Left Shifting the Histogram (Histogram Shifting) or Making the Image Darker / Less Bright using MATLAB
Yes making your histogram to shift left & making the image more dark or reducing the brightness are one & the same thing. Very easy to perform & you just need to apply some very basic arithmetic operation on the image. The operations could be either subtraction or multiplication with a constant less than 1.
For this article, we have taken a 640x640 grayscale image which is kept in the Current Working Directory. After opening it in MATLAB we will perform the further operations.
Histogram Left Shifting by subtraction of a constant:
MATLAB Code & Explanation:
%Suppose we are subtracting a constant value of 20 from each element of the grayscale image
%In the results it will be clearly visible that the image has become darker or less bright & the
%histogram is shifted to left side, & there are no values in the histogram for the value range 235-255
% i.e., at last 20 values in the histogram is vanished.
x=imread('new.jpg');
% if the image is not in the current working directory you need to specify the full path.
imshow(x);
%for showing the original image
figure,imhist(x)
%for showing the histogram of original image
n=x-20;
%performing the arithmetic operation on each element of the image & storing the result in new variable
figure,imhist(n)
%for showing the operated image
figure,imshow(n)
Results of The above MATLAB code of Left Shifting the Histogram using subraction
 |
| Original Unprocessed Image |
 |
| Histogram of Original Image |
 |
| Image After the arithmetic Operation (More Darker Than Original) |
 |
| Left Shifted Histogram after the subtraction operation on the image |
Histogram Left Shifting By multiplication of a constant less than 1 (<1):
x=imread('new.jpg');
% if the image is not in the current working directory you need to specify the full path.
imshow(x);
%for showing the original image
figure,imhist(x)
%for showing the histogram of original image
n=x*0.85;
%performing the arithmetic operation on each element of the image & storing the result in new variable
figure,imhist(n)
%for showing the operated image
figure,imshow(n)
Results of The above MATLAB code of Left Shifting the Histogram using multiplication
|
| Original Unprocessed Image |
|
| Histogram of Original Image |
 |
| Image After the arithmetic Operation (More Darker Than Original) |
 |
| Histogram of Processed Image |
Thanks a lot it is really helpful!
ReplyDeleteCould you Please give a hand with histogram shifting in image processing? I will use it to embedded data into an imege