im2gray not working

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Preeti Sharma
Preeti Sharma 2022-6-8
评论： Preeti Sharma 2022-6-11
I am trying to read my image and to make it as an array. I want to use im2gray command but it is not working. However the same code with same image is working in matlab online and other systems. I have image processing software insatlled in the system. Please help me with this.
  2 个评论
KSSV
KSSV 2022-6-8
The error says im1 (image) is of class uint8 and im2gray is not working on that.
Try:
im2 = im2gray(double(im1)) ;
What version of MATLAB you are using? Actually im2gray should work for uint8 as well.
Preeti Sharma
Preeti Sharma 2022-6-11
I am using version 2020a. I tried and mat2gray worked perfectly. im2gray for the same image worked in version 2020b.

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回答（2 个）

DGM
DGM 2022-6-8
编辑：DGM 2022-6-8
im2gray() was introduced in R2020b. You're using R2020a.
Depending on what you need, you might be able to do it with rgb2gray() and some array size checks.
switch size(inpict,3)
case 3
outpict = rgb2gray(inpict);
case 1
outpict = inpict;
otherwise
% i'm assuming you don't want to support IA/RGBA images
error('a wild error message appears')
end
If you know all your images are RGB and aren't worried about running into ones that aren't, you can just use rgb2gray().
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Stephen23
Stephen23 2022-6-8
编辑：Stephen23 2022-6-8
"so every function in MATLAB/IPT that handles RGB images is latent buggy too."
Of course, the user must know what image type they have. My comment was more for the reader.
Ultimately an array of numbers is just that: any possible meaning it has can only be resolved at a higher level, as you very neatly put it.
DGM
DGM 2022-6-8
Apologies if I interpreted your comment as a message to me and not the reader/OP.
Either way, that blog post from Steve is good.

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Image Analyst
Image Analyst 2022-6-8
im2 = im1; % Initialize.
if ndims(im2) == 3
% If it's color, convert to gray scale.
im2 = rgb2gray(im2);
end
  2 个评论
DGM
DGM 2022-6-8
rgb2gray() accepts only mxnx3 arrays, but not all 3D images have 3 channels.
Image Analyst
Image Analyst 2022-6-8
@DGM correct. It assumes that the image im2 is a gray scale or RGB image. If im2 is a hyperspectral image or a volumetric image (like from CT MRI) then one should not use rgb2gray() or im2gray(). If you do an error will likely be thrown to alert you of that.

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