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Thread Subject:
finding the corners of squares

Subject: finding the corners of squares

From: Leah

Date: 11 Jun, 2012 20:01:07

Message: 1 of 2

Hi,
I am trying to find the position of the 16 corners of the yellow post it notes in this picture:

http://oi47.tinypic.com/2566yvl.jpg

I have already cleaned up the image and changed it to a binary image.
Ibw_A = im2bw(A);
Ibw_A = imclearborder(Ibw_A);
Ibw_A = bwareaopen(Ibw_A,30);

I want to define a parameter in the matlab corner function or in this code, http://www.mathworks.com/matlabcentral/fileexchange/7652
which will require the corners to be at least 70 pixels apart.

Leah

Subject: finding the corners of squares

From: Ashish Uthama

Date: 12 Jun, 2012 12:52:55

Message: 2 of 2

On Mon, 11 Jun 2012 16:01:07 -0400, Leah <leahkrombach@gmail.com> wrote:

> Hi,
> I am trying to find the position of the 16 corners of the yellow post it
> notes in this picture:
>
> http://oi47.tinypic.com/2566yvl.jpg
>
> I have already cleaned up the image and changed it to a binary image.
> Ibw_A = im2bw(A);
> Ibw_A = imclearborder(Ibw_A);
> Ibw_A = bwareaopen(Ibw_A,30);
>
> I want to define a parameter in the matlab corner function or in this
> code, http://www.mathworks.com/matlabcentral/fileexchange/7652 which
> will require the corners to be at least 70 pixels apart. Leah

You will have to add the logic to filter out close points after calling
the CORNER (http://www.mathworks.com/help/toolbox/images/ref/corner.html)
function.

What would you expect if you have three points (imagine a isosceles
triangle) with the equal sides being 100 and the third side being 50.
Which corners would you want filtered out?

What is your end goal?

If your goal is to detect the yellow posits, you might be better off with
blob analysis
http://blogs.mathworks.com/pick/2009/11/06/segmenting-coinsa-tutorial-on-blob-analysis/
http://www.mathworks.com/help/toolbox/vision/ref/blobanalysis.html
  (regionprops to get the bounding box.)

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