Diagonal direction - difference between adjacent elements

I have a matrix,

I =  5     4     3
     9     8     6
     6     3     4

How can I calculate differences between adjacent elements in a diagonal directions. I want these outputs(for first and last rows and columns I don't mind padding):

5     4     3
5     5     6
2    -3     4

and

 5     4     3
 9     3     2
 6    -6    -4

Answer 1

[Teja Muppirala]

Use 2-D convolution:

I = [ 5     4     3;
      9     8     6;
      6     3     4;]

I_1 = I;
I_2 = I;

I_1(2:end,1:end-1) = conv2(I,[0 1; -1 0],'valid')
I_2(2:end,2:end) = conv2(I,[1 0; 0 -1],'valid')