在 Beamer 中忘记暂停前的内容

Question

我正在使用 beamer

我在图像上绘制一些图形，这些图形应该按顺序出现在图像上。

    \documentclass{beamer}
    \usepackage{tikz}

    \begin{document}

\begin{frame}
        \begin{tikzpicture}

            \node[anchor=south west,inner sep=0] (image) at (0,0) {\includegraphics[width=0.9\textwidth]{1.png}};
            \begin{scope}[x={(image.south east)},y={(image.north west)}]
                \draw[help lines,xstep=.1,ystep=.1] (0,0) grid (1,1);
                \foreach \x in {0,1,...,9} { \node [anchor=north] at (\x/10,0) {0.\x}; }
                \foreach \y in {0,1,...,9} { \node [anchor=east] at (0,\y/10) {0.\y}; }
                \draw[red,ultra thick,rounded corners] (0.2,0.84) rectangle (0.1,0.95); \pause
                \draw[red,ultra thick,rounded corners] (0.52,0.7) rectangle (0.85,0.36); \pause
                \draw[red,ultra thick,rounded corners] (0.09,0.84) rectangle (0.294,0.16); \pause
                \draw[red,ultra thick,rounded corners] (0.12,0.15) rectangle (0.294,0.06); \pause
                \draw[red,ultra thick,rounded corners] (0.36,0.7) rectangle (0.48,0.31); \pause
                \draw[red,ultra thick,rounded corners] (0.04,0.94) rectangle (0.85,0.2);

            \end{scope}
        \end{tikzpicture}

\end{frame}
    \end{document}

问题：图像上出现新图形后，我希望旧图形淡出。

这该怎么做？非常感谢您的帮助。

Answer 1

如果您想要动画淡入淡出，beamer可以通过创建多个幻灯片来实现，这些幻灯片上的对象颜色略有不同，并快速连续显示这些对象（就像翻书一样，仅在演示模式下有效）。这可能会生成包含许多页面的 pdf，我不确定您是否想要。此外，淡入不可见可能会有问题。当前版本的 beamer（3.36）不支持“真正的”透明度，因此通过将对象的颜色与框架背景颜色混合来伪造它。这会在您的情况下导致问题，因为您正在图形上绘制形状。在尝试使对象透明时，beamer实际上会使它们变为白色（以匹配背景），而不管图形颜色如何。

如果您希望对象在绘制之后完全消失，则可以使用\visible指定每个对象应在哪些幻灯片上可见。

\documentclass{beamer}
\usepackage{tikz}
\begin{document}
\begin{frame}
\begin{tikzpicture}
    \node[anchor=south west,inner sep=0] (image) at (0,0) {\includegraphics[width=0.9\textwidth]{example-image}};
    \begin{scope}[x={(image.south east)},y={(image.north west)}]
        \draw[help lines,xstep=.1,ystep=.1] (0,0) grid (1,1);
        \foreach \x in {0,1,...,9} { \node [anchor=north] at (\x/10,0) {0.\x}; }
        \foreach \y in {0,1,...,9} { \node [anchor=east] at (0,\y/10) {0.\y}; }
        \visible<1>{\draw[red,ultra thick,rounded corners] (0.2,0.84) rectangle (0.1,0.95);}
        \visible<2>{\draw[red,ultra thick,rounded corners] (0.52,0.7) rectangle (0.85,0.36);}
        \visible<3>{\draw[red,ultra thick,rounded corners] (0.09,0.84) rectangle (0.294,0.16);}
        \visible<4>{\draw[red,ultra thick,rounded corners] (0.12,0.15) rectangle (0.294,0.06);}
        \visible<5>{\draw[red,ultra thick,rounded corners] (0.36,0.7) rectangle (0.48,0.31);}
        \visible<6>{\draw[red,ultra thick,rounded corners] (0.04,0.94) rectangle (0.85,0.2);}
    \end{scope}
\end{tikzpicture}
\end{frame}
\end{document}

或者，您可以使用\temporal来定义给定幻灯片之前、之上和之后的外观。在下文中，\colorize定义为在给定幻灯片之前不可见，在给定幻灯片上为红色，此后为 35% 黑色。

\documentclass{beamer}
\usepackage{tikz}
\def\colorize<#1>{%
    \temporal<#1>{\invisible<-#1>}{\color{red}}{\color{black!35}}}
\begin{document}
\begin{frame}
\begin{tikzpicture}
    \node[anchor=south west,inner sep=0] (image) at (0,0) {\includegraphics[width=0.9\textwidth]{example-image}};
    \begin{scope}[x={(image.south east)},y={(image.north west)}]
        \draw[help lines,xstep=.1,ystep=.1] (0,0) grid (1,1);
        \foreach \x in {0,1,...,9} { \node [anchor=north] at (\x/10,0) {0.\x}; }
        \foreach \y in {0,1,...,9} { \node [anchor=east] at (0,\y/10) {0.\y}; }

        \colorize<1>{\draw[ultra thick,rounded corners] (0.2,0.84) rectangle (0.1,0.95);}
        \colorize<2>{\draw[ultra thick,rounded corners] (0.52,0.7) rectangle (0.85,0.36);}
        \colorize<3>{\draw[ultra thick,rounded corners] (0.09,0.84) rectangle (0.294,0.16);}
        \colorize<4>{\draw[ultra thick,rounded corners] (0.12,0.15) rectangle (0.294,0.06);}
        \colorize<5>{\draw[ultra thick,rounded corners] (0.36,0.7) rectangle (0.48,0.31);}
        \colorize<6>{\draw[ultra thick,rounded corners] (0.04,0.94) rectangle (0.85,0.2);}
    \end{scope}
\end{tikzpicture}
\end{frame}
\end{document}