May i know is it possible to convert an image from 101 x 101 uint8 to 101 x 101 x 3 unit8

The title tells thanks

Answer 1

[Stephen23]

Here is the simplest way to convert a 2D image to a 3D image:

rgbImage = grayImage(:,:,[1,1,1]);

[Image Analyst]

Interesting trick. I didn't expect that. I would have expected that when you tried to access the [1,1,1] plane when the third dimension does not yet exist would have thrown an error like this does:

a = [1,2;3,4]
b = a(:,:, 42);
Index exceeds matrix dimensions.
Error in test3 (line 2)
b = a(:,:, 42);

but it doesn't. I guess it's because you're using 1, and specifying a third index (dimension) to a 2D array is okay as long as it's exactly 1.

[Steven Lord]

Just about every array in MATLAB has trailing singleton dimensions. [There are a few exceptions, like some objects that overload and specialize indexing as well as function handles.] So the third dimension does exist, but it's usually not shown. That doesn't prevent you from explicitly asking for the SIZE in that dimension, or indexing with page indices from 1:size(a, 3) [which in this case is 1:1.]

 x = 5;
 size(x, 1234567) % returns 1

Here's an indexing example. Since I don't want to type over a million 1's I'll use a comma-separated list.

 ind = repmat({1}, 1, 1234567);
 x(ind{:}) % returns 5

A slightly smaller example, where I will type all the 1's:

 x(1, 1, 1, 1, 1, 1, 1, 1, 1, 1) % also returns 5

Answer 2

[Image Analyst]

Yes. Let's call your gray scale image grayImage. Then, to get a 3-D RGB image from it, use cat():

rgbImage = cat(3, grayImage, grayImage, grayImage);

If you want to do it while applying a colormap at the same time (which I don't think you do), then use ind2rgb():

rgbImage = ind2rgb(grayImage, yourColorMap);