Template matching usink mask in opencv (emgu)

Question

I would like to find a piece of an image inside another image. However, I have some regions pixels in both images that I don't want to take into account. So I was thinking of using some type of mask with zeros or ones to indicate the good pixels.

I am using the MatchTemplate method from emgu and it does not accept a mask. Is there any other way of doing what I would like to do? Thank you!

ReferenceImage.MatchTemplate(templateImage, Emgu.CV.CvEnum.TM_TYPE.CV_TM_CCORR_NORMED);

Can you provide the image and the Template to help us understand? Also, please tell use what part of the image you want to mask. — Jean-François Côté, Oct 03 '13 at 13:20
I just found another question about exactly the same issue: http://stackoverflow.com/questions/4761940/opencv-template-matching-and-transparency — Jorge Otero-Millan, Oct 08 '13 at 00:16

score 0 · Answer 1 · answered Oct 08 '13 at 03:03

I thought of a solution. Asuming that referenceImageMask and templateMask have 1s in the good pixels and 0s in the bad ones. And that referenceImage and templateImage have already been masked and have 0s in the bad pixels as well.

Then, the first result of template matching will give the not normalized cross correlation between the images.

The second template matching will give for each possible offset the number of pixels that were at the same time different from zero (unmasked) in both images.

Then, normalizing the correlation by that number should give the value I wanted. The average product for the pixels that are not masked in both images.

Image<Gray, float> imCorr = referenceImage.MatchTemplate(templateImage,      Emgu.CV.CvEnum.TM_TYPE.CV_TM_CCORR);
Image<Gray, float> imCorrMask = referenceImageMask.MatchTemplate(templateMask, Emgu.CV.CvEnum.TM_TYPE.CV_TM_CCORR);
imCorr = imCorr .Mul(imCorrMask .Pow(-1));

score 0 · Answer 2 · answered Jun 29 '21 at 07:33

0

Today you could use this method:

CvInvoke.MatchTemplate(actualImage, expectedImage, result, TemplateMatchingType.CcoeffNormed, mask);

answered Jun 29 '21 at 07:33

Andrey Gurenkov

58
7

Hi Andrey, can you elaborate a bit on why this would work? A little context goes a long way for others reading the post - When was it added, stuff like that :) – Johan Aspeling Jun 29 '21 at 12:09
1

Just look for documentation here: https://www.emgu.com/wiki/files/4.5.2/document/html/ee43f981-70ee-04c2-4c10-764da38f0781.htm – Andrey Gurenkov Aug 03 '21 at 20:17

Template matching usink mask in opencv (emgu)

2 Answers2