4.2 | 14 ratings Rate this file 206 downloads (last 30 days) File Size: 1.71 MB File ID: #17500

High accuracy optical flow

13 Nov 2007 (Updated 23 Jun 2009)

Code covered by the BSD License

High accuracy optical flow using a theory for warping

File Information
Description	This code implements two variations of the paper "High accuracy optic flow using a theory for warping" presented at ECCV 2004 by Dr. Thomas Brox. Its variants appeared in "Particle Video" presented at CVPR 2006 by Dr. Peter Sand. The files optical_flow_brox.m and optical_flow_sand.m are the files you need to run. optical_flow_brox.m implements the traditional algorithm. Just replace the first lines where images are read, with your image, and start the process. optical_flow_sand.m implements a variant presented in CVPR 2006. Again just replace the lines "img1 = imread('...')" and "img2 = imread('...')" with your images and the rest is automatic. The variable num_levels controls the number of images in the laplacian pyramid to be constructed. Change it to suit your convenience. The way to tweak / use the code is described in the documentation pdf that is attached with the code. It can also be accessed from http://perception.inrialpes.fr/~chari/myweb/Software/ In order to tweak the code, however, you need to read the two papers...
Required Products	Image Processing Toolbox
MATLAB release	MATLAB 7 (R14)
Zip File Content
Other Files	Flow/0144.ppm, Flow/0160.ppm, Flow/brox.zip, Flow/brox_zip/computePsidashFS_brox.m, Flow/brox_zip/constructMatrix_brox.m, Flow/brox_zip/gaussDeriv.m, Flow/brox_zip/gaussianRescaling.m, Flow/brox_zip/gaussianSmooth.m, Flow/brox_zip/image_warp.m, Flow/brox_zip/imgGrad.m, Flow/brox_zip/mywarp_rgb.m, Flow/brox_zip/optic_flow_brox.m, Flow/brox_zip/psiDerivative.m, Flow/brox_zip/resolutionProcess_brox.m, Flow/brox_zip/sor.m, Flow/brox_zip/split.m, Flow/car0.png, Flow/car1.png, Flow/flow_documentation.pdf, Flow/sand.zip, Flow/sand_zip/channels_new.m, Flow/sand_zip/computePsidashFS_sand.m, Flow/sand_zip/constructMatrix_sand.m, Flow/sand_zip/gaussDeriv.m, Flow/sand_zip/gaussianRescaling.m, Flow/sand_zip/gaussianSmooth.m, Flow/sand_zip/getalphaImg.m, Flow/sand_zip/image_warp.m, Flow/sand_zip/imgGrad.m, Flow/sand_zip/mywarp_rgb.m, Flow/sand_zip/optic_flow_sand.m, Flow/sand_zip/psiDerivative.m, Flow/sand_zip/resolutionProcess_sand.m, Flow/sand_zip/sor.m, Flow/sand_zip/split.m, Flow/Thumbs.db, license.txt

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Everyone's Tags	geometric t, geometric transformation, high accuracy, image processing, image registration, optic flow, optical flow
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Comments and Ratings (29)
14 Nov 2007	F Moisy	How to get started? Please provide some help and examples! I was not present at the ECCV 2004 conference so I don't know how to start with those 20 files. As it stands, this submission is useless.
15 Nov 2007	F Moisy	OK, I have seen the (little) help of the revised version of this submission, thanks ; however I think it should still be improved to be really useful to other users: a) changing the filenames directly in the script is awful: you can't automatize the processing for several files! Just make it a function, in the form M = optic_flow(IM1, IM2) b) It still does not work for me. optic_flow_sand returns the error message "??? Undefined function or method 'getalphaImg' for input arguments of type 'uint8'." and optic_flow_brox returns "??? Undefined function or method 'split' for input arguments of type 'double'." (I use Matlab 7.5). c) I understand that for copyright reasons you cannot include the two refered papers into the submission; however you should explain a little bit what does each algorithm. F.
15 Nov 2007	visesh chari	Hi Mr Moisy, Thank you very much for your comments. Have incorporated all of them in the current version. V.
20 Jan 2008	mathild L.	I am to some extent friendly with different optical flow and warping techniques and I think that this code is worth a PhD project. The algorithm makes use of high mathematical background. I myself could understand the flow of the codes in less than an hour without reading help! Ofcourse I do not recommend this code for those who are novice in the field of motion estimation and registration while the algorithm relies on newly developed penalizations and warping strategies. Thanks for sharing this, Visesh! Five stars from me!!
01 Feb 2008	Samuel Foucher	I think there is a bug line in gaussianRescaling line 31. This line: img_scaled = imresize(img_smooth, scale_factor, 'bilinear', 0); should be: img_scaled = imresize(img_smooth, [fix(size(img_smooth,1)scale_factor) fix(size(img_smooth,2)scale_factor)], 'bilinear', 0);
06 Feb 2008	Visesh Chari	Hi Samuel, I am using Matlab 7.0.0.19901 (R14). In this case the line of code I wrote and the one you have written given the same results. Is there something I am not following ? Is there a difference for different versions ? I do not have access to other matlab versions so I cannot be sure. Please let me know if I am missing something... Thanks, Visesh
16 May 2008	Christian B.	First of all, it is a great relief that finally someone published an implementation to some state-of-the-art optical flows. However, I am a little bit curious about your implementation. First there are some bugs in it. In the Sand-Version your most outer loop does not rescale your solution to the initial resolution of the input images, as your loop variable stops at 8 but should go to 1. A similar bug is in the brox version, where i stops at 1 but should stop at 0. I tried your implementation on the yosemite sequence but I got horrible results. Using the sand-version I got an angular error of 12 degree and using the brox-version I got an angular error of 20, which is one magnitude larger than it should be! I would be interested in the explanation for this, because it is rather strange. Did you already make tests with the yosemite sequence by yourself? Should one choose other parameters maybe? If so, what parameters work well for this sequence. Without comparable angular errors it is hard to decide, whether your implementation is correct.
05 Jun 2008	Konrad S.	Christian, on Yosemite I get the Sand&Teller version to an angular error of AAE=3.4 degrees and endpoint error of AEP=0.17 pixels, excluding a 10 pixel border (like most evaluations do to limit mean boundary effects). This is after fixing the bug mentioned in your posting, and setting parameters alpha_global=5; alpha_local=10; outer_iter = 20; inner_iter = 20; mu = 0.95; % mu ... pyramid scale factor, hardcoded in original source The errors are not quite as low as those reported by Brox, but competitive with other recent entries in the Middlebury flow evaluation. cheers, Konrad
07 Jun 2008	Hui Fang	Although there are a couple of bugs in it, it's a good implementation anyway. You need fix the bugs when you are trying to use it. The two parameters,the smoothness one and the gradient one, are very important.When I did an experiment for face tracking and I set the smoothness weight to a big value or a small value, the error is unbearable.But finally I got a reasonable result when the parameter of this one and the gradient one are set suitable for my sequence.
27 Jun 2008	visesh chari	Hi all, Thanks for your comments. I am sorry to have posted a wrong version of the code, hence the wrong limits for inner and outer iterations. I did not notice that while uploading. Thanks for pointing it out. I will upload the corrected version in some time. You are right about the parameters. They are very important, and have to be carefully tuned to get the desired results, as per the author. The algorithm I have coded differs from the original formulation in some of the boundary conditions and smoothing operations.. (will post a documentation about it in the next 2 months). This is possibly the reason why the figures reported in the literature are not achieved by this code. Otherwise the code follows the algorithm faithfully, to my knowledge. Also, do watch this space for a MEX version of the above algorithm. Its faster than the current version, with exactly the same results.
19 Sep 2008	shifang xu	It is a very usefull demo as a state-of-the-art optical flows method. Thanks for sharing it!
30 Oct 2008	Assaf cohen	Hello i have a question, can i use the mywarp() function for any U,V i have that wasn't comuted by the algorithm? i mean, U,V are calculated not through this algorithm, but i want to use the warp function, will it work? or this is specially designed for this algorithm?
01 Nov 2008	Visesh Chari	it should work, so long as u and v are formatted like those in my code, which is just two 2D arrays with flow values....
03 Nov 2008	Assaf cohen	Hi, i have a question: the registration is GREAT, but aventully i get an image that is not as "focused" as the original image, it looks like filtered with gaussian filter... so, the question is how can i obtain aventually the original imag warped, and not the im2_hr ? thank you very much
05 Nov 2008	Visesh Chari	Hi, the basic smoothing operation that is done in the algorithm is to reduce the effects of noise in the data, so it cannot be avoided. If you really have noiseless data, and do not need much smoothing, you can change the appropriate parameters. You can refer to my documentation, but will eventually have to tweak the code to reduce the variance of the gaussian used for smoothing. If this is not too urgent (u can wait a week or so), I should be able to post additional documentation material, which you can use...
05 Nov 2008	Assaf cohen	Thank you, i am waiting. can't i resize u and v a little bit to be bigger? in the end, the original image is 148*148 and the im2_hr is a little bit less, so i want to resize the u and v and then warp the original image?
29 Jan 2009	UMD Mishra	Brox implementation does not work. There is something wrong with it..
04 Mar 2009	Visesh Chari	can you tell me what doesnt work ? i have received no complains so far... may be you did not read the reference document i sent... if possible post the error so that i can check
22 Mar 2009	Mo Star	Thanks for sharing. very well documented and extermely useful.
01 May 2009	Assaf laufer	Great! do you have the implementation in c?
27 May 2009	Ayaz Ahmed Shaikh	Great work!! Hi Vishesh, When I run the simulation of brox, in the lower left corner of quiver plot, there is some additional unwanted vector fields, i want to cope with them, so do you have any idea how to cope and why the are occuring?
31 May 2009	Aaron DeBattista	Great Piece of Work !!!!
01 Jul 2009	Naveen	Really great work! I am using this code for few of my images. I am not able to get the (u, v) of the same dimension as that of input images. I am getting (u,v) equal to the next resolution in the pyramid dependng on the scale_factor I give. For Instance, If I am giving two 120120 images, scale_factor = 0.5, no. of levels = 3, I am getting final output (u, v) of the resolution 6060. How to obtain (u,v) in the resolution of input images. Am I wrong in specifying some parameters?
29 Jul 2009	Omid Aghazadeh	Great work. Thanks for sharing. Haven't gone through the documentation yet, but the preset configurations worked reasonably well.
31 Aug 2009	tlg	Hi. First of all thanks for your share. I am trying to understand your code and I am almost finished but 'constructMatrix' function is still waiting to be explored. Could you, if possible, give some explanations on construction of the matrices in this script.
01 Sep 2009	tlg
10 Oct 2009	Johan	Visesh, you mentioned a MEX version of the algorithm. Have you made it available somewhere? I'm trying to run it on rather large images, so I could appreciate some improved speed. Thanks.
30 Oct 2009	Visesh Chari	Hi Johan, I have the code, but its not documented yet... I could give it to you if you want to have a look, but I haven't thoroughly proofread it for bugs, and might not have time before december....
22 Feb 2010	Hu Yu	Very usefull tool ! I'm looking forward to a MEX version.

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Updates
14 Nov 2007	I am adding a screenshot of the results of the current algorithm/code.
14 Nov 2007	Updating information on how to get started.
15 Nov 2007	Added a some documentation.
23 Jun 2009	Updated with license removed

Tag Activity for this File
Tag	Applied By	Date/Time
geometric transformation	Visesh Chari	22 Oct 2008 09:34:44
image registration	Visesh Chari	22 Oct 2008 09:34:44
optical flow	Visesh Chari	22 Oct 2008 09:34:44
optic flow	Visesh Chari	22 Oct 2008 09:34:44
high accuracy	Visesh Chari	22 Oct 2008 09:34:44
image processing	Visesh Chari	22 Oct 2008 09:34:44
geometric t	Visesh Chari	22 Oct 2008 09:34:44

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