Hilbert metric and Hölder continuity

We prove several formulas for the Hilbert metric in the unit disk and apply these results to study quasiregular mappings of the unit disk ${\mathbb{B}}^2$ onto a bounded convex domain $D$. The main result deals with the Hölder continuity of these mappings with respect to Hilbert metrics of ${\mathbb{B}}^2$ and $D$. Also several open problems are formulated.