Coloring pixels with a specific color

Is it possible to create an image (like the original) in which only the desired pixels are colored?

For example, I want to color white only the pixels with the numbers 25 to 27 (present inside 'grayLevel'). Any ideas?

rgb = imread('example.jpg');

%% Matrix of pixels
Number_Of_Rows = height(rgb);
Number_Of_Columns = width(rgb);

grayLevel = zeros(Number_Of_Rows,Number_Of_Columns);
    
for Row = 1:Number_Of_Rows
   for Column = 1:Number_Of_Columns 
    
        grayLevel(Row,Column) = rgb(Row, Column);
       
   end
end

Answer 1

[Image Analyst]

You need to somehow get the gray scale image from the RGB image though, maybe like

grayImage = rgb2gray(rgbImage);

Then you can use imoverlay

mask = (grayImage >= 25) & (grayImage <= 27);
rgbImage = imoverlay(grayImage, mask, 'Color', 'w');

[Alberto Acri]

Thank you for your reply. How can I create mask in case I want to use values inside a vector?

For example: v = [25; 26; 27; 30]

[Image Analyst]

mask = (grayImage == v(1)) | (grayImage == v(2)) | (grayImage == v(3)) | (grayImage == v(4));
rgbImage = imoverlay(grayImage, mask, 'Color', 'w');

[Alberto Acri]

Is there any way to compact the line with mask?

[Image Analyst]

You could put it into a loop

mask = grayImage == v(1);
for k = 2 : length(v)
    mask = mask | (grayImage == v(k));
end
rgbImage = imoverlay(grayImage, mask, 'Color', 'w');

[Alberto Acri]

Thanks for the answer @Image Analyst! Whereas, if I have a V matrix of the type 3x2 where each row represents the coordinate of the pixel I want to color white? How can I do that?

[Image Analyst]

Try this

for k = 1 : size(V, 1)
    row = V(k, 1);
    column = V(k, 2);
    grayImage(row, column) = 255; % Or 65535 for uint16 images.
end

[Alberto Acri]

And how can I visualize them? Using for example 'imoverlay'?

[Image Analyst]

No, if you have a gray scale image and you just want white, not a "color", then you don't need imoverlay. You can just use imshow:

imshow(grayImage, []);