Tracing boundary in RGB image

I have a TIFF image that i have attached with this question (Picture1). I could not attach the TIFF format hence attached a JPEG format.

It is a random image. I want to convert it into boundary image, i.e. the different color parts are represented by just a boundary as shown in Picture 2.

Any help would be appreciated. I have MATLAB 2015a. I have tried using visboundaries but I could not convert my TIFF image into binary.

Answer 1

[Josh]

You just want the outlines of the colored regions stored in another image, right?

You can use the gradient function:

% Convert image to double (gradients are always returned as double arrays)
J = im2double(I);

% Loop through color channels (assuming original image is stored in I)
for i = 1 : 3
    G(:,:,i) = imgradient(I(:,:,i));
end

% Convert the gradient to grayscale and flip black and white
E = 1 - rgb2gray(G);