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colormap/caxis edit roipoly

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William on 20 Nov 2014
Edited: Charlotte Chaze on 20 Feb 2018
I would really appreciate help on this one,
Using roipoly to isolate data but when the function displays the initial image I want to draw on, the scaling is all wrong and it just shows a black image.
Applying colormap or caxis on figure editor shows the scaling is wrong but the below code does nothing. How can I set caxis on roipoly figure?
BW = roipoly(img)
colormap hot
caxis([0 1000])
Many thanks, Will


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Accepted Answer

Image Analyst
Image Analyst on 20 Nov 2014
Don't pass in img - I never do. Just set up the image in advance as far as how you want it to look.
imshow(img, []);
mask = roipoly;

  1 Comment

William on 20 Nov 2014
Fantastic, thanks :)

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More Answers (1)

Charlotte Chaze
Charlotte Chaze on 20 Feb 2018
Edited: Charlotte Chaze on 20 Feb 2018
The previously accepted answer doesn't work for me in R2017b - here is what does, using OP's example img.
When you use roipoly, it resets caxis to [0 1]. So just change the scale in your img to [0 1]. In this case, here are the series of commands you'd use:
Use 'caxis' to find out what the scale of your image is.
Say it's [0 1000]. This will give back
ans = [0 1000]
Now, divide your img by 1000 to reduce the caxis to [0 1]. Then use roipoly on that.
img = img ./ 1000
mask = roipoly(img)


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