How to do standardization for the brightness and contrast of the image?

% Image Loading

a= imread('D01-1.jpg')

figure

imshow(a)

%Area definition

user_defined_ellipse = imellipse(gca, [10 10 275 275]);

wait(user_defined_ellipse);

MASK = double(user_defined_ellipse.createMask());

%mask

mask = uint8(MASK);

I = a.*mask;

figure

imshow(I)

title('comparison')

% Binary Image

Inew=im2double(I);

maxValue=max(Inew(:));

Inew(Inew == 0) = inf;

minValue = min(Inew(:));

Ibefore=im2double(I);

INew= imadjust(Ibefore, [minValue maxValue], [0 1]);

figure

imshow(INew)

title('adjusted')

INew2=im2uint8(INew)

figure

imshow(INew2)

title('adjusted2')

%Calculation

Bw1=I>0;

figure

imshow(Bw1)

title('Bond Area')

thresholdvalue=150;

Bw2=I>thresholdvalue;

figure

imshow(Bw2)

title('Intensity of IMC')

Bondarea = length(find(Bw1 == 1));

IMCArea = length(find(Bw2 == 1));

areaRatio = IMCArea/Bondarea*100;

fprintf('The area ratio is %0.2f%%\n', areaRatio) % %

As u can see here, i am using imadjust to adjust all my image from[min max] to [0 1] Then i use colour thresholding by selecting the value as 140 . Unfortunaly it does not work. Any way to adjust all the image to same contrast and brightness?