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Image Processing...Please Help

Wed, 15 Jul 2009 21:03:29 -0700

Hello,

I am trying to write a matlab code to calculate the area of a specific region of a jpeg image using pixel size. To do so, I have two user defined functions. Users select these points by clicking on the image. The coordinates are then stored. I need to then apply a 2D median filter to create a binary image. I then need to use something (probably a while loop?) to detect the intensity edge of the image. The cut off intensity value would be the mean intensity of the image at the second user defined clicking point plus or minus 2 standard deviations. Intensity values below would be those found in this region. Intensity values above this cut off value would indicate the border/edge of the intensity at that particular y value. Then, it would record the x value at which the intensity difference happened in an array and move on to the next y coordinate value until reaching the upper y-coordinate limit (defined by the user click).

After obtaining this array between points (x1, y1) and (x2, y2), the distance between point (x1, y1) and (xa,ya) would be calculated using the distance formula (sqrt((x2-x1)^2=(y2-y1)^2)) until the distance reached an arbitrary value of 20 pixels. The value at which the distance is 20 pixels would be defined as the radius. The image should then be rotated by an angle defined by tan-1(|Yradius-y1|/|Xradius-x1|), to place this radius on a horizontal line with the initial user defined click.

After rotation, the same iteration process to find the intensity should be done for the image in this newly rotated state, except with the initial array varying in the x direction, and edge detection in the y-direction. Because here I need to calculate the area, after reaching the differing (higher) intensity value, I will need to count the number of pixels it took to get to this newly defined edge (in both the positive and negative direction). This will be done for each x value between the range of x1 of the user defined click, and the new radius coordinate point X. Then, to get the total distance (number of pixels) at each x value, I must find the distance between the y values.

Would anyone be able to tell me how to do/start tackling this task? I’m kind of new at this MATLAB thing.

Thanks.

Re: Image Processing...Please Help

Tue, 27 Oct 2009 18:31:57 -0700

Hi..

maybe this might help..
try to download the toolbox from this link
http://www.mathworks.com/matlabcentral/fileexchange/1596-imroi

i assume that you have already know on how to implement the toolbox in the matlab environment.

This toolbox helps me a lot when i'm tried to calculate the actual area of a specific regions. First, you have to try with your own image, then you have to click on the region or area that you want to trace. The final results will show you the area (in terms of pixels), mean, median and some statistics values based on the traced regions.

In my case, I have made some modification on the source code so that it fits to my image.. some unnecessary part is also removed.

OK, good luck!!!

-Salmah Yasiran-

Re: Image Processing...Please Help

Wed, 06 Jan 2010 03:00:52 -0700

Hi

I am working on my Project which needs to calculate the area of a Black and white image. I should calculate the area of the black object.

Can I use this toolbox to calculate the Area of the black object?
There is any tutorials how to use this Toolbox?

Regards,
Dominic

Re: Image Processing...Please Help

Wed, 06 Jan 2010 16:48:56 -0700

Dear Dominic,

Of course u can use the toolbox to calculate the specific area (black) that u want. I'll send an email to u on how to use the toolbox.. can u give me ur email?

Regards,
Salmah Yasiran

Re: Image Processing...Please Help

Wed, 06 Jan 2010 23:28:49 -0700

Dear Salmah Yasiran

Thanks a lot this is my email: abeladominic@yahoo.co.uk

Regards,
Dominic