Are there scale-relative coordinates in TikZ?

Whenever I change the text width in the following example, the \nodes seem to remain in a coordinate system which is independent of the scaling of the image. Is there a way to set the coordinates relative to the picture’s scale?

\begin{minipage}[t][][b]{0.38\textwidth}
\begin{tikzpicture}
    \node[anchor=south west,inner sep=0] at (0,0) {\includegraphics[width=1\linewidth]{images/Cones_2c.png}};
    \node [anchor=center] at (1.4,5.9625) {$\vec\omega_o$};
    \node [anchor=center] at (2.72,6.1375) {$\vec n$};
    \node [anchor=center] at (4.1125,5.9625) {$\vec\omega_r$};
\end{tikzpicture}
\end{minipage}