How to Calculate Total Variation (TV) of an Image? TV is L1 norm of gradient of an image. So we've to find gradient of the image (which is still matrix, right?). Then take the sum of absolute values of the gradient matrix (So now it must be a scalar, right?). 

Can I simply use imgradient function in matlab for first step? It gives two values magnitude and direction, so which one should I consider for next step?

After getting gradient matrix say Igrad, will just summing absolute values (sum(abs(Igrad(:))) give me TV? And it must be just a single scalar value right?

Thank you for reading. Keenly waiting for your reply.
The Total Variation of an image $I$ can be computed using two formulas:


$TV(I) = \sum_{x} \| \nabla I (x) \|_1 $ (anisotropic TV);
$TV(I) = \sum_{x} \sqrt{ \| \nabla I (x) \|_2^2 }$ (isotropic TV).


In practice, both formulas yield almost the same result.

Using matlab, what you propose implements the first formula, while the second one can be obtained by sqrt(gradI_x.^2 + gradI_y.^2).