Error using label2rgb...

This error was occurred when I was testing the Example of the " Multilevel image thresholds using Otsu's method" in Matlab 2015a. Can you please tell me why this error occurred and how to solve this?

link to the example : -

openExample('images/CompareThresholdingEntireImageVersusPlanebyplaneThresholExample')

>> I = imread('circlesBrightDark.png');

>> imshow(I)

Warning: Image is too big to fit on screen; displaying at 67% 
> In images.internal.initSize (line 71)
  In imshow (line 305) 

>> axis off

>> title('Original Image')

>> thresh = multithresh(I,2);

>> seg_I = imquantize(I,thresh);

>> RGB = label2rgb(seg_I);

Error using label2rgb
Expected input number 1, L, to be two-dimensional.

Error in label2rgb>parse_inputs (line 128)
validateattributes(L,{'numeric','logical'}, ...

Error in label2rgb (line 49)
[label,map,zerocolor,order,fcnflag] = parse_inputs(varargin{:});

Answer 1

[Walter Roberson]

You need to convert your image to greyscale to use that function.

[thar]

I used the original image from the example by downloading it. DO i have to convert it to greyscale ?

This is the image i used

 http://in.mathworks.com/help/examples/images/SegmentImageIntoThreeLevelsUsingTwoThresholdsExample_01.png

[Walter Roberson]

Yes. Although the image only visually looks like grayscale, it is an RGB image.

[thar]

Thank you very much.

[ThankGod Alexander]

Thank you very much for this answer. I just encountered it and a quick search gave your answer and I was able to fix it