[Help] Webcam Image distance measurement?

[M3rcY]

Hello, 

I got a project which i have to finish by friday , but i m stuck and i dunno how to do it ?

i have a A4tech webcam and i want to capture images from that camera to labview and then measure the distance of things shown in the image from the webcam. any help would be appreciated .. if u dunno how to measure distance can u tell me something other than that which is closer , like how much each colour is there in the picture , actually i want to demonstrate a webcam and some measuring stuff.

Any help will be appreciated.

Thanks in advance

[pallen]

Hi there,

 

In order to get some meaningful help, you should provide a little more background about what you have tried so far, and what your results have been.  

Are you able to capture images?  

What tools are you using?  (Vision Builder, Vision Assistant, etc.)  

Measuring distances in the captured image is possible once the image has been calibrated.  There are several examples on image calibration.  

However measuring an object's distance from the camera is quite a bit more difficult.  I'm sure there is a way to do it.  But I would try starting with just measuring your object first.  

[M3rcY]

Hmm, well to tell u the truth , i m a total beginner at Labview , and thats y i dunno how to get started , can u plz guide me how to do it ? i have  a A4Tech 1.3 Megapixel USB Web cam , and i have Labview v8.6 , can u plz guide me , from where to begin, and how to measure image distance , the image size or something , any thing would be helpful.

[Cory_K]

Its hard to determine a distance only using 1 camera.

It would be easier to use two cameras, then use a little geometery to determine the distance.

That is why you have two eyes

[M3rcY]

ok, no problem i will get another camera , but tell me how to do it 😄 , i m totally stuck :$

[Cory_K]

Can the camera move?

Set the two cameras X distance apart.

Then, the first camera will turn A degrees, and the second will turn B degrees, until they are both focused on the object.

You then have two angles, and a length of a triangle.

You can use the Law of Sines to find the distance from either camera.

In terms of coding, I agree with Patrick Allen that you will need to use the 'Calibration' VI's under the 'Vision Utilities' menu

Message Edited by Cory K on 04-02-2009 11:14 AM

[M3rcY]

sounds good,

i will try that , but first can u plz tell me how can i acquire image from my web cam ? and what processing will be needed to calculate distance from those cameras

[Cory_K]

To aquire an image, under NI-IMAQ:
a) use 'IMAQ snap' to take a single image, like a photo

b) use 'IMAQ grab' to take continuous images, like a video.

b should be used in combination with 'IMAQ grab aquire'

To measure distances:

You would use the function under 'Vision Utilities', 'Calibration'.

I personally have never used these functions, so I cant really give you much help from there, sorry

[M3rcY]

Thanks man u r the best,

well after reading ur msg i thinks its pretty easy to measure image distance from the cam , but then a thing rings in my head

 why the hell then my teacher gave me the hardest project and he even challenged me that u wont be able to do it and if u r able to do it i will give u full marks . do u really think its that easy ? Thanks again , i will try IMAQ to take images from a single cam.

Wish me luck and any other advice for me on measuring the image ? and if i want to measure the amount of colours in the snap how to do it ? for example, i took of photo of mine , i have black hairs , so how to measure how much black colour is in the snap in total ? 

[Cory_K]

Hehe, good luck with your project

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M3rcY wrote:

... if i want to measure the amount of colours in the snap how to do it ? for example, i took of photo of mine , i have black hairs , so how to measure how much black colour is in the snap in total ? 

---

For this, I would recommend 'IMAQ ColorMatch'

You can find it here:

Vision & Motion >> Image Processing >> Color Processing >> IMAQ ColorMatch

It takes an input of an image, and a color (along with other things)

and outputs a "score", where a score is 0, no match, to 1000, perfect match

Message Edited by Cory K on 04-02-2009 11:46 AM