How can i convert set of images from RGB to Lab using matlab?

I have a set of images and I want to convert them from RGB to Lab , then i want to access and save L ,a,b values for each images .

Answer 1

[KALYAN ACHARJYA]

Read images from folder FAQ here

Before apply the code read here Representing color with the Lab color space

image_data= % Read the images form directory
for i=1:length(image_data)
% Read RGB Images
im_read=.....
lab_image=rgb2lab(im_read);
%save the lab image
end

[ahmad Al sarairah]

Should I use mean2 for each L,a, b values ? . I have used the below code :

for h=1:numel(I)

hmean(h) = mean2( I_hsv{h}(:, :, 1 ));

smean(h) = mean2( I_hsv{h}(:, :, 2 ));

vmean(h) = mean2( I_hsv{h}(:, :, 3 ));

LChannel(h) = mean2(I_Lab{h}(: ,: ,1 ));

aChannel(h) = mean2(I_Lab{h}(: ,: ,2 ));

bChannel(h) = mean2(I_Lab{h}(: ,: ,3 ));

end

Is this code correct for Lab values?

[Guillaume]

Yes, it's correct, but assuming all the images are the same size you'd be better off storing them all as one big 4D array:

Labimages = cat(4, I_Lab{:});  %better to construct it as a 4D array directly in the first loop, but otherwise you can do this

Then calculating the mean intensity of each the images is simpy:

Labmean = squeeze(mean(Labimages, [1 2]));  %requires R2018b. Earlier version: squeeze(mean(mean(Labimages, 1), 2));

which returns a 3 x numimage matrix of mean intensity.

[ahmad Al sarairah]

yes , all of the images are the same size . what do you mean by [1 2] ?

[Guillaume]

Take the mean across dimension 1 and 2 (rows and columns). This syntax is new as of R2018b.

[ahmad Al sarairah]

I am using matlab R2018a , Can I use this sentence?,or ,do I keep the same code that is currently used?

[Guillaume]

As I wrote in the comment:

Labmean = squeeze(mean(mean(Labimages, 1), 2));

in versions prior to R2018b

[Walter Roberson]

What execution error do you encounter?

[Walter Roberson]

What are you not using the loop control variable inside the loop?

[Walter Roberson]

Is the variable name I_lab or I_Lab or l_lab or l_Lab?

[ahmad Al sarairah]

Also , I need code to convert these same images from RGB to XYZ color space using loop

[KALYAN ACHARJYA]

XYZ color space?

[ahmad Al sarairah]

yes XYZ color space

[KALYAN ACHARJYA]

Rest loop operation is same

https://in.mathworks.com/help/images/ref/rgb2xyz.html

[Keerthi D]

I have a set of tomato diseased leaf images and I want to convert them from RGB to Lab , then i want to access and save a,b values for each images .how to do?

[KALYAN ACHARJYA]

1. Call the invividual image one by one

https://www.mathworks.com/matlabcentral/answers/393578-how-to-read-input-images-from-the-folder-sequentially

2. Convert RGB2 LAB

rgb2lab

3. Save the image or save in cell array (If it required in the next section of the code)

Regards

Kalyan