How to find four coordinates of inner rectangle?

How to find the four inner coordinates of the white rectangle in matlab?

Answer 1

[Michael Haderlein]

vsum=sum(image,1);
hsum=sum(image,2);
top=find(vsum,1,'first');
bottom=find(vsum,1,'last');
left=find(hsum,1,'first');
right=find(hsum,1,'last');

[Ashwathy Dev]

can you explain?

[Ashwathy Dev]

[Michael Haderlein]

The edges of the rectangle are the first/last values where the sum of all values is larger than 0. So we sum up along each dimension and search the first/last value which is nonzero.

A comment on top/bottom: You might want to exchange these two as for images, the y axis is reversed.

[Image Analyst]

Ashwathy's "Answer", which he accepted instead of Michael's, moved here so he can accpet Michael's answer instead of his own:

How to find the coordinates of the inner rectangle of the above figure. I want this for license plate detection.

[Image Analyst]

Michael's reply moved from Ashwathyu's "Answer" to here:

So is the question still open? What exactly do you need anymore? If my answer doesn't work/fit/suffice, please tell us what exactly is the problem. If my answer is fine, please mark it as accepted. This way, nobody will waste time reading through questions which have already been answered.

Thanks!

[Image Analyst]

Michael, your top/bottom is correct - nothing to switch/reverse. For images, like arrays, the top line is 1 and increases from there, so your formula for top will give the correct line (row) number.