Doomb0t's profile - activity

No esta un problema si tu Ingles esta mal, estamos entendiendo (mi espanol no esta bien tambien ;) )

ORB and BRISK are supposedly designed to run on low memory devices OR run faster on high end devices. They also are free of any patents whatsoever, contrary to SURF...

Thanks! Actually, I already know the area of each of my blobs, so right now I am able to pair them "by hand". I was just looking if there was an already made function in OpenCV instead of having to do it myself. It's Friday and I don't want to reinvent the wheel if possible :)

Well, actually I must do a comparative study between some methods such as ORB, BRISK, etc. and blob detection, over a wide range of synthetic and real life images, in order to characterize their functioning under some circumstances... This is in relation with my master's thesis. So it is normal that blobs won't work well in a lot of situations, but I need to show which ones...

Yeah, I know this is only relevant in some special cases. Right now, I use synthetic images that are simple enough for it to work...

Is there a ready made solution to match blobs (detected by the SimpleBlobDetector) the same way that one may match keypoint descriptors such as ORB in OpenCV?

I mean, when using the "detect" method of the blob detector, it stores the blobs as a vector of keypoints and, given that I used the relevant parameters, it gives me the area of each blobs. Now, I have two vectors of keypoints/blobs from two images and I want to match the blobs. Using something like knnmatch requires descriptors as inputs.

I thought of 2 possibilities, but I would prefer if there was something already optimized.

• Implement by myself the matching algorithm so that it takes as input two vector of keypoints and as output a vector of vector of DMatches (I don't trust myself to make this more efficient than a naive implementation) OR
• Create a routine that fills a mat of descriptors, with each areas encoded as a bit vector to make it look like a standard descriptors. Then use knnmatch.

Does anyone know of an alternative? Thanks :)

You might want to use binary descriptors such as ORB or BRISK http://docs.opencv.org/modules/featur... They are quite faster than SURF or SIFT, there are no patents on them! Usually the quality of the detection is similar or pretty close to SURF, but they are optimized to run fast on modern processors

Maybe change to k=1? in c++, K=2 means that you want the 2 best candidate matches for a specific feature...

Mmmm sorry that I don't have much time at hand right now, but it seems that you are confusing between a vector of vector of keypoints and a plain simple vector of keypoints. But I am unsure, if somebody else could check it would be great!

Do you really need 2 cameras? I mean, if you lay the fish flat on a table close to a ruler, then take a picture with a single camera, you can determine that 1 cm equals n pixels. So, finding the length would not be hard... Then we don't know if it possible for you to put the fish on a table ;)

First, you must understand that a MxNx3 in greyscale doesn't exist. I mean, the concept of greyscale is that you have one channel describing the intensity on a gradual scale between black and white. So, it is not clear why would you need a 3 channels greyscale image, but if you do, I suggest that you take the value of each pixel of your 1 channel greyscale image and that you copy it three times, one on each channel of a BGR image. When a BGR image has the same value on each channel, it appears to be grey. I don't program in Python so I can't provide a direct code...

That's it!

@StevenPuttemans @berak

You could look at this: http://www.mrpt.org/tutorials/mrpt-ex... This was not applicable for me but MAYBE it could fit your needs

findHomography's implementation in OpenCV comes with some assumptions behind. In the "standard" case of use, you detect keypoints (x,y coordinates) in two images. According to the comments, you get keypoints as coordinates of stars from another algorithm. Now, in the standard case, you compute a "descriptor" for each keypoint in both images. I don't want to delve too much in the details, but it is a way to almost "uniquely" distinguish a keypoint from another.

When you have computed all the descriptors, you use a matching algorithm to pair a keypoint from the first set of point to a keypoint from the second set. The matching algorithm often just compare all the descriptors and pair the most similar. A good proportion of actual outliers may be matched this way, but for the usual application it is okay. Then, you use findHomography as you did and usually, good results arise.

In OpenCV's implementation of findHomography, the assumption is that all the points in input set 1 are already paired with a plausible match in the input set 2. This is where I see a problem with your use of findHomography; I am not sure that you have some way to pair those plausible matches.

In the literature, algorithms exist to match two sets of (x,y) based on their coordinates. One of them is RANSAC, and it is used in findHomography, even if it is in a form not directly of use for you.

If you ever used Matlab, this library implements RANSAC and could be of use to you: https://github.com/RANSAC/RANSAC-Toolbox

For example, here is the tutorial suggested by OpenCV:http://docs.opencv.org/doc/tutorials/features2d/feature_homography/feature_homography.html#feature-homography

Could you explain/show how do you get your points (ReferenceImage_pts, ImageToRegister_pts) in the first place?

@AlexanderShishkov, I have a problem with my "normal" account, so I created a new one. http://answers.opencv.org/question/60...

Ok! In my case, I had email notifications turned on some time ago so it seems my address was correctly set up in the forum.

Ok, well I only had 406 karma so it's not that bad. nayway, I can access my former public profile to consult previous questions...

Thanks!

Yes! ^^ I have been away so I completely forgot to migrate my account to a more "standard" form.

An issue with the Google ID

what if the date is passed and I am unable to log in my OpenCV account?

Hi,

how may I contact the site admin in order to retrieve an account? It wasn't hacked, but I had an issue with my account and I don't receive anything from the account retrieval system (with the email address stuff). I checked my spam btw ;)

Thanks! :)