Feature Matching with FLANN Tutorial

asked 2013-04-12 09:08:23 -0600

Immi
81 ●2 ●8

updated 2013-04-15 01:57:00 -0600

Hello all!

I've tried this tut: http://docs.opencv.org/doc/tutorials/features2d/feature_flann_matcher/feature_flann_matcher.html#feature-flann-matcher .

When I'm adding: equalizeHist(img_1,img_1) after loading the images, the program will crash. This crash at "matcher.match( descriptors_1, descriptors_2, matches );" with error: "OpenCV Error: Unsupported format or combination of formats (type=0) in unknown function, file ......\src\opencv\modules\flann\src\miniflann.cpp, line 315"

What changes in format does equalizeHist() do? Do you have some hints for me, to evade this error? Thanks in advance. Wish you a nice weekend.

Solution: http://answers.opencv.org/question/11449/flann-algorithm-cannot-find-any-descriptor/ I was using the same image. Immi

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Have you made any other changes to the code? I tried running the tutorial code with and without equalizeHist(), and even emptied the descriptors and keypoints after running their respective functions and it still worked fine on my machine.

HD_Mouse ( 2013-04-12 13:16:15 -0600 )edit

Hi, I've just changed imread from variable to path and deleted the lines with check of arguments.Thanks for your help.

Immi ( 2013-04-15 01:14:19 -0600 )edit

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answered 2013-04-12 10:12:46 -0600

Guanta
6736 ●6 ●25 ●79

updated 2013-04-12 10:13:17 -0600

According to the docu, equalizeHist doesn't change the image-format, however, the docu doesn't state if it works in-place or not, so please try it this way:

cv::Mat tmp;
equalizeHist(img_1, tmp);
img_1 = tmp;

Also note, that your image must be in grayscale - is that the case?

If this doesn't help, one other idea comes to my mind: Have you checked if you get keypoints from your equalized image at all? If not, descriptors_1 will be empty and you'll probably get such an error.

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equalizeHist does allow you to read and write from and to the same source. I am doing it in all my projects. I am guessing his images are BGR, and not yet converted to grayscale.

StevenPuttemans ( 2013-04-12 16:28:07 -0600 )edit

Hi, thanks for your answers. I've loaded images with img_1 = imread("path", CV_LOAD_IMAGE_GRAYSCALE); after your comments I've tried with cvtColor() but the error was the same. descriptors_1 is not empty. Checked with .data and .empty().

The code is running, when both images are equalized.

Immi ( 2013-04-15 01:27:05 -0600 )edit

Ok out of ideas here :) all depends on @Guanta now :)

StevenPuttemans ( 2013-04-15 01:31:26 -0600 )edit

Hi, I've found the solution: http://answers.opencv.org/question/11449/flann-algorithm-cannot-find-any-descriptor/ I was using the same picture for img_1 and img_2

Immi ( 2013-04-15 01:50:29 -0600 )edit

Indeed, that is a frequent error also. Didn't think of it this time :) Good luck with your project. Accept the answer of guanta, so topic looks solved and maybe add the link and explanation to the problem at your original post.

StevenPuttemans ( 2013-04-15 01:53:41 -0600 )edit

I have still a question for this problem: When I'm equalizing both images, it works also with the same image file. Why does it crash, when I'm equalizing only img_1?

Immi ( 2013-04-15 02:02:15 -0600 )edit

No idea, what exactly crashes actually?

Guanta ( 2013-04-15 05:25:13 -0600 )edit

I'm just wondering about this error described in topic. It crashs equalizing one image. im1 = imread("im1.bmp, CV_LOAD_IMAGE_GRAYSCALE); im2 = imread("im1.bmp, CV_LOAD_IMAGE_GRAYSCALE);

equalizeHist(im1, im1); // then it crashs like described above. descriptors_2 is empty

//adding following line, it's working equalizeHist(im2, im2);

And now I'm asking, why this happens.

Immi ( 2013-04-15 05:54:53 -0600 )edit

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Feature Matching with FLANN Tutorial

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