How can i Change pixel color?

Hello

I have a color image of type RGB and I need to change the color of each point (red, yellow, orange) to green. I hope that there is a programmatic solution to this problem.

[jonas]

What do you mean "of each point"? Better upload an example image and explain what type of output you're looking for.

[Ansam Nazar]

I mean I need amatlab code to convert every red or yellow or orange pixel into green pixel.

[Mehmed Saad]

Suppose i have a picture of size 400x400. When i import it in MATLAB (using imread or directly) the matrix size will be 400x400x3 uint8. Now the 3rd dimension depicts R,G and B. Now you can apply conditions on these three colors for 1 pixel and change there values as you want

For example True red is [255 0 0], now apply a check that if this condition satisfies change pixel to

[0 255 0]

[jonas]

Better replace loop by logical indexing and upload an example image.

[Mehmed Saad]

jonas is right, understand the code and try to replace for loops with logical indexing

Answer 1

[Mehmed Saad]

I = imread('red.jpg');
figure,subplot(121),imshow(I)
th = 20;
[x,y,~]=size(I);
for ii=1:x
    for jj=1:y
        if((I(ii,jj,1)-th)> I(ii,jj,2)&& (I(ii,jj,1)-th)>I(ii,jj,3))
            I(ii,jj,1) = 0;I(ii,jj,2) = 255;I(ii,jj,3) = 0;
            
        end
    end
end

subplot(122),imshow(I)

For same effect you can try this

I(ii,jj,1:2) = circshift(I(ii,jj,1:2),1);

I(:,:,1:2) = circshift(I(:,:,1:2),1,3);%without for loop

[Image Analyst]

Looks like you switched x and y. Usually it's good not to go against well entrenched naming conventions or else confusion will result. Remember, arrays are indexed (row, column) which is (y, x), not (x,y).

Also you can do it without loops like this:

rgbImage = imread('peppers.png');
subplot(2, 2, 1);
imshow(rgbImage);
title('Original Image', 'FontSize', 15);
% Split the RGB image into individual color channels.
[r, g, b] = imsplit(rgbImage);
% Define what is orange.
th = 20;
orangeMask = r > (g + th) & r > (b + th);
subplot(2, 2, 2);
imshow(orangeMask);
title('Orange Mask', 'FontSize', 15);
% Assign 0 to red and blue, and 255 to green to make those regions green.
r(orangeMask) = 0;
g(orangeMask) = 255;
b(orangeMask) = 0;
% Rebuild the RGB image from the individual color channels.
rgbImage = cat(3, r, g, b);
subplot(2, 2, 3);
imshow(rgbImage);
title('Altered Image', 'FontSize', 15);

[Mehmed Saad]

Thanks a lot Sir.

[Ansam Nazar]

Thanks alot for all of your help. but the function is not working in Matlab R2018a. the error was:

"Undefined function or variable 'imsplit'."

[Image Analyst]

You can do it manually:

r = rgbImage(:, :, 1);
g = rgbImage(:, :, 2);
b = rgbImage(:, :, 3);