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Convert an RGB image to grayscale but keep one color?

17 vues (au cours des 30 derniers jours)
Jaja
Jaja le 7 Sep 2014
Modifié(e) : DGM le 13 Fév 2023
A = imread('C:\FFOutput\gdgf\B.jpg'); B = rgb2gray(A); figure(1),imshow(B);
I have converted the image to a grayscale but don't know how to keep one color especially green.

Réponses (4)

yonatan gerufi
yonatan gerufi le 7 Sep 2014
Modifié(e) : yonatan gerufi le 7 Sep 2014
Hi, there are several ways to do it,
i find it easy to do:
red_color = A(:,:,1);
green_color = A(:,:,2);
blue_color = A(:,:,3);
  1 commentaire
Jaja
Jaja le 7 Sep 2014
how can I add this to my code to keep the green one? can you give me an example with the code??

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John
John le 7 Sep 2014
I am guessing you want the green channel stored in a separate matrix. In your code, A is only read. Its value does not change after the call to rgb2gray. To get the green channel from A:
greenChannel = A(:,:,2);
  1 commentaire
Jaja
Jaja le 7 Sep 2014
nothing happens actually. can you give me an example with the code??

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Image Analyst
Image Analyst le 7 Sep 2014
  3 commentaires
Jaja
Jaja le 25 Sep 2014
I actually want to keep the color green in the picture and the rest of the color is in the grayscale
Image Analyst
Image Analyst le 25 Sep 2014
Why? That's pretty much what the original image is already.

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DGM
DGM le 21 Oct 2022
Modifié(e) : DGM le 13 Fév 2023
Refer to this answer for more details on how this can be done. While that link includes multiple methods, I'm going to use MIMT replacepixels() for ease of use.
% this is a color image
rgbpict = imread('coloredChips.png');
% create a grayscale copy by some means
graypict = rgb2gray(rgbpict); % BT601 luma
% HSV ranges for masking
rangeR = [0.963 0.016; 0.258 1; 0.338 1];
rangeG = [0.380 0.453; 0.258 1; 0.338 1];
% create masks to select objects of specified colors
hsvpict = rgb2hsv(rgbpict);
maskR = all(hsvpict >= permute(rangeR(:,1),[2 3 1]),3) ...
| all(hsvpict <= permute(rangeR(:,2),[2 3 1]),3);
maskG = all(hsvpict >= permute(rangeG(:,1),[2 3 1]),3) ...
& all(hsvpict <= permute(rangeG(:,2),[2 3 1]),3);
% clean the masks
maskR = bwareaopen(maskR,100);
maskG = bwareaopen(maskG,100);
% composite the color and gray images using the masks
% replacepixels is from MIMT
outpictR = replacepixels(rgbpict,graypict,maskR);
outpictG = replacepixels(rgbpict,graypict,maskG);
See this answer for more details on how the masking could be done for this particular image.
See also this thread about different ways of partially desaturating a part of an image.

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