Using cumulative density functions to adjust the histograms of an image.

Using the code below i am trying to match the Cumulative density functions of the grayscale gradient and the output image. i am having trouble with doing so.

All of the image arrays are in 16bit as i am hoping to use this code along side a series of 14bit grayscale images from a IR camera to adjust contrast and thersholds by adjusting the gradient array.

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures.
clear;  % Erase all existing variables.
workspace;  % Make sure the workspace panel is showing.
fontSize = 20;

inputImage=uint16(imread('cameraman.tif'));
inputImage=(5000+inputImage*3);
% Get the dimensions of the image.  numberOfColorBands should be = 1.
[rows columns numberOfColorBands] = size(inputImage);

% Display the original gray scale image.
subplot(3, 3, 1);
imshow(inputImage, []);
title('Input Image', 'FontSize', fontSize);
set(gcf, 'units','normalized','outerposition',[0 0 1 1]); % Maximize figure.
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off') 

% Let's compute and display the histogram.
[ipixelCount inputLevels] =imhist(inputImage , 65536);
subplot(3, 3, 2); 
bar(ipixelCount);
grid on;
title('Histogram of original image', 'FontSize', fontSize);
xlim([0 inputLevels(end)]); 

% Compute the CDF
icdf = uint16(65536*((cumsum(ipixelCount)  )/(sum(ipixelCount))));
subplot(3, 3, 3); 
plot(icdf);
grid on;
title('CDF of input', 'FontSize', fontSize);

Greyscalegradi = [rows , columns];
Greyscalegradi = uint16(Greyscalegradi);
X1=rows;
Y1=columns;
F=32768/X1;
G=32768/Y1;
for Y= 1:Y1   
    for X =1:X1
        Greyscalegradi (X,Y) = ((F * (X-1))+(G*(Y-1)));
        X=X+1;
    end
Y=Y+1;
end

% Get the dimensions of the image.  numberOfColorBands should be = 1.
[rows columns numberOfColorBands] = size(Greyscalegradi);

% Display the original gray scale image.
subplot(3, 3, 4);
imshow(Greyscalegradi, []);
title('Original Grayscale Image', 'FontSize', fontSize);
set(gcf, 'units','normalized','outerposition',[0 0 1 1]); % Maximize figure.
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off') 

% Let's compute and display the histogram.
[pixelCount grayLevels] =imhist(Greyscalegradi , 65536);
subplot(3, 3, 5); 
bar(pixelCount);
grid on;
title('Histogram of original image', 'FontSize', fontSize);
xlim([0 grayLevels(end)]); 

% Compute the CDF
cdf = uint16(65536*((cumsum(pixelCount)  )/(sum(pixelCount))));
subplot(3, 3, 6); 
plot(cdf);
grid on;
title('CDF of grayscale', 'FontSize', fontSize);

%tansfer function
Tcdf=(cdf);
% subplot(3, 3, 6); 
% plot(Tcdf);
% grid on;
% title('CDF of transfer grayscale', 'FontSize', fontSize);

% Equalize the image.
heImage = intlut(inputImage, Tcdf);

% Display the new gray scale image.
subplot(3, 3, 7);
imshow(heImage, []);
title('Equalized Image', 'FontSize', fontSize);

% Let's compute and display the histogram.
[pixelCountHE grayLevelsHE] = imhist(heImage, 65536);
subplot(3, 3, 8); 
bar(pixelCountHE);
grid on;
title('Histogram of Equalized Image', 'FontSize', fontSize);
% xlim([0 grayLevelsHE(end)]); % Scale x axis manually.

% Compute the CDF
cdfHE = ((65536 * (cumsum(pixelCountHE)  )/ (sum(pixelCountHE))));
subplot(3, 3, 9); 
plot(cdfHE);
grid on;
title('CDF of output', 'FontSize', fontSize);