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[OpenCV] Re: Using webcam for sun tracking

 

hmm, I certainly wouldn't keep my webcam pointed at the sun for hours, but I haven't tested it out. You should use the Hough circles algorithm to detect a circle in the image, then you can quickly find its centre.

If you find that it's picking up circles other than the sun, just get the integral image within a few of the more popular circles and pick the brightest one.

If you have to take snapshots for hours, I'd recommend using Boost time libraries.

I'd also recommend that book mentioned - the one by O'Reilly.

You don't need to know anything about DirectShow.

good luck :)
--- In OpenCV@yahoogroups.com, "pradeeptumati" <ptumati@...> wrote:
>
> I am currently designing a solar tracker that takes a snapshot of the sun and analyzes its position in the sky (http://www.iaeng.org/publication/WCE2010/WCE2010_pp844-846.pdf). I have never developed webcam/machine vision based applications and so I need some advice on how to approach this issue; I learn things accordingly and get things going from there.
>
> I intend to put a webcam on a dual axis heliostat. This webcam takes snap shots of the sky at frequent intervals (say once every minute). The application that I intend to develop is supposed to analyze each snapshot, locate the sun and compute its centroid; it essentially identifies the brightest spot in the sky and tries to identify its shape (hopefully it is going to turn out to be a circle). Since this is a basic webcam application, I am assuming that I don't need to study machine vision algorithms etc… What topics should I learn to achieve this…? As far as I understand, I should learn how to interface a webcam using directshow and grab bitmaps…. How can I analyze the bitmaps…? There should be some algorithms to identify the brightest spot…. Can I use opencv for this? Are there any books that I should start off on this topic. I looked at some books in amazon; I just don't know where to start. Any advice is highly appreciated…
>
> BTW: Can webcams withstand the intensity of the sun if I directly point them towards the sun?
>
> Thanks,
>

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Re: [free-e-books] Tips to Beat Summer Heat ... Nice

 

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From: Dr. Farah <nmbbh@ymail.com>
To: "free-e-books@yahoogroups.com" <free-e-books@yahoogroups.com>
Sent: Sunday, June 16, 2030 7:26 PM
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Re: [OpenCV] How to convert the image of a binary curve into an ordered list of points?

 

use CV_APPROX_NONE instead of CV_APPROX_SIMPLE

On Wed, Jun 1, 2011 at 7:57 PM, Jean-patrick Pommier <pommier@rocketmail.com> wrote:
 

Dear all,
I have a numpy array:
[[1 0 0 0 0 0]
 [1 1 0 0 0 0]
 [0 1 1 0 0 0]
 [0 0 1 1 0 0]
 [0 0 0 1 1 0]
 [0 0 0 0 1 1]]
 and I'd like to extract a list of ordered coordinates according to the points  neighborhood to get something like

(0,0),(1,0),(1,1),(2,1),....(5,5)

I tried, from a python script:
# create the storage area
storage = cv.CreateMemStorage (0)
npimage=np.uint8(skelpart[1])
print "npimage:",npimage,npimage.dtype
image=array2cv(npimage)
print "np to cv",image
# find the contours
contours = cv.FindContours(image,
                               storage,
                               cv.CV_RETR_TREE,
                               cv.CV_CHAIN_APPROX_SIMPLE,
                               (0,0))
print "skeleton points",len(contours)
for i in range(len(contours)):
    print contours[i]

and the result was (not good):
npimage: [[1 0 0 0 0 0]
 [1 1 0 0 0 0]
 [0 1 1 0 0 0]
 [0 0 1 1 0 0]
 [0 0 0 1 1 0]
 [0 0 0 0 1 1]] uint8
np to cv <iplimage(nChannels=1 width=6 height=6 widthStep=6 )>
skeleton points 4
(1, 1)
(1, 2)
(3, 4)
(4, 4)

Thank you for any advice.
Regards
Jean-Patrick


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[OpenCV] accuracy of icvComputeProjectMatricesNPoints ?

 

Hi I 'm using icvComputeProjectMatricesNPoints() in a project but I don't know the accuracy of this method since it doesn't provide the error of computation.
Has anyone ever tested this function ?
I'm using opencv 2.29,the latest snapshot.

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[OpenCV] How to add new features to openCV

 

Hi, I am new to openCV and I have a question.
I assume opencv_haartraining uses Haar-like features. But I want to use other kinds of features rather than Haar features. Could you tell me how to do so? Thanks in advance

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[OpenCV] The problem of cross-compiling opencv-1.0.0 with ffmpeg

 

I have cross-compiled ffmpeg without errors, and put the ffmpeg headers and libraries into cross-compiling chain. However, when i configured cv-1.0.0 with option 'with-ffmpeg', the printed info showed as follow:
checking ffmpeg/avcodec.h usability... yes
checking ffmpeg/avcodec.h presence... yes
checking for ffmpeg/avcodec.h... yes
checking for avcodec_decode_video in -lavcodec... no

Video I/O ---------------------
Use QuickTime / Mac OS X: no
Use xine: no
Use ffmpeg: no
Use dc1394 & raw1394: no
Use v4l: yes
Use v4l2: yes

my configure codeline was :
./configure --host=arm-linux --without-gtk --without-carbon --without-quicktime --without-1394libs --with-ffmpeg --without-python --without-swig --enable-static --enable-shared --disable-apps CXX=arm-linux-g++ CPPFLAGS=-I/opt/EmbedSky/4.3.3/arm-none-linux-gnueabi/include LDFLAGS=-L/opt/EmbedSky/4.3.3/arm-none-linux-gnueabi/lib --with-v4l --prefix=/home/xiaofevg/cvlib-1.1.0
(the avcodec.h etc were under the derictory:/opt/EmbedSky/4.3.3/arm-none-linux-gnueabi/include and libavcodec.so etc were under the derictory:/opt/EmbedSky/4.3.3/arm-none-linux-gnueabi/lib

I guessed the problem may be that opencv is incompatible to ffmpeg i used, but I tried almost every different vesion of ffmepg, the problem was still:checking for avcodec_decode_video in -lavcodec... no
does any guys meet the same problem? how to resolve this problem?

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[free-e-books] Accreditation and certification

 

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