Increasing exposure of an image
94 views (last 30 days)
Show older comments
I have to increase the exposure of photo 2 so that it looks like it "whited out". How would I do this? The code I have below is on converting an image to grayscale.
The photos are also included in the zip file.
% Read the image 1
img1 = imread('photo1.jpg');
% Convert it to double
img1Double = im2double(img1);
% Convert from RGB to grayscale
img1Gray = rgb2gray(img1);
figure
imshowpair(img1, img1Gray, 'montage')
% Read the image 2
img2 = imread('photo2.jpg');
% Convert it to double
img2Double = im2double(img2);
% Convert from RGB to grayscale
img2Gray = rgb2gray(img2);
figure
imshowpair(img2, img2Gray, 'montage')
0 Comments
Answers (2)
Subhadeep Koley
on 15 Nov 2020
A simple approach could be adding a constant value to the entire image. Like below,
% Load the image
img = imread('photo1.jpg');
% Add a constant value to the image
overExposedImg = imadd(img, 100);
% Visualize them
figure
imshowpair(img, overExposedImg, 'montage')
2 Comments
Image Analyst
on 22 Mar 2022
That (addition) would produce a whiteout image, but a true overexposure like you'd get from increasing the exposure time on the camera would be closer to a multiplication by some factor. I think even that is not theoretically perfect because of a gamma that could be applied.
DGM
on 22 Mar 2022
Edited: DGM
on 22 Mar 2022
If it's assumed that the gamma correction is a simple power function, then the cheap solution would be to just apply the gamma to the multiplication factor instead of eating the cost of fractional exponentiation of the entire array.
A = imread('peppers.png');
k = 1.5; % intensity scaling
g = 2.4; % assumed gamma
A = im2double(A);
B = A*(k^(1/g));
B = im2uint8(B);
imshow(B)
Otherwise I suppose you could do the whole thing.
A = imread('peppers.png');
k = 1.5;
A = im2double(A);
B = lin2rgb(rgb2lin(A)*k);
B = im2uint8(B);
imshow(B)
See Also
Categories
Find more on Convert Image Type in Help Center and File Exchange
Products
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!