## Derivative of affine transformation

Hi there,

I've got a problem, which need to solve the derivative of affine transformation.

For example, a 2D affine transform is:

$A_T(f_{x,y})=\left( \begin{array}{ccc}
a_{11} & a_{12} & a_{13} \\
a_{21} & a_{22} & a_{23} \\
0 & 0 & 1 \end{array} \right)
\left( \begin{array}{c}
x \\
y \\
1 \end{array} \right)=
\left( \begin{array}{c}
x^' \\
y^' \\
1 \end{array} \right)$

Here we got $a_{ij}$, which are 6 affine parameters. Then if we want to get the partial derivative of each parameter $a_{ij}$, which is:

$\frac{\partial A_T}{\partial a}$