How can adjust luminosity with HSV?

Hello friends, I have a set of 20 color images and I want to implement some operations.but before working on these images, I must homogenize the luminance (HSV) someone can suggest me a way to do this. I have done the following code, anda I want get the array of all image luminance average, but my problem is since the image is obtained by a for loop when a try change the image in rgb2hsv give me this error

if true
  % code
  Error using rgb2hsv (line 59)
  MAP must be a Mx3 array.

    Error in teste (line 15)
    hsv =  rgb2hsv(a)
  end

the code :

if true
  % code
  clear all, close all, clc;
  imgDir = dir(fullfile('','/database/*.jpg'));
  outDir = '/resultados/';
  imgDimensao = length(imgDir);

    data =zeros(1,imgDimensao)
    for x = 1:length(imgDir)
    handles.images{x}=imread(fullfile('','/database/',imgDir(x).name));
    a =  imgDir(x).name;

    hsv =  rgb2hsv(a)
    a = mean2(a);
    data(x) = a ; 
end
data
mean2(data
  end

Answer 1

[Image Analyst]

THe badly-named "a" must be an RGB image, not a filename string. And don't use hsv as an image name since it's a built-in function.

rgbImage =imread(fullfile('','/database/',imgDir(x).name));
hsvImage =  rgb2hsv(rgbImage);
meanValues(x) = mean2(hsvImage (:,:, 3));

After the loop, you can get the overall mean by doing this:

meanV = mean(meanValues);

[Biza Ferreira]

thanks for your time and consideration