How to Select Square Section of Image Interactively (not programmatically)

I am making a MATLAB App / GUI where a user selects an image, then will need to select a square section within that image (then other stuff using just this selected section). The size and location of the square will be different for each case.

I have been looking at options such as drawrectangle ( https://www.mathworks.com/help/images/ref/drawrectangle.html ), but I don't see a way to enforce the region selected is a square.

Of course, a rectangular section could be modified by trimming off excess pixels to make it a square programmatically, but that could affect the center of the region. I was thinking about using ginput to select a center location, then defining a square size that would lie on that center location..

Does anyone have a suggestion for a better way to select a square section of an image?

Answer 1

[Payas Bahade]

Hi Darren,

You can use drawrectangle function and pass following name-value pairs to ensure ROI is a square:

1. ‘AspectRatio’ which is ratio of height/width of rectangle and define value as ‘1’
2. ‘FixedAspectRatio’ to ensure that defined aspect ratio is fixed while interacting with drawn ROI and set its value as ‘true’

rect = drawrectangle(app.UIAxes,'AspectRatio',1,'FixedAspectRatio',true);

For more details, please refer this documentation link on customizable rectangular ROI.

Hope this helps!

[Darren Miller]

Perfect! Thank you