how can chose a fix rectangular in series of images that position may be changeable?

I have to extract the rectangle for a seris of images that the size of rectangular is 30*30 but the position of rectangular is changeable in every images. Is there any way? I know that I can use imcrop and getrect. but these command need xmin,ymin position. I just need to fix xwith and ywitd. Is there any way?

Answer 1

[Thomas Koelen]

imshow('pout.tif')
h=imrect(gca,[0 0 30 30]);
wait(h)

Gives you a draggable rectangle with xwidth and ywidth of 30.

[Image Analyst]

Then, if the size must remain 30 after the user is done interacting with it, to be robust you must find out the size they made it and then fix one of the corners and adjust the other corners to make sure the size is still 30x30.

[Thomas Koelen]

If this is the case, which corner would you use? How do you know where it went wrong? You can fix it by adjust a corner but you could also just force the widths to be 30 by doing this:

imshow('pout.tif')
h=imrect(gca,[0 0 30 30]);
pos=wait(h);
pos(3:4)=30;

would have the same effect but is easier.

[Image Analyst]

Yes, exactly. That will fix the upper left. Or you could use menu() to ask the user which corner to fix. Or you could just draw the box yourself with 4 calls to line() (to make sure it's always exactly 30 pixels), and then have two scroll bars on the GUI to let the user translate the box around.

[sara]

thanks Thomas Koelen and Image Analyst...but how can cut this segment that the coordinate preserved? can I use imcrop after this?

[Image Analyst]

Cut? What does that mean? And do you need to have the width be 30 after the user is done with it, or will you take whatever he made it?

Answer 2

[sara]

dear Image Analyst

I need to have the width be 30 after the user is done with it. you have a demo in this link http://www.mathworks.com/matlabcentral/answers/86477-how-to-isolate-certain-part-of-image at the of this page I find a code that when I run it, the result is like below:

I want to have a fix size square (30*30) that user can change the coordinate and has a result like below...i mean crop image with original coordinate. I hope that I could explain my opinion.