how to convert grey image to RGB

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mohd akmal masud
mohd akmal masud 2021-1-9
评论： Image Analyst 2023-2-28
Hi all,
i have 60 slice grey image. how want to convert to RGB image?
as attached is my grey image (grey.jpg). rgb.jpg is from internet what i want like.
this is my coding, but got error.
P = zeros(103, 103, 60);
for K = 1 : 60
K_file=30+10*K;
petname = sprintf('I%d.dcm', K_file);
P(:,:,K) = dicomread(petname);
scale = 130/103 ;
Pi(:,:,K) = imresize(P(:,:,K),scale) ; % where P is your 103*103 3D matrix
end
rgbImage = gray2rgb(Pi);
imshow3D(rgbImage)
this is my function
function [Image]=gray2rgb(Image)
%Gives a grayscale image an extra dimension
%in order to use color within it
[m n]=size(Image);
rgb=zeros(m,n,3);
rgb(:,:,1)=Image;
rgb(:,:,2)=rgb(:,:,1);
rgb(:,:,3)=rgb(:,:,1);
Image=rgb/255;
end
BUT GOT ERROR.
Unable to perform assignment because the size of the left side is 130-by-7800 and the size of
the right side is 130-by-130-by-60.
Error in gray2rgb (line 6)
rgb(:,:,1)=Image;
Error in sliderspect1 (line 12)
rgbImage = gray2rgb(Pi);
I THINK MY function gray2rgb wrong.
can some one help me?

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采纳的回答

Jan
Jan 2021-1-9
Your Pi is a [130 x 130 x 60] matrix, but your function gray2rgb() expects a 2D matrix as input. It is not clear how you want to convert the 60 layers of the image data to RGB channels.
Maybe you want:
[r,c,m] = size(Pi);
rgbImage = repmat(reshape(Pi / 255, [r, c, 1, m]), [1, 1, 3, 1]);
  2 个评论
mohd akmal masud
mohd akmal masud 2021-1-10
Hi Jan,
i have change my coding accordingly your suggestion. But my image still grey as picture attached.
clc
clear all
P = zeros(103, 103, 60);
for K = 1 : 60
K_file=30+10*K;
petname = sprintf('I%d.dcm', K_file);
P(:,:,K) = dicomread(petname);
scale = 130/103 ;
Pi(:,:,K) = imresize(P(:,:,K),scale) ; % where P is your 103*103 3D matrix
end
rgbImage = gray2rgb(Pi);
imshow3D(rgbImage);
below is my function i changed.
function [Pi]=gray2rgb(Pi)
%Gives a grayscale image an extra dimension
%in order to use color within it
[r,c,m] = size(Pi);
rgbImage = repmat(reshape(Pi / 255, [r, c, 1, m]), [1, 1, 3, 1]);
end
CAN HELP ME?
Jan
Jan 2021-1-10
Yes, of course the image is grey, because the original images contain the grey level information only. If the value of each pixel of the input is used for all 3 RGB channels, the output looks grey also.
Which information do you want to use to define the colors?

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更多回答（2 个）

Image Analyst
Image Analyst 2021-1-10
Try
function rgbImage = gray2rgb(grayImage)
cmap = jet(256); % Or whatever one you want.
rgbImage = ind2rgb(grayImage, cmap); % Convert gray scale image into an RGB image.
  8 个评论
显示 6更早的评论
john
john 2022-1-10
编辑：john 2022-1-10
how do i convert grayscale image to same color image but it should be an rbg image?
I tried the above function which u gave. My input was a grayimage with just 0 and 255 values when i used above function and runned the program it got converted to blue and brown. But i want the same original image but it should be an rgb so how do i get it?
Image Analyst
Image Analyst 2022-1-10
@john if you have an image with just 0 and 255, and use ind2rgb() then you will end up with an RGB color image with only two colors - those colors being cmap(1,:) and cmap(255, :), which I guess are ble and brown for the colormap you used. There is no way to get back the original true color RGB image from only a gray scale version of it. as you can imagine, there are nearly an infinite number of color images that could be made from it. You'll just have to save your original RGB image if you want it later in your program.

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Jamal Nasir
Jamal Nasir 2023-2-28
移动：Image Analyst 2023-2-28
there is no traditional method to convert gray image to color image
this need using machine learning for prediction the pixel value depend on the region in
similar sense
  1 个评论
Image Analyst
Image Analyst 2023-2-28
He has a 60 channel hyperspectral image, as you can see from his code. One can use one of the strategies in the attached paper to convert multiple spectral channels into an RGB image.

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