Undefined function 'rgb2gray' : Error using image function

Hi all, I am new to Matlab and have student version R2012a. I am trying to convert a color image to black and white. The error and code is listed below.

       I appreciate all  your help

Regards,

Amit Bothra

Error:

Undefined function 'rgb2gray' for input arguments of type 'uint8'.

Error in Week09_Program1 (line 4) Abw = rgb2gray(A);

My code:

clear all; close all; clc; A = imread('chacha','jpg'); size(A); Abw = rgb2gray(A);

[Jan]

Btw, omitting the "clear all" is a good idea, because there is no reason to remove all loaded functions from the memory. I assume, anywhere in the universe there is a dwarfish and evil teacher, who instructs the pupils to use clear all, most of all when posting code in a forum, to test when I desperate and give up mentioning this trivial but important detail.

@evil dwarfish teacher: I will be stronger!

@frequent contributors: Sorry that I repeat myself such frequently. It is not my intention to annoy you. I only want to save energy.

I wait for the day when a user finds out, that the code runs faster with this modification:

all = 7.0710678;  % <- magic accelerator!
clear all
...

Answer 1

[Image Analyst]

Type "ver" on the command line in the command window. Do you see the Image Processing Toolbox listed? Or you can run this code:

% Check that user has the Image Processing Toolbox installed.
hasIPT = license('test', 'image_toolbox');
if ~hasIPT
  % User does not have the toolbox installed.
  message = sprintf('Sorry, but you do not seem to have the Image Processing Toolbox.\nDo you want to try to continue anyway?');
  reply = questdlg(message, 'Toolbox missing', 'Yes', 'No', 'Yes');
  if strcmpi(reply, 'No')
    % User said No, so exit.
    return;
    end
end

[Amit bothra]

Thanks for your help.

 when i run the code i dont see any message on the Command window. However in the workspace hasIPT value is 1.

 Kindly guide.

ver command output:

------------------------------------------------------------------------------------------------ MATLAB Version: 7.14.0.739 (R2012a) MATLAB License Number: STUDENT Operating System: Microsoft Windows 7 Version 6.1 (Build 7601: Service Pack 1) Java Version: Java 1.6.0_17-b04 with Sun Microsystems Inc. Java HotSpot™ Client VM mixed mode ------------------------------------------------------------------------------------------------ MATLAB Version 7.14 (R2012a) Simulink Version 7.9 (R2012a) Control System Toolbox Version 9.3 (R2012a) Curve Fitting Toolbox Version 3.2.1 (R2012a)

[Image Analyst]

You do not have the Image Processing Toolbox so you don't have the rgb2gray() function. You can use the formula Jan gave as a replacement.

Answer 2

[Jan]

If you do not have the Image Processing Toolbox, you find e.g. this in the FileExchange: http://www.mathworks.de/matlabcentral/fileexchange/29392-rgb2gray.

But when you are in the net already, why not asking your favorite internet serach engine? You find even more useful source codes. E.g.:

GrayImg = uint8(0.2989 * Img(:,:,1) + 0.5870 * Img(:,:,2) + ...
                0.1140 * Img(:,:,3));