how to convert 1 channel grayscale image into 3 channel?

I have to train my images through vgg16, for which i need to convert my 1 channel grayscale images to 3 channel. i have used rgbimage=I(:,:,[1 1 1]) also repmat, but when i apply this command it changes my image into binary. I just need to change number of channels by keeping it grayscale. Help please!

[Adam]

cat( 3, I, I, I )

should work, though looks ugly. Repmat, done correctly, should work too I would have thought. I imagine there is an Image Processing Toolbox function that does it though I can't remember off hand.

Answer 1

[Jan]

These are equivalent and working:

RGB = repmat(I, [1, 1, 3])
RGB = I(:, :, [1, 1, 1])
RGB = repelem(I, [1, 1, 3])

They do not change the class of the image or the values. Your impression, that this changes your "image to binary" is not correct. Either the observation is not correct or another command is responsible for the effect. Please post the relevant part of the code and mention, why you assume, that the image is changed.

[Saira charan]

I=imread('mdb120.png'); RGB = repmat(I, [1, 1, 3]) imwrite(I.*uint8(I),'mdb120.png')

Can you suggest what is wrong in this? My images are grayscale 1 channel. And using these commands does change it into 3 channel but the images are converted to binary. As i am dealing with mammograms i cannot get results from images that are just black n white. I hope i am clear now.

[Adam]

What is the range of I.*uint8(I)? If you plot I and plot that you should see if one or other is wrong before just saving them to file.