I'm trying to calibrate the integrated Camera of my notebook.
I'm using a 9x6 cheeseboard with a length of 300mm. It's printed on a Konica bizhub 452c and fixated on a drawingboard.
Using the tutorial-Code I'm getting strange undistorted Pictures, which shows that the calibration is bad (example below).
http://answers.opencv.org/question/64905/bad-camera-calibration/
I have feed about 70 pictures in the algorithm (different positions etc.) trying to get trainingpoints as far as possible to the picture edges.
I have tried for days to get an expectable calibration, but I'm only able to minimize the hole-effects on the sides.
Any Help would be appreciated.
If they are need I will provide the calibration-pictures.
regards
Moglei
I was having the same problem. I calibrated over and over again, but couldn't get any results better than the image you linked to, and sometimes worse. I read this question and answer from the OpenCV Q&A site, and it helped me solve my problem. In the link, you will see that the person answering the question writes that the problem is related to deficiencies in a couple of OpenCV functions that only become apparent when dealing with cameras with strong radial distortion. For me, I was able to "solve" the problem simply by zooming in. The "fish bowl" effect of radial distortion is most pronounced near the edges of the field-of-view, so by zooming in, you are effectively "cropping" your image and thereby reducing the extreme radial distortion. This may not be practical for your application, if you require the widest angle possible, or if your camera doesn't have zoom, but it worked for me!
This question is quite old, probably the issue has already been solved. I experienced the same issue with a wide-angle camera, my solution was to use a fisheye model that was able to correctly estimate camera intrinsics and lens distortions.
Related
What will be the procedure to correct the following distorted images ? It looks like the images are bulging out from center. These are of the same QR code, and so a combination of such images can be used to arrive at a single correct and straight image.
Please advice.
The distortion you are experiencing is called "barrel distortion". A technical name is "combination of radial distortion and tangential distortions"
The solution for your problem is openCV camera calibration module. Just google it and you will find documentations in openCV wiki. More over, openCV already has built in source code examples of how to calibrate the camera.
Basically, You need to print an image of a chess board, take a few pictures of it, run the calibration module (built in method) and get as output transformation matrix. For each video frame you apply this matrix (I think the method called cvUndistort()) and it will straighten the curved lines in the image.
Note: It will not work if you change the zoom or focal length of the camera.
If camera details are not available and uncontrollable - then your problem is very serious. There is a way to solve the distortion, but I don't know if openCV has built in modules for that. I am afraid that you will need to write a lot of code.
Basically - you need to detect as much as possible long lines. Then from those lines (vertical and horizontal) you build a grid of intersection points. Finally you fit the grid of those points to openCV calibration module.
If you have enough intersection points (say 20 or more) you will be able to calculate the distortion matrix and un-distort the image.
You will not be able to fully calibrate the camera. In other words, you will not be able to run a one time process that calculates the expected distortion. Rather - in each and every video frame, you will calculate the distortion matrix directly - reverse it and un-distort the image.
If you are not familiar with image processing techniques or unable to find a reliable open source code which directly solves your problem - then I am afraid that you will not be able to remove the distortion. sorry
First of all I'm a total newbie in image processing, so please don't be too harsh on me.
That being said, I'm developing an application to analyse changes in blood flow in extremities using thermal images obtained by a camera. The user is able to define a region of interest by placing a shape (circle,rectangle,etc.) on the current image. The user should then be able to see how the average temperature changes from frame to frame inside the specified ROI.
The problem is that some of the images are not steady, due to (small) movement by the test subject. My question is how can I determine the movement between the frames, so that I can relocate the ROI accordingly?
I'm using the Emgu OpenCV .Net wrapper for image processing.
What I've tried so far is calculating the center of gravity using GetMoments() on the biggest contour found and calculating the direction vector between this and the previous center of gravity. The ROI is then translated using this vector but the results are not that promising yet.
Is this the right way to do it or am I totally barking up the wrong tree?
------Edit------
Here are two sample images showing slight movement downwards to the right:
http://postimg.org/image/wznf2r27n/
Comparison between the contours:
http://postimg.org/image/4ldez2di1/
As you can see the shape of the contour is pretty much the same, although there are some small differences near the toes.
Seems like I was finally able to find a solution for my problem using optical flow based on the Lukas-Kanade method.
Just in case anyone else is wondering how to implement it in Emgu/C#, here's the link to a Emgu examples project, where they use Lukas-Kanade and Farneback's algorithms:
http://sourceforge.net/projects/emguexample/files/Image/BuildBackgroundImage.zip/download
You may need to adapt a few things, e.g. the parameters for the corner detection (the frame.GoodFeaturesToTrack(..) method) , but it's definetly something to start with.
Thanks for all the ideas!
with image processing libraries like opencv you can determine if there are faces recognized in an image or even check if those faces have a smile on it.
Would it be possible to somehow determine, if the person is looking directly into the camera? As it is hard even for the human eye to determine is someone is looking into the camera or to a close point, i think that this will be very tricky.
Can someone agree?
thanks
You can try using an eye detection program, I remember doing back a few years ago, and it wasn't that strong, so when we tilt our head slightly off the camera, or close our eyes, the eyes can't be detected.
Is it is not clear, what I really meant was our face must be facing straight at the camera with our eyes open before it can detect our eyes. You can try doing something similar with a bit of tweaks here and there.
Off the top of my head, split the image to different sections, for each ROI, there are different eye classifiers, for example, upper half of the image, u can train the a specific classifiers of how eyes look like when they look downwards, lower half of image, train classifiers of how eyes look like when they look upwards. and for the whole image, apply the normal eye detection in case the user move their head along while looking at the camera.
But of course, this will be based on extremely strong classifiers and ultra clear quality images, video due to when the eye is looking at. Making detection time, extremely slow even if my method is successful.
There maybe other ideas available too that u can explore. It's slightly tricky, but it not totally impossible. If openCV can't satisfy, openGL? so many libraries, etc available. I wish you best of luck!
I have a very specific application in which I would like to try structure from motion to get a 3D representation. For now, all the software/code samples I have found for structure from motion are like this: "A fixed object that is photographed from all angle to create the 3D". This is not my case.
In my case, the camera is moving in the middle of a corridor and looking forward. Sometimes, the camera can look on other direction (Left, right, top, down). The camera will never go back or look back, it always move forward. Since the corridor is small, almost everything is visible (no hidden spot). The corridor can be very long sometimes.
I have tried this software and it doesn't work in my particular case (but it's fantastic with normal use). Does anybody can suggest me a library/software/tools/paper that could target my specific needs? Or did you ever needed to implement something like that? Any help is welcome!
Thanks!
What kind of corridors are you talking about and what kind of precision are you aiming for?
A priori, I don't see why your corridor would not be a fixed object photographed from different angles. The quality of your reconstruction might suffer if you only look forward and you can't get many different views of the scene, but standard methods should still work. Are you sure that the programs you used aren't failing because of your picture quality, arrangement or other reasons?
If you have to do the reconstruction yourself, I would start by
1) Calibrating your camera
2) Undistorting your images
3) Matching feature points in subsequent image pairs
4) Extracting a 3D point cloud for each image pair
You can then orient the point clouds with respect to one another, for example via ICP between two subsequent clouds. More sophisticated methods might not yield much difference if you don't have any closed loops in your dataset (as your camera is only moving forward).
OpenCV and the Point Cloud Library should be everything you need for these steps. Visualization might be more of a hassle, but the pretty pictures are what you pay for in commercial software after all.
Edit (2017/8): I haven't worked on this in the meantime, but I feel like this answer is missing some pieces. If I had to answer it today, I would definitely suggest looking into the keyword monocular SLAM, which has recently seen a lot of activity, not least because of drones with cameras. Notably, LSD-SLAM is open source and may not be as vulnerable to feature-deprived views, as it operates directly on the intensity. There even seem to be approaches combining inertial/odometry sensors with the image matching algorithms.
Good luck!
FvD is right in the sense that your corridor is a static object. Your scenario is the same and moving around and object and taking images from multiple views. Your views are just not arranged to provide a 360 degree view of the object.
I see you mentioned in your previous comment that the data is coming from a video? In that case, the problem could very well be the camera calibration. A camera calibration tells the SfM algorithm about the internal parameters of the camera (focal length, principal point, lens distortion etc.) In the absence of knowledge about these, the bundler in VSfM uses information from the EXIF data of the image. However, I don't think video stores any EXIF information (not a 100% sure). As a result, I think the entire algorithm is running with bad focal length information and cannot solve for the orientation.
Can you extract a few frames from the video and see if there is any EXIF information?
I've 2 pictures of the same scene from an uncalibrated camera. The pics are from a slightly different angle and scale(zoom) and I'd like to superpose them, rejecting any kind of shake. In other words, I should transform them so the shake becomes imperceptible, do a Motion Compensation.
I've already tried using a simple SURF (feature) detector along with Homography but sometimes the result isn't satisfactory. So I am thinking about trying Image Rectification to compensate the motion.
- Would it work with slight changes, such as user shake?
- Would it really work to reject shake for these 2 frames? And for a bigger buffer of pictures (10 maybe)?
- Anyone knows if it would fix scale disparity (different zoom in the images)?
- What the algorithm really do? Will it transform both pictures into a third orientation?
If there is a better solution, I would be glad to know =)
EDIT
I don't aim to compensate blur motion but the displacement itself. For example, in this file the author compensates the angle difference between two cameras by Image Rectification. How does it actually work? Does it always create an intermediate picture orientation or can I specify that one of the pictures shall remains still??
Also, would I be able to apply this to many frames or it would always find an intermediate orientation for each two frames I put in?
Cheers,
I'm not sure how well superimposing the images would work. Another way to remove blur (including motion blur which should dominate in handheld camera devices) from an image is by blind deconvolution. It is basically a method of finding the inverse of the blur filter that was physically applied (camera shaken) to the real image. There's plenty of techniques out on the web. I've specifically had good results using a modified version of the algorithm in this paper: http://www.cse.cuhk.edu.hk/~leojia/all_final_papers/motion_deblur_cvpr07.pdf
It also comes with an executable file somewhere around the web so you can see if it's fit for your purpose.
Good luck out there!