TikZ - 使用透明度组和不透明度在范围环境中转换准确的颜色

Question

当使用选项 [transparency group]和[opacity]并且图像在范围环境中移动时堆叠在一起，是否可以准确显示相同的图像而不改变颜色？

\documentclass{standalone}

\usepackage{pgfplots}
\usepackage{tikz}
\usetikzlibrary{positioning}

\begin{document}
\begin{tikzpicture}

\begin{scope}[transparency group, opacity=0.5]
\node[rounded corners=20mm,fill=red,minimum size=4cm] {} ;
\end{scope}

\begin{scope}[transparency group, opacity=0.5, xshift=5mm, yshift=5mm]
\node[rounded corners=20mm,fill=red,minimum size=4cm] {} ;
\end{scope}

\begin{scope}[transparency group, opacity=0.5, xshift=10mm, yshift=10mm]
\node[rounded corners=20mm,fill=red,minimum size=4cm] {} ;
\end{scope}

\end{tikzpicture}
\end{document}

Answer 1

受到@cfr 回答（+1）的鼓励，让我将我的评论扩展为一个答案：

• 一个案例，那么所有圆圈都有相同的颜色（这很容易，只需删除opacity=0.5选项）：

\documentclass[margin=3mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning}

\begin{document}
    \begin{tikzpicture}[
node distance = 5mm and 5mm, on grid,
     N/.style = {circle, minimum size=4cm, fill=red!50, 
                 node contents={}}
                        ]
\node (n1) [N];
\node (n2) [N, above right=of n1];
\node (n3) [N, above right=of n2];
\node (n4) [N, above right=of n3];
   \end{tikzpicture}
\end{document}

• 如果您喜欢看到被其他圆圈覆盖的圆圈，并看到它们的颜色，则需要为节点添加透明度，例如通过`opacity = 0.5。在这种情况下，编译结果如您所见：

为此你不需要使用transparency group：

\documentclass[margin=3mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning}

\begin{document}
    \begin{tikzpicture}[
node distance = 5mm and 5mm, on grid,
     N/.style = {circle, minimum size=4cm, fill=red, opacity=0.5,
                 node contents={}}
                        ]
\node (n1) [N];
\node (n2) [N, above right=of n1];
\node (n3) [N, above right=of n2];
\node (n4) [N, above right=of n3];
   \end{tikzpicture}
\end{document}

Answer 2

我猜你想要的结果不是你堆叠透明物体时所期望的结果，而是你将透明度应用于不规则形状时所期望的结果。

\documentclass[tikz]{standalone}
% shamelessly borrowing Zarko's code to avoid trying vainly to square circles (or circle squares?) at https://tex.stackexchange.com/questions/694688/tikz-accurate-colors-with-shifting-in-scope-environments-while-using-transpare#comment1724430_694688
\usetikzlibrary{positioning} 
\begin{document} 
\begin{tikzpicture}[ node distance = 5mm and 5mm, on grid, N/.style = {circle, minimum size=4cm, fill=red, node contents={}} ]
  \begin{scope}[transparency group,opacity=.5]
    \node (n1) [N]; \node (n2) [N, above right=of n1]; \node (n3) [N, above right=of n2]; 
  \end{scope}
\end{tikzpicture} 
\end{document}