Merge RGB image and grayscale image MATLAB

Hi Guys. I have a grayscale image with size of 256*256. Pixels are shown in black, white,gray. Now I want to make the center pixel to red, but other pixels remain the same to before. Anybody can help me?

Thanks a lot.

Answer 1

[Guillaume]

rgbimage = repmat(yourgrayimage, [1 1 3]);
rgbimage(floor(end/2), floor(end/2), :) = [1 0 0];  %if image is of class double; [255 0 0] if uint8

[Penny]

Hello Guillaume, thanks for you answer. But in this case, we have a problem. Though the center pixel is changed to red, the other pixels are not shown like before. I want other pixels still shown as the grayscale image. Can we do this? Here is the image that the center pixels is red.

[Guillaume]

What is the class of your original image, what is the range of gray values in that image, what exact code did you use to set that red pixel and what exact code are you using to display the image?

The result you show would happen if the range of grey values in your original image was 0-255 and yet your image was of type double (it should be uint8 if intensity range is 0-255) and you use plain imshow(rgbimage) to display the image.

If that is the case, then assign [255 0 0] to that centre pixel and use imshow(rgbimage, []).

[Penny]

Hello Guillaunme, I did it by using overlay code, because that is what I actually want. Thanks very much for your answer.