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

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ahmad Al sarairah 2020-1-20

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评论： KALYAN ACHARJYA 2020-8-22

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 .

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KALYAN ACHARJYA 2020-1-20

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编辑：KALYAN ACHARJYA 2020-1-20

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

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ahmad Al sarairah 2020-1-22

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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 2020-1-22

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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 2020-1-22

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编辑：ahmad Al sarairah 2020-1-22

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

Guillaume 2020-1-22

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

ahmad Al sarairah 2020-1-22

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编辑：ahmad Al sarairah 2020-1-22

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

Guillaume 2020-1-22

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As I wrote in the comment:

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

in versions prior to R2018b

Walter Roberson 2020-1-23

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What execution error do you encounter?

Walter Roberson 2020-1-23

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

Walter Roberson 2020-1-23

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

ahmad Al sarairah 2020-1-23

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

KALYAN ACHARJYA 2020-1-23

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XYZ color space?

ahmad Al sarairah 2020-1-23

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yes XYZ color space

KALYAN ACHARJYA 2020-1-23

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Rest loop operation is same

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

Keerthi D 2020-8-22

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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?