How to calculate entropy of color image in matlab?

I want to calculate entropy of color image. I found the command entropy(img) for the grayscale image. I dont know how to find entropy for a color image in matlab. Please help me.

[KSSV]

It accepts RGB matrix i.e 3D matrix too. But I am not sure of the value.

Answer 1

[Walter Roberson]

reshape() the image to a vector and call entropy on that.

[Aarach Sap]

a=imread('');
vec=a(:);
entropy(vec);

Done this but the entropy value is lower than I thought.

[Sadia Iffat]

What should i do if i want to calculate the entropy of the region of interest?

[Walter Roberson]

If you have a binary mask, then use it to index the image, and the result will be a vector; you can calculate the entropy of the vector.

[Image Analyst]

Like I said in your duplicate question

entropyWithinMask = entropy(grayImage(mask));