ind2gray problem

Hello eveyone, I have a small problem using the function ind2gray. Here is the code I wrote :

figure(4);
hen = line(x(3:end-1),y(3:end-1),'linestyle','none','marker','.','markersize',0.001,'color','k');
pbaspect([1 1 1])
set(gca,'xtick',[],'ytick',[])
saveas(gcf,'henon.tif');
[henon,map] = imread('henon.tif');
henon2 = ind2gray(henon,map);

I get this error :

Undefined function 'ind2gray' for input arguments of type 'uint8'.

But in the matlab documentation for ind2gray it is written :

X can be of class uint8, uint16, single, or double. map is double. I is of the same class as X.

further more, when I type whos henon I get :

 whos henon
  Name         Size                 Bytes  Class    Attributes

henon      656x875x3            1722000  uint8

Is there something I am doing wrong ? I would like to simply create a grayscale picture from a figure. If anyone have a more simple way, please tell me ! Thank you.

[Guillaume]

It may be that the critical part of the error message is Undefined function 'ind2gray'.

ind2gray requires the image processing toolbox. Have you got that installed?

What is the output of

which ind2gray -all

[Stephen23]

romain dalidet's "Answer" moved here:

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Didn't knew that i needed image processinf toolbox ! Thank you for your anwser.

Do you know if there is another way for me to create a grayscale picture ?

Answer 1

[Guillaume]

Do you know if there is another way for me to create a grayscale picture ?

This can be achieved any number of ways. An easy one is to convert your image to RGB (which doesn't require the image processing toolbox) then to greyscale

greyimage = rgb2gray(ind2rgb(yourindexedimage, yourmap));

This may or may not produce the same results as ind2gray (haven't tested) since there is no unique way to convert from colour to grey scale.