Luminance correction for colored images using SHINE toolbox

Question

Wieke van Leeuwen 2016-7-4

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https://ww2.mathworks.cn/matlabcentral/answers/293650-luminance-correction-for-colored-images-using-shine-toolbox

编辑： Rodrigo Souza 2019-1-28

Unable to create colored images with equalized luminance with SHINE toolbox (images I've put in the input folder are colored, however the images in output folder are in grey scale), no error is given.

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Answer 1

Rodrigo Souza 2019-1-28

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https://ww2.mathworks.cn/matlabcentral/answers/293650-luminance-correction-for-colored-images-using-shine-toolbox#answer_358404

编辑：Rodrigo Souza 2019-1-28

Hi all,

I have put together three scripts for calculating (mean and SD), matching or normalizing luminance of colored images (using HSV and CIE Lab color spaces).

They may be specially useful for pupillometry measures of infant research.

The scripts and their descriptions are available at my OSF page: https://osf.io/auzjy/

Hope it helps.

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Answer 2

Image Analyst 2016-7-4

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https://ww2.mathworks.cn/matlabcentral/answers/293650-luminance-correction-for-colored-images-using-shine-toolbox#answer_227622

编辑：Image Analyst 2016-9-19

I've never heard of the SHINE toolbox. It's not one that the Mathworks sells. Do you have a reference?

To equalize luminance, convert to hsv or lab color space, then set the L or v channel to a constant, then convert back to rgb color space.

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ANA BUJAN 2016-9-20

在 MATLAB Online 中打开

I've also changed your code in order to include the calculation of the meanLuminanceValue, but as I'm very new in this field, I'm not sure my code is ok. I have run it, and no errors were given, but I'm not very confident about the results. In fact, the new images have a white background instead transparent, and even one of the images has a black backgorund. I'm sure I have a lot of mistakes.

I'm copying the code below:

images = dir('C:\Users\USUARIO\Documents\MATLAB\Images1\*.png')
for i=1:numel(images) 
file_name=dir(strcat('C:\Users\USUARIO\Documents\MATLAB\Images1\')); 
  rgbImage=imread(strcat('C:\Users\USUARIO\Documents\MATLAB\Images1\',images(i).name))
  labImage = rgb2lab(rgbImage);
  thisLuminanceImage = labImage(:,:,1);
  thisLuminanceValue = mean2(thisLuminanceImage);
  meanLuminanceValue = mean (thisLuminanceValue);
  % Scale luminance values (not replace with mean - it's different!).
  newLuminanceImage = thisLuminanceImage * meanLuminanceValue / thisLuminanceValue;
  labImage(:,:,1) = newLuminanceImage;
  rgbImage = lab2rgb(labImage);
  % Save new image
  imwrite(rgbImage,['C:\Users\USUARIO\Documents\MATLAB\Images1\', 'NEW',num2str(i),'.png']);
end

Thanks in advance.

Ana

Image Analyst 2016-9-20

Your code where you computed meanLuminanceValue is not correct. It's just computing the mean of the current image, not of the reference/background image.

Also attach a background image(s) that you use to compute meanLuminanceValue as well as an image or two that you wish to correct/alter to match the luminance of your reference/background images.

ANA BUJAN 2016-9-21

Many thanks for your patience. Yeah, that was the reason why the images remained the same... Nevertheless, I'm not using a specific set of images for computing the meanLuminancevalue, instead I would like to use the whole set of images for doing that. Then, the reference images for computing the mean and for matching the luminance are the same.

I'm attaching five images from my set. Again, thank you.

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