Finding coordinates of a rectangle in a picture

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Alice
Alice 2016-10-3
回答： Mihaela Duta 2016-10-11
I'm running an eyetracking experiment. I display an image using the Screen function from psychtoolbox and I want to know the coordinates of some of the items displayed in the picture. Is there a way of drawing a rectangle on the positions you want to find the location of? Or is there another way of doing it? Thanks.

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回答（3 个）

KSSV
KSSV 2016-10-3
You can draw rectangle using imrect.
doc imrect.
You can interactively pick the coordinates from the plot/ figure using ginput().
doc ginput.
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Alice
Alice 2016-10-4
What do the x and y coordinates that you get from ginput relate to? Are they pixels, or are they just coordinates on an arbitrary scale?
KSSV
KSSV 2016-10-4
They are the coordinates/ locations where you have clicked.

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Ann G
Ann G 2016-10-3
You can use the ginput and save the coordinates x,y by choosing the items.
[x,y]=ginput;
save x
save y
Mihaela Duta
Mihaela Duta 2016-10-11
编辑：Mihaela Duta 2016-10-11
I would suggest to use an image processing package to identify the areas of interest in your picture. You can use Adobe Photoshop if you have it, but gimp is an excellent free alternative (https://www.gimp.org/).
I am not sure whether you want to use these regions of interest when displaying the picture during the experiment, or for data processing. If you want to highlight regions of interest during the stimuli presentation, you can do that using the FrameRect function from Psychtoolbox.

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