How to generate Reddish, Greenish, Blueish, and whiteish images using color images. I'm using this function. If its wrong please change it.

a=imread('fruit.png');

b=a;

a(:,:,2)=0;

a(:,:,3)=0;

subplot(2,2,1)

imshow(a)

[DGM]

Does the code do what you want it to do?

That's certainly one way to create a "reddish" version of an image, but I can imagine many other ways that would produce different "reddish" images. It all depends what you want.

Answer 1

[DGM]

There might be many ways to make a "reddish" version of an image. Consider the examples:

% i'm doing this in double for simplicity.
A = im2double(imread('peppers.png'));

% equivalent to 'multiply' (same as what you're doing)
B = A.*permute([1 0 0],[1 3 2]); 
imshow(B)

% equivalent to 'screen'
C = 1-((1-A).*(1-permute([1 0 0],[1 3 2])));
figure; imshow(C)

% simple weighted opacity blend
kalph = 0.5;
D = kalph.*A + (1-kalph).*permute([1 0 0],[1 3 2]);
figure; imshow(D)

% simple hue substitution
E = rgb2hsv(A);
E(:,:,1) = 0;
E = hsv2rgb(E);
imshow(E)

% combine luma with red overlay
F = repmat(rgb2gray(A),[1 1 3]).*permute([1 0 0],[1 3 2]); 
imshow(F)

These examples are simplified and use implicit array expansion (requires R2016b or newer). To change the color to green or blue (or any other color), simply change the [1 0 0] color tuple to something else. In the case of the hue substitution example, use 0.33 for green or 0.67 for blue.

This is a related question about creating a colorized version of an image:

https://www.mathworks.com/matlabcentral/answers/1610340-how-to-make-yellowish-image

[Kiha Kim]

Thanks!

[Kiha Kim]

Can I ask what is the code of whiteish?

[DGM]

I don't know what "whiteish" would mean in the case of 'multiply' or 'hue' blending. You never really clarified what you were after.

A = im2double(imread('peppers.png'));

% simple weighted opacity blend
kalph = 0.5;
D = kalph.*A + (1-kalph).*permute([1 1 1],[1 3 2]);
figure; imshow(D)

% simple saturation swap
% hsv is pretty terrible for S adjustments
E = rgb2hsv(A);
E(:,:,2) = 0;
E = hsv2rgb(E);
imshow(E)

% combine luma with white overlay
F = repmat(rgb2gray(A),[1 1 3]).*permute([1 0 0],[1 3 2]); 
% which simplifies in this case to:
F = repmat(rgb2gray(A),[1 1 3]);
imshow(F)