how to convert gray scale image into rgb image?

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ug on 1 Apr 2013
Commented: Image Analyst on 22 Sep 2017
my project is on iridiology...and it requires to convert the gray scale image to an rgb image to find the basic color of the iris. am in need of the code to convert the gray scale image to rgb image.
Image Analyst
Image Analyst on 22 Sep 2017
You should put this in the "Answer" section. Right below my Answer that says the same thing you just did.

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Answers (6)

Ahmed A. Selman
Ahmed A. Selman on 1 Apr 2013
Use colormap types, since you are interested with a colored region of interest, I think any colormap format suffices. Example:
close all
clc % just to clear things up
R=rgb2gray(I); % It is gray now
imwrite(R,y,'rgb.jpg','jpg'); % Re-change it to colored one
Image Analyst
Image Analyst on 2 Apr 2013
Of course. Wish you'd explained that initially. See my new answer.

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Image Analyst
Image Analyst on 1 Apr 2013
ug, if your starting image is monochrome, then you cannot determine the original color. You cannot. Not if all you have is the grayscale image. Period.
You can convert a grayscale image into an RGB image using cat():
rgbImage = cat(3, grayImage, grayImage, grayImage);
of course it will look all grayscale even though it is a "true color" RGB image - it's just that all the "colors" are gray. You can apply a pseudocolor lookup table to the gray values, where each gray value gets mapped into some color, to get a multi-colored image, like this:
rgbImage = ind2rgb(grayImage, jet(256));
however the colors are NOT the original colors of the iris as if you had snapped it with a color camera.
Image Analyst
Image Analyst on 2 Apr 2013
Like I said before see my new answer ( ind2rgb() doesn't apply anymore. You will not be using ind2rgb. Again, see my new answer above.

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Image Analyst
Image Analyst on 2 Apr 2013
You ask: "i hav an image of the iris with all extra features like eye lashes n all..i hav to extract only the iris frm tis image. first i select the two circles of the iris..the resultant image is that the coloured part of the iris is converted to gray scale n the rest is blacked out... but i want to get the original there ne other method to get the colour of the iris?"
Here's how to do it.
% Make a mask from your circle using poly2mask
% xCircle, yCircle are the coordinates of your circle perimeter.
mask = poly2mask(xCircle, yCircle, rows, columns);
% Now mask the image so that only the original RGB part
% inside the circle remains, and outside the circle is set to black.
maskedRgbImage = bsxfun(@times, rgbImage, cast(mask,class(rgbImage)));

Mahdi on 1 Apr 2013
Gabriel made a script for that. You can find it here.

ug on 1 Apr 2013
@Ahmed A. Selman
Am getting the following errors:
??? Error: File: C:\MATLAB7\toolbox\images\images\private\checkinput.m Line: 38 Column: 1
Incomplete or misformed expression or statement.
Error in ==> images\private\checkstrs at 26 checkinput(in, 'char', 'row', function_name, variable_name, argument_position);
Error in ==> imlincomb>ParseInputs at 95 output_class = checkstrs(varargin{end}, valid_strings, mfilename, ...
Error in ==> imlincomb at 83 [images, scalars, output_class] = ParseInputs(varargin{:});
Error in ==> rgb2gray at 58 I = imlincomb(coef(1),X(:,1),coef(2),X(:,2),coef(3),X(:,3), ...
Error in ==> trial at 5 R=rgb2gray(I); % It is gray now

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G.Liz on 31 Jul 2013
Does anyone know how to segment the sclera of the eye ?

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