矩阵图中的轮廓

Question

是否可以在通过阈值分隔区域的显式矩阵图中添加轮廓（例如使用 countours gnuplot）？请参阅 MWE 中手动添加的红线作为所需行为。

\documentclass{standalone}
\usepackage{pgfplots,pgfplotstable}
\usepgfplotslibrary{colormaps}
\pgfplotsset{compat=newest}

\begin{filecontents}{dataTest.txt}
    X,Y,Z
    0.1,0.1,2
    0.1,0.2,2
    0.1,0.3,2
    
    0.2,0.1,0
    0.2,0.2,2
    0.2,0.3,2
    
    0.25,0.1,0
    0.25,0.2,2
    0.25,0.3,2
    
    0.3,0.1,0
    0.3,0.2,2
    0.3,0.3,2
    
    0.6,0.1,0
    0.6,0.2,0
    0.6,0.3,2
\end{filecontents}

\begin{document}
    
    
\begin{tikzpicture}
    \begin{axis}
        [
        colorbar,
        colormap/viridis,
        point meta=explicit,
        point meta min=0,
        point meta max=2,
        ]
        
        \addplot[matrix plot*] 
        table [x=X,y=Y, meta=Z, col sep=comma]  {dataTest.txt};
        
        \draw[red,thick] (axis cs: 0.15,0.05) 
                      -- (axis cs: 0.15,0.15)
                      -- (axis cs: 0.45,0.15)
                      -- (axis cs: 0.45,0.25)
                      -- (axis cs: 0.8,0.25);
    \end{axis}
\end{tikzpicture}

\end{document}

谢谢你！