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diff --git a/graphics/pgf/base/doc/pgfmanual-en-library-spy.tex b/graphics/pgf/base/doc/pgfmanual-en-library-spy.tex new file mode 100644 index 0000000000..a85ff6a515 --- /dev/null +++ b/graphics/pgf/base/doc/pgfmanual-en-library-spy.tex @@ -0,0 +1,463 @@ +% Copyright 2019 by Till Tantau +% +% This file may be distributed and/or modified +% +% 1. under the LaTeX Project Public License and/or +% 2. under the GNU Free Documentation License. +% +% See the file doc/generic/pgf/licenses/LICENSE for more details. + + +\section{Spy Library: Magnifying Parts of Pictures} +\label{section-library-spy} + +\begin{tikzlibrary}{spy} + The package defines options for creating pictures in which some part of the + picture is repeated in another area in a magnified way (as if you were + looking through a spyglass, hence the name). +\end{tikzlibrary} + + +\subsection{Magnifying a Part of a Picture} + +The idea behind the |spy| library is to make it easy to create high-density +pictures in which some important parts are repeated somewhere, but magnified as +if you were looking through a spyglass: +% +\begin{codeexample}[preamble={\usetikzlibrary{decorations.fractals,spy}}] +\begin{tikzpicture} + [spy using outlines={circle, magnification=4, size=2cm, connect spies}] + + \draw [help lines] (0,0) grid (3,2); + + \draw [decoration=Koch curve type 1] + decorate { decorate{ decorate{ decorate{ (0,0) -- (2,0) }}}}; + + \spy [red] on (1.6,0.3) + in node [left] at (3.5,-1.25); + + \spy [blue, size=1cm] on (1,1) + in node [right] at (0,-1.25); +\end{tikzpicture} +\end{codeexample} + +\begin{codeexample}[preamble={\usetikzlibrary{decorations.fractals,spy}}] +\begin{tikzpicture}[spy using overlays={size=12mm}] + \draw [decoration=Koch snowflake] + decorate { decorate{ decorate{ decorate{ (0,0) -- (2,0) }}}}; + + \spy [green,magnification=3] on (0.6,0.1) in node at (-0.3,-1); + \spy [blue,magnification=5] on (1,0.5) in node at (1,-1); + \spy [red,magnification=10] on (1.6,0.1) in node at (2.3,-1); +\end{tikzpicture} +\end{codeexample} + +Note that this magnification uses what is called a \emph{canvas transformation} +in this manual: Everything is magnified, including line width and text. + +In order for ``spying'' to work, the picture obviously has to be drawn several +times: Once at its normal size and then again for each ``magnifying glass''. +Several keys and commands work in concert to make this possible: +% +\begin{itemize} + \item You need to make \tikzname\ aware of the fact that a picture (or just + a scope) is to be magnified. This is done by adding the special key + |spy scope| to a |{scope}| or |{tikzpicture}| (which is also just a + scope). Some special keys like |spy using outlines| implicitly set the + |spy scope|. + \item Inside this scope you may then use the command |\spy|, which is only + available inside such scopes (so there is no danger of you + inadvertently using this command outside such a scope). This command + has a special syntax and will (at some point) create two nodes: One + node that shows the magnified picture (called the \emph{spy-in node}) + and another node showing which part of the original picture is + magnified (called the \emph{spy-on} node). The spy-in node is, indeed, + a normal node, so it can have any shape or border that you like and you + can apply all of \tikzname's advanced features to it. The only + difference compared to a normal node is that instead of some ``text'' + it contains a magnified version of the picture, clipped to the size of + the node. + + The |\spy| command does not create the nodes immediately. Rather, the + creation of these nodes is postponed till the end of the |spy scope| in + which the |\spy| command is used. This is necessary since in order to + repeat the whole scope inside the node containing the magnified + version, the whole picture needs to be available when this node is + created. +\end{itemize} + +A basic question any library for ``magnifying things'' has to address is how +you specify which part of the picture is to be magnified (the spy-on node) and +where this magnified part is to be shown (the spy-in node). There are two +possible ways: +% +\begin{enumerate} + \item You specify the size and position of the spy-on node. Then the size + of the spy-in node is determined by the size of the spy-on node and the + magnification factor -- you can still decide where the spy-in node + should be placed, but not its size. + \item Alternatively, you specify the size and position of the spy-in node. + Then, similarly to the first case, the size of the spy-on node is + determined implicitly and you can only decide where the spy-on node + should be placed, but not its size. +\end{enumerate} + +The |spy| library uses the second method: You specify the size and position of +the spy-in nodes, the sizes of the spy-on nodes are then computed +automatically. + + +\subsection{Spy Scopes} + +\begin{key}{/tikz/spy scope=\meta{options} (default \normalfont empty)} + This option may be used with a |{scope}| or any environment that creates + such a scope internally (like |{tikzpicture}|). It has the following + effects: + % + \begin{itemize} + \item It resets a number of graphic state parameters, including the + color, line style, and others. This is necessary for technical + reasons. + \item It tells \tikzname\ that the content of the scope should be saved + internally in a special box. + \item It defines the command |\spy| so that it can be used inside the + scope. + \item At the end of the scope, the nodes belonging to the |\spy| + commands used inside the scope are created. + \item The \meta{options} are saved in an internal style. Each time + |\spy| is used, these \meta{options} will be used. + \item Three keys are defined that provide useful shortcuts: + % + \begin{key}{/tikz/size=\meta{dimension}} + Inside a |spy scope|, this is a shortcut for |minimum size|. + \end{key} + % + \begin{key}{/tikz/height=\meta{dimension}} + Inside a |spy scope|, this is a shortcut for |minimum height|. + \end{key} + % + \begin{key}{/tikz/width=\meta{dimension}} + Inside a |spy scope|, this is a shortcut for |minimum width|. + \end{key} + \end{itemize} + % + It is permissible to nest |spy scopes|. In this case, all |\spy| commands + inside the inner |spy scope| only have an effect on material inside the + scope, whereas |\spy| commands outside the inner |spy scope| but inside the + outer |spy scope| allow you to ``spy on the spy''. + % +\begin{codeexample}[preamble={\usetikzlibrary{decorations.fractals,spy}}] +\begin{tikzpicture} + [spy using outlines={rectangle, red, magnification=5, + size=1.5cm, connect spies}] + + \begin{scope} + [spy using outlines={circle, blue, + magnification=3, size=1.5cm, connect spies}] + \draw [help lines] (0,0) grid (3,2); + + \draw [decoration=Koch curve type 1] + decorate{ decorate{ decorate{ (0,0) -- (2,0) }}}; + + \spy on (1.6,0.3) in node (zoom) [left] at (3.5,-1.25); + \end{scope} + + \spy on (zoom.north west) in node [right] at (0,-1.25); +\end{tikzpicture} +\end{codeexample} + % +\end{key} + + +\subsection{The Spy Command} + +\begin{command}{\spy \opt{\oarg{options}} |on| \meta{coordinate} \texttt{in node} \meta{node options}|;|} + This command can only be used inside a |spy scope|. Let us start with the + syntax: + % + \begin{itemize} + \item The |\spy| command is not a special case of |\path|. Rather, it + has a small parser of its own. + \item Following the optional \meta{options}, you must write |on|, + followed by a coordinate. This coordinate will be the center of the + area that is to be magnified. + \item Following the \meta{coordinate}, you must write |in node| + followed by some \meta{node options}. The syntax for these options + is the same as for a normal |node| path command, such as |[left]| + or |(foo) [red] at (bar)|. \emph{However}, \meta{node options} are + \emph{not} followed by a curly brace. Rather, the \meta{node + options} must directly be followed by a semicolon. + \end{itemize} + % + The effect of this command is the following: The \meta{options}, + \meta{coordinate}, and \meta{node options} are stored internally till the + end of the current |spy scope|. This means that, in particular, you can + reference any node inside the |spy scope|, even if it is not yet defined + when the |\spy| command is given. At the end of the current |spy scope|, + two nodes are created, called the \emph{spy-in node} and the \emph{spy-on + node}. + % + \begin{itemize} + \item The \emph{spy-in node} is the node that contains a magnified part + of the picture (the node \emph{in} which we see on what we spy). + This node is, indeed, a normal \tikzname\ node, so you can use all + standard options to style this node. In particular, you can specify + a shape or a border color or a drop shadow or whatever. The only + thing that is special about this node is that instead of containing + some normal text, its ``text'' is the magnified picture. + + To be precise, the picture of the |spy scope| is scaled by a + certain factor, specified by the |lens| or |magnification| options + discussed below, and is shifted in such a way that the + \meta{coordinate} lies at the center of the spy-on node. + \item The \emph{spy-on node} is a node that is centered on the + \meta{coordinate} and whose size reflects exactly the area shown + inside the spy-in node (the node containing \emph{on} what we spy). + \end{itemize} + + Let us now go over what happens in detail when the two nodes are + created: + % + \begin{enumerate} + \item A scope is started. Two sets of options are used with this scope: + First, the options passed to the enclosing |spy scope| and then the + \meta{options} (which will, thus, overrule the options of the + |spy scope|). + \item Then, the spy-on node is created. However, we will first discuss + the spy-in node. + \item The spy-in node is created after the spy-on node (and, hence, + will cover the spy-on node in case they overlap). When this node is + created, the \meta{node options} are used in addition to the effect + caused by the \meta{options} and the options of the |{spy scope}|. + Additionally, the following style is used: + % + \begin{stylekey}{/tikz/every spy in node} + This style is used with every spy-in node. + \end{stylekey} + % + The position of the node (the |at| option) is set to the + \meta{coordinate} by default, so that it will cover the + to-be-magnified area. You can change this by providing the |at| + option yourself: + % +\begin{codeexample}[preamble={\usetikzlibrary{decorations.fractals,spy}}] +\begin{tikzpicture} + [spy using outlines={circle, magnification=3, size=1cm}] + + \draw [decoration=Koch curve type 1] + decorate{ decorate{ decorate{ (0,0) -- (2,0) }}}; + + \spy [red] on (1.6,0.3) in node; + \spy [blue] on (1,1) in node at (1,-1); +\end{tikzpicture} +\end{codeexample} + % + No ``text'' can be specified for the node. Rather, the ``text'' + shown inside this node is the picture of the current |spy scope|, + but canvas-transformed according to the following key: + % + \begin{key}{/tikz/lens=\meta{options}} + The \meta{options} should contain transformation commands like + |scale| or |rotate|. These transformations are applied to the + picture when it is shown inside the spy-on node. + \end{key} + % + Since the most common transformation is undoubtedly a simple + scaling, there is a special style for this: + % + \begin{key}{/tikz/magnification=\meta{number}} + This has the same effect as saying + |lens={scale=|\meta{number}|}|. + \end{key} + % + Now, usually the size of a node is determined in such a way that it + ``fits'' around the text of the node. For a spy-on node this is not + a good approach since the ``text'' of this node would contain ``the + whole picture''. Because of this, \tikzname\ acts as if the + ``text'' of the node has zero size. You must then use keys like + |minimum size| to cause the node to have a certain size. Note that + the key |size| is an abbreviation for |minimum size| inside a spy + scope. + + You can name the spy-on node in the usual ways. Additionally, the + node is (also) always named |tikzspyinnode|. Following the spy + scope, you can use this node like any other node: + % +\begin{codeexample}[preamble={\usetikzlibrary{decorations.fractals,spy}}] +\begin{tikzpicture} + \begin{scope} + [spy using outlines={circle, magnification=3, size=2cm, connect spies}] + + \draw [decoration=Koch curve type 1] + decorate{ decorate{ decorate{ (0,0) -- (2,0) }}}; + + \spy [red] on (1.6,0.3) in node (a) [left] at (3.5,-1.25); + + \spy [blue, size=1cm] on (1,1) in node (b) [right] at (0,-1.25); + \end{scope} + \draw [ultra thick, green!50!black] (b) -- (a.north west); +\end{tikzpicture} +\end{codeexample} + % + \item Once both nodes have been created, the current value of the + following key is used to connect them: + % + \begin{key}{/tikz/spy connection path=\meta{code} (initially \normalfont empty)} + The \meta{code} is executed after the spy-on and spy-in nodes + have just been created. Inside this \meta{code}, the two nodes + can be accessed as |tikzspyinnode| and |tikzspyonnode|. For + example, the key |connect spies| sets this command to + % +\begin{codeexample}[code only] +\draw[thin] (tikzspyonnode) -- (tikzspyinnode); +\end{codeexample} + \end{key} + \end{enumerate} + % + Returning to the creation of the spy-in node: This node is centered on + \meta{coordinate} (more precisely, its anchor is set to |center| and the + |at| option is set to \meta{coordinate}). Its size and shape are initially + determined in the same way as the size and shape of the spy-on node + (unless, of course, you explicitly provide a different shape for, say, the + spy-on node locally, which is not really a good idea). Then, additionally, + the \emph{inverted} transformation done by the |lens| option is applied, + resulting in a node whose size and shape exactly corresponds to the area in + the picture that is shown in the spy-on node. + % +\begin{codeexample}[preamble={\usetikzlibrary{decorations.fractals,spy}}] +\begin{tikzpicture} + [spy using outlines={lens={scale=3,rotate=20}, size=2cm, connect spies}] + + \draw [decoration=Koch curve type 1] + decorate{ decorate{ decorate{ (0,0) -- (2,0) }}}; + + \spy [red] on (1.6,0.3) in node at (2.5,-1.25); +\end{tikzpicture} +\end{codeexample} + + Like for the spy-in node, a style can be used to format the spy-on node: + % + \begin{stylekey}{/tikz/every spy on node} + This style is used with every spy-on node. + \end{stylekey} + % + The spy-on node is named |tikzspyonnode| (but, as always, this node is only + available after the spy scope). If you have multiple spy-on nodes and you + would like to access all of them, you need to use the |name| key inside the + |every spy on node| style. + + The |inner sep| and |outer sep| of both spy-in and spy-on nodes are set to + |0pt|. +\end{command} + + +\subsection{Predefined Spy Styles} + +There are some predefined styles that make using the |spy| library easier. The +following two styles can be used instead of |spy scope|, they pass their +\meta{options} directly to |spy scope|. They additionally set up the graphic +styles to be used for the spy-in nodes and the spy-on nodes in some special +way. + +\begin{key}{/tikz/spy using outlines=\meta{options} (default \normalfont empty)} + This key creates a |spy scope| in which the spy-in node is drawn, but not + filled, using a thick line; and the spy-on node is drawn, but not filled, + using a very thin line. + % +\begin{codeexample}[preamble={\usetikzlibrary{decorations.fractals,spy}}] +\begin{tikzpicture} + [spy using outlines={circle, magnification=3, size=1cm, connect spies}] + + \draw [decoration=Koch curve type 1] + decorate{ decorate{ decorate{ (0,0) -- (2,0) }}}; + + \spy [red] on (1.6,0.3) in node at (3,1); +\end{tikzpicture} +\end{codeexample} + % +\end{key} + +\begin{key}{/tikz/spy using overlays=\meta{options} (default \normalfont empty)} + This key creates a |spy scope| in which both the spy-in and spy-on nodes + are filled, but with the fill opacity set to 20\%. + % +\begin{codeexample}[preamble={\usetikzlibrary{decorations.fractals,spy}}] +\begin{tikzpicture} + [spy using overlays={circle, magnification=3, size=1cm, connect spies}] + + \draw [decoration=Koch curve type 1] + decorate{ decorate{ decorate{ (0,0) -- (2,0) }}}; + + \spy [green] on (1.6,0.3) in node at (3,1); +\end{tikzpicture} +\end{codeexample} + % +\end{key} + +The following style is useful for connecting the spy-in and the spy-on nodes: + +\begin{key}{/tikz/connect spies} + Causes the spy-in and the spy-on nodes to be connected by a thin line. + % +\begin{codeexample}[preamble={\usetikzlibrary{decorations.fractals,spy}}] +\begin{tikzpicture} + [spy using overlays={circle, magnification=3, size=1cm}] + + \draw [decoration=Koch curve type 2] + decorate{ decorate{ decorate{ (0,0) -- (2,0) }}}; + + \spy [green] on (1.6,0.1) in node at (3,1); + \spy [red,connect spies] on (0.5,0.4) in node at (1,1.5); +\end{tikzpicture} +\end{codeexample} + % +\end{key} + + +\subsection{Examples} + +Usually, the spy-in node and the spy-on node should have the same shape. +However, you might also wish to use the |circle| shape for the spy-on node and +the |magnifying glass| shape for the spy-in node: +% +\begin{codeexample}[preamble={\usetikzlibrary{decorations.fractals,shadows,shapes.symbols,spy}}] +\tikzset{spy using mag glass/.style={ + spy scope={ + every spy on node/.style={ + circle, + fill, fill opacity=0.2, text opacity=1}, + every spy in node/.style={ + magnifying glass, circular drop shadow, + fill=white, draw, ultra thick, cap=round}, + #1 + }}} +\begin{tikzpicture}[spy using mag glass={magnification=3, size=1cm}] + \draw [decoration=Koch curve type 2] + decorate{ decorate{ decorate{ (0,0) -- (2,0) }}}; + + \spy [green!50!black] on (1.6,0.1) in node at (2.5,-0.5); +\end{tikzpicture} +\end{codeexample} + +With the magnifying glass, you can also put it ``on top'' of the picture +itself: +% +\begin{codeexample}[preamble={\usetikzlibrary{decorations.fractals,shadows,shapes.symbols,spy}}] +\begin{tikzpicture} + [spy scope={magnification=4, size=1cm}, + every spy in node/.style={ + magnifying glass, circular drop shadow, + fill=white, draw, ultra thick, cap=round}] + + \draw [decoration=Koch curve type 2] + decorate{ decorate{ decorate{ (0,0) -- (2,0) }}}; + + \spy on (1.6,0.1) in node; +\end{tikzpicture} +\end{codeexample} + + +%%% Local Variables: +%%% mode: latex +%%% TeX-master: "pgfmanual-pdftex-version" +%%% End: |