Crop the image.
    image = image(area);
    //Add the border.
    int borderSize = 10;
    copyMakeBorder(image, image,
        borderSize, borderSize, borderSize, borderSize,
        BORDER_CONSTANT, Scalar(255));
}

My input image looks like this:

This is after the crop:

And finally, after adding the border:

Note the black pixels att the bottom left. I had expected a border to be white all around. I also tried to use Scalar(0) to see if it makes any difference. It doesn't.

Curiously, it works well if I convert the image to a 3-channel Mat and then use Scalar(255, 255, 255), but that seems like a detour to me.

So, why does copyMakeBorder() return a border that isn't solid?

So, I've tried a few different solutions based on the comments I got. First I tried to change the call to call by refer

So, I've tried a few different solutions based on the comments I got. First I tried to change the call to call by refer

copyMakeBorder returns un-solid border Goal: Adding a solid white line to a black'n'white image. I'm trying to extract

Oh! I thought a Mat was big enough to be passed by reference automagically. Thanks! I will try that! :-D

copyMakeBorder returns un-solid border Goal: Adding a solid white line to a black'n'white image. I'm trying to extract

Thanks, that solved my problem! :-)

Thanks, that solved my problem!

Thanks, that solved my problem! Unfortunately, I can't up-vote your answer due to low karma, even though you deserve it.

I have a case with several contours

std::vector<std::vector<cv::Point>> contours;

I want to get the smallest area rectangle RotatedRect containing all these contours. I have tried minAreaRect() but it returns an exception (probably because I pass it more than one contour).

What would be the best way of getting the minimal area rectangle when you're dealing with more than one contour?

Minimal area rectangle for multiple contours I have a case with several contours std::vector<std::vector<cv::Poin

A rotated rectangle, but bonus points if the answer includes bounding box as well! :-)

Minimal area rectangle for multiple contours I have a case with several contours std::vector<std::vector<cv::Poin

A rotated rectangle.

A rotated rectangle.

Minimal area rectangle for multiple contours I have a case with several contours std::vector<std::vector<cv::Poin