RGB and LAB values

The RGB values and LAB values of a particular location on an image will be different. How can I display these values ? Should I find RGB value of the location first and then convert it into LAB color space, or is there any other way?

Answer 1

[Constantino Carlos Reyes-Aldasoro]

RGB, LAB, HSV and many others are colour spaces, that is how to create colours that resemble what natural colours are, see for instance

https://en.wikipedia.org/wiki/Color_space

https://en.wikipedia.org/wiki/List_of_color_spaces_and_their_uses

Images from cameras will come as RGB in most cases, that means that every pixel has 3 values for the intensities of Red, Green and Blue channels. These will be different from LAB or any other colour space.

How can I display these values ?

Well, if you want to visualise as an image, then use imagesc or imshow where the three values will be interpreted as colour. You may want to visualise them separately as

imagesc(your_image(:,:,1))  %assuming that your image is called your_image

You may want to view the values so just type a range in the command window

your_image(1:5,1:5,1:3)

do not use semicolon in the end to echo to the screen the values.

Should I find RGB value of the location first and then convert it into LAB color space, or is there any other way?

you can convert the whole image in a single command:

your_image_LAB = rgb2lab(your_image);

Hope this helps. If this solves the problem, please accept the answer, if not, let me know.

[AKG]

I have an image. I want to display the RGB and LAB values of various locations of that image.

[Constantino Carlos Reyes-Aldasoro]

This will display the combination of RGB as colour:

imagesc(your_image)

if you want to see individual channels do this

subplot(311); imagesc(your_image(:,:,1));
subplot(312); imagesc(your_image(:,:,2));
subplot(313); imagesc(your_image(:,:,3));

be careful with the colour map you use, the safest is gray, but others may be better for visualisation.

And the same for the LAB

subplot(311); imagesc(your_image_LAB (:,:,1));
subplot(312); imagesc(your_image_LAB (:,:,2));
subplot(313); imagesc(your_image_LAB (:,:,3));

Answer 2

[Hrishikesh Borate]

Hi,

I understand that you want to display LAB color space values. By default, the Image Processing Toolbox represents colors in RGB values, but to get LAB values, rgb2lab function can be used.

For more information, refer to color space conversion.