Increasing exposure of an image

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')

Answer 1

[Subhadeep Koley]

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')

[Image Analyst]

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]

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)

Answer 2

[DGM]

There's a decent answer here:

https://www.mathworks.com/matlabcentral/answers/499576-increase-exposure-of-an-image-by-a-certain-number-of-stops-ev