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video stream height measurement

Asked by M DINESH on 23 Jan 2013

i m working on video analysing program where i have to measure the height of the incoming video stream object, Now i took the video stream into the matlab. I couldnt do the measurement part .Can u pls help me with this analysing part.

4 Comments

M DINESH on 23 Jan 2013

the object will be in the same distance. The object height varies(withn the known region) and it has to be measured. The data has to be plotted in a histogram.

Jack Sparrow on 23 Jan 2013

I think you need to know atleast the intrinsic or extrinsic parameter of the camera or atleast have an object in the reference area. I'm currently working on something close to this for my M.Sc but i'm stalk at calculating the vanishing point in the image after getting the vanishing lines.

M DINESH on 23 Jan 2013

since my camera parameters are remain constant and also the reference object is located in the same distance. e.g.: I am lighting an candle from a fixed distance from a camera and i want to measure the height of the flame as a real time data. I m capturing the video and i m converting it to a image file and i m struck in measuring the flame height and plotted in an scaled graph like histogram

M DINESH

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3 Answers

Answer by M DINESH on 23 Jan 2013
Accepted answer

the object will be in the same distance. The object height varies(withn the known region) and it has to be measured.

0 Comments

M DINESH
Answer by Walter Roberson on 23 Jan 2013

Provided that the same aperture will always be used, since the object will always be at the same distance, the easiest way to proceed would be to start by inserting an object of known size into the scene, taking an image of it, and finding the height in pixels of the known real-world height. Once you have the height in pixels, you can trivially calculate a scaling factor between pixels and real-world.

After that, it just becomes a matter of figuring out the size in pixels of each presented object, and multiplying that by the real-world scale factor previously calculated. As long as nothing changes (e.g., distance does not change.)

16 Comments

M DINESH on 25 Jan 2013

kndly look into one of the image in below link.

http://imageshack.us/photo/my-images/855/20130125164432.jpg/

Walter Roberson on 25 Jan 2013

That seems to be an empty image.

Walter Roberson
Answer by M DINESH on 25 Jan 2013
Edited by Walter Roberson on 25 Jan 2013
im=imread('*.jpg');
red=im(:,:,1);
green=im(:,:,2);
blue=im(:,:,3);
light=red>200&green>200&blue>200;
[x,c]=find(light);
x2=max(x);
x1=min(x);
y2=max(c);
y1=min(c);
x2
774
x1
9
y2
765
y1
10
Warning: Image is too big to fit on screen; displaying at 56% scale.

this is the answer i got for pixel measurement.

13 Comments

M DINESH on 28 Jan 2013

whether the pixel measurement is right??????.

Walter Roberson on 28 Jan 2013
set(handles.staticText, 'String', num2str(x2));

I have not bothered to analyze the image you posted to figure out whether the pixel measurements are right. I suggest that you display the image and draw vertical bars at min(y) and max(y) to see whether the results look reasonable.

M DINESH on 11 Feb 2013

i have bought an video capture card and i m trying to install adapter in the matlab. i have used imaqregister ,but i couldn't get the dll file.

M DINESH

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