\addplot 图形：尽管轴的缩放比例不同，但仍保持图像的纵横比

Question

我已经使用一个复杂的程序创建了一个图，并且想要将该图的内容放入中pgfplots' axis environment。自然，\addplot graphics是实现此目的的方法。图像的纵横比（在本例中）为height > width。但是，两个轴具有不同的缩放比例x/cm >> y/cm。现在，如果没有axis equal image，pgfplots则往往会创建方形图。打开axis equal image，将使用创建图x/cm = y/cm。这两个选项都会导致绘图不遵循原始图像的纵横比。到目前为止，我发现的唯一保持纵横比的方法是手动定义和x。y unit vectors但这可能很难做到，具体取决于原始图像的大小和轴的不同缩放比例。
有没有一种简单的（最好是自动的）方法来创建一个图像图，无论轴的缩放比例如何，都能保持图像的纵横比？
下面的代码说明了这个问题。

\documentclass[10pt,varwidth=300pt]{standalone}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[english]{babel}
\usepackage{pgfplots}
\pgfplotsset{compat=1.10}
\usepackage{mwe}
\begin{document}
\includegraphics[width=100pt]{example-image-10x16}
\begin{tikzpicture}
 \begin{axis}[
  xmin=0,xmax=10,ymin=0,ymax=1,
  enlargelimits=false,
  axis equal image,
  x=1cm,y=16cm,%In this case, x and y are easy to calculate, but this will not always be the case
  ]
  \addplot graphics [xmin=0,xmax=10,ymin=0,ymax=1] {example-image-10x16};
  \end{axis}
  \node[red,anchor=south] at (current axis.north) {This is what I want};
\end{tikzpicture}
\begin{tikzpicture}
 \begin{axis}[
  xmin=0,xmax=10,ymin=0,ymax=1,
  enlargelimits=false,
  axis equal image,
  ]
  \addplot graphics [xmin=0,xmax=10,ymin=0,ymax=1] {example-image-10x16};
 \end{axis}
 \node[red,anchor=south,align=center] at (current axis.north) {This is what I get without \\ manually defining unit vectors};
\end{tikzpicture}
\begin{tikzpicture}
 \begin{axis}[
  xmin=0,xmax=10,ymin=0,ymax=1,
  enlargelimits=false,
%   axis equal image,
  ]
  \addplot graphics [xmin=0,xmax=10,ymin=0,ymax=1] {example-image-10x16};
 \end{axis}
 \node[red,anchor=south,align=center] at (current axis.north) {This is what I get without \\ manually defining unit vectors and \\ without axis equal image};
\end{tikzpicture}
\end{document}

Answer 1

这是 的功能请求pgfplots。 的当前实现\addplot graphics可以将图形挤压到轴中。但根据图形的自然大小重新配置轴仅适用于高级\addplot3 graphics[points=...]。

有趣的是，您的示例中说明的用例实际上比其他用例更简单……一定是被遗忘了。

以下是支持该宏的草稿：

\documentclass{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.10}
\begin{document}

\makeatletter
\newcommand\addplotgraphicsnatural[2][]{%
    \begingroup
    % set options in this local group (will be lost afterwards):
    \pgfqkeys{/pgfplots/plot graphics}{#1}%
    % measure the natural size of the graphics:
    \setbox0=\hbox{\includegraphics{#2}}%
    %
    % compute the required unit vector ratio:
    \pgfmathparse{\wd0/(\pgfkeysvalueof{/pgfplots/plot graphics/xmax} - \pgfkeysvalueof{/pgfplots/plot graphics/xmin})}%
    \let\xunit=\pgfmathresult
    \pgfmathparse{\ht0/(\pgfkeysvalueof{/pgfplots/plot graphics/ymax} - \pgfkeysvalueof{/pgfplots/plot graphics/ymin})}%
    \let\yunit=\pgfmathresult
    %
    % configure pgfplots to use it.
    % The \xdef expands all macros except those prefixed by '\noexpand'
    % and assigns the result to a global macro named '\marshal'.
    \xdef\marshal{%
        \noexpand\pgfplotsset{unit vector ratio={\xunit\space \yunit}}%
    }%
    \endgroup
    %
    % use our macro here:
    \marshal
    %
    \addplot graphics[#1] {#2};
}   
\makeatother

\begin{tikzpicture}
 \begin{axis}[
  axis on top,
  xmin=0,xmax=10,ymin=0,ymax=1,
  enlargelimits=false,
  ]
  \addplotgraphicsnatural[xmin=0,xmax=10,ymin=0,ymax=1]{example-image-10x16}

  \end{axis}
  \node[red,anchor=south] at (current axis.north) {This is what I want};
\end{tikzpicture}
\end{document}

新的宏从选项中读取（强制）限制并据此计算正确的单位向量比。

我的形象example-image-10x16是

\documentclass{standalone}

\usepackage{pgfplots}

\pgfplotsset{compat=1.9}
\usepgfplotslibrary{patchplots}

\begin{document}
\begin{tikzpicture}
    \begin{axis}[view={0}{90},axis equal image,hide axis]
    \addplot3[surf,shader=interp,patch type=bilinear,
        mesh/color input=explicit]
    coordinates {
        (0,0,0) [color=blue] (10,0,0) [color=green]

        (0,16,0) [color=yellow] (10,16,1) [color=red]
    };
    \end{axis}
\end{tikzpicture}
\end{document}