# lsc directions

2021-04-17

Disentangling Images with Lie Group Transformations and Sparse Coding

Directions for future work…

# Background

We represent some image $I \in \mathbb{R^D}$ as

$$I = WR(s)W^T\phi\alpha + \epsilon$$

Where $\phi \in \mathbb{R^{DxK}}$ is our dictionary of templates and $\alpha \in \mathbb{R^K}$ is our code.

$$WR(s)W^T\phi\alpha + \epsilon$$

Few notes:

• Each template, or column of $\mathbb{R^{DxK}}$, has unit L2 norm. This ensures that each discrete pattern is qualitatively unique irrespective of scaling.

### Transform distribution proposal

We recognize that an overcomplete template basis necessitates learning smaller and more specific parts.

Perhaps we were able to learn a single transform on our composition of parts because each part was really a digit. And our code amounted to just choosing the correct digit.

With a true sparse-code, our parts will be more fickle, and we will want far more control over the manipulation of their poses for accurate reconstruction.

The following formulation is

Our objective is assign a transform $T(s)=W R(s) W^T$ to each template in $\phi$.

As a summation:

$$I = \sum_{k=1}^{K=20} \alpha_k W_k R(s_k) W_k^T \phi_k : W \in \mathbb{R^{Dx2}}$$