Resampling grid to remove noise before extracting chain code

edit

Thanks a lot for your advice. I will try to implement it. I did not understand how to "threshold to remove grid cells that only barely had anything in them". How to do it, do you have any idea?

I have tried implementing it. I am not getting the required result.

You're operating on a binary image, right? You after you downsample and then upsample again you need to run the threshold function to return it to a binary state.

Also, how far are you downsampling? The image you show looks to be about 5x5 to 1, so you should be using a scale factor of 0.2

I have used the following code:

int main() { Mat img = imread("resampling.png", 0);

Size imgSize = img.size();

Size downSize = Size(img.size().width / 2, img.size().height / 2);
Canny(img, img, 100, 100 * 2, 3, false);


imshow("Original", img);
resize(img, img,downSize, 0, 0, INTER_AREA);

imshow("down", img);
resize(img, img, imgSize, 0, 0, INTER_NEAREST);

imshow("beforeThreshold", img);
threshold(img, img,130, 130 * 3, THRESH_BINARY);

imshow("Original1", img);

waitKey(0);

}

I have uploaded a picture of what I have tried above.

Oh wow, ok, I did mis-understand what you're doing.

So typically you would downsample before you do the canny edge detection. But your image is already squared off. So it won't do much of anything. Your chain code should already be evened out, only 30 or 31 points. What this method is supposed to do is reduce the number of points because of things like curves and whatnot.

So you can downsample far enough to lose features, but it will be very far. It would have to be smaller than 9x10 pixels.

Do u know how to extract chain code from a shape so that it is scale invariant?

No idea, but I found this: http://www.cis.hut.fi/research/IA/pap...

Thanks for helping me..