PGF/TikZ Manual

# The TikZ and PGF Packages Manual for version 3.1.10

## Libraries

#### 50Decoration Library

##### 50.1Overview and Common Options¶

The decoration libraries define a number of (more or less useful) decorations that can be applied to paths. The usage of decorations is not covered in the present section, please consult Sections 24, which explains how decorations are used in TikZ, and 103, which explains how new decorations can be defined.

The decorations are influenced by a number of parameters that can be set using the decoration option. These parameters are typically shared between different decorations. In the following, the general options are documented (they are defined directly in the decoration module), special-purpose keys are documented with the decoration that uses it.

Since you are encouraged to use these keys to make your own decorations configurable, it is indicated for each key where the value is stored (so that you can access it). Note that some values are stored in dimension registers while others are stored in macros.

• /pgf/decoration/amplitude=dimension (no default, initially 2.5pt)

• This key determines the “desired height” (or amplitude) of decorations for which this makes sense. For instance, the initial value of 2.5pt means that deforming decorations should deform a path by up to 2.5pt away from the original path.

This key sets the -dimension \pgfdecorationsegmentamplitude.

• /pgf/decoration/meta-amplitude=dimension (no default, initially 2.5pt)

• This key determines the amplitude for a meta-decoration.

The key sets the -macro (!) \pgfmetadecorationsegmentamplitude.

• /pgf/decoration/segment length=dimension (no default, initially 10pt)

• Many decorations are made up of small segments. This key determines the desired length of such segments.

This key sets the -dimension \pgfdecorationsegmentlength.

• /pgf/decoration/meta-segment length=dimension (no default, initially 1cm)

• This determined the length of the meta-segments from which a meta-decoration is made up.

This key sets the -macro (!) \pgfmetadecorationsegmentlength.

• /pgf/decoration/angle=degree (no default, initially 45)

• The way some decorations look like depends on a configurable angle. For instance, a wave decoration consists of arcs and the opening angle of these arcs is given by the angle.

This key sets the -macro \pgfdecorationsegmentangle.

• /pgf/decoration/aspect=factor (no default, initially 0.5)

• For some decorations there is a natural aspect ratio. For instance, for a brace decoration the aspect ratio determines where the brace point will be.

This key sets the -macro \pgfdecorationsegmentaspect.

• /pgf/decoration/start radius=dimension (no default, initially 2.5pt)

• For some decorations there is a natural start radius (of some circle, presumably).

This key stores the value directly inside the key.

• /pgf/decoration/end radius=dimension (no default, initially 2.5pt)

• For some decorations there is a natural end radius (of some circle, presumably).

This key stores the value directly inside the key.

• Sets the start and end radius simultaneously.

• /pgf/decoration/path has corners=boolean (no default, initially false)

• This is a hint to the decoration code as to whether the path has corners or not. If a path has a sharp corner, setting this option to true may result in better rendering of the decoration because the joins of input segments are approached “more carefully” than when this key is set to false. However, if the path is, say, a smooth circle, setting this key to true will usually look worse. Most decorations ignore this key, anyway. Internally, it sets the -if \ifpgfdecoratepathhascorners.

##### 50.2Handling “Dimension too large” errors¶

In case you should run into a “Dimension too large error” when using the decorations libraries, there is a pretty high chance that you can resolve this by using the fpu library in combination with /pgf/fpu/install only={reciprocal}. Please note that this key should only be applied locally to avoid other errors (see also at the definition of this key in section 56.2).

##### 50.3Path Morphing Decorations¶
• TikZ Library decorations.pathmorphing

• \usepgflibrary{decorations.pathmorphing} % and plain and pure pgf
\usepgflibrary[decorations.pathmorphing] % Cont and pure pgf
\usetikzlibrary{decorations.pathmorphing} % and plain when using TikZ
\usetikzlibrary[decorations.pathmorphing] % Cont when using TikZ

A path morphing decoration “morphs” or “deforms” the to-be-decorated path. This means that what used to be a straight line might afterwards be a snaking curve and have bumps. However, a line is still a line and path deforming decorations do not change the number of subpaths. For instance, if the path used to consist of two circles and an open arc, the path will, after the decoration process, still consist of two closed subpaths and one open subpath.

###### 50.3.1Decorations Producing Straight Line Paths¶

The following deformations use only straight lines in order to morph the paths.

• Decoration lineto

• This decoration replaces the path by straight lines. For each curve, the path simply goes directly from the start point to the end point. In the following example, the arc actually consist of two subcurves.

This decoration is actually always defined when the decoration module is loaded, but it is documented here for consistency.

• Decoration straight zigzag

• This (meta-)decoration decorates the path by alternating between curveto and zigzag decorations. It always finishes with the curveto decoration. The following parameters influence the decoration:

• amplitude determines how much the zigzag line raises above and falls below a straight line to the target point.

• segment length determines the length of a complete “up-down” cycle.

• meta-segment length determines the length of the curveto and the zigzag decorations.

• Decoration random steps

• This decoration consists of straight line segments. The line segments head towards the target, but each step is randomly shifted a little bit. The following parameters influence the decorations:

• segment length determines the basic length of each step.

• amplitude The end of each step is perturbed both in $$x$$- and in $$y$$-direction by two values drawn uniformly from the interval $$[-d,d]$$, where $$d$$ is the value of amplitude.

• Decoration saw

• This decoration looks like the blade of a saw. The following parameters influence the decoration:

• amplitude determines how much each spike raises above the straight line.

• segment length determines the length each spike.

• Decoration zigzag

• This decoration looks like a zigzag line. The following parameters influence the decoration:

• amplitude determines how much the zigzag line raises above and falls below a straight line to the target point.

• segment length determines the length of a complete “up-down” cycle.

###### 50.3.2Decorations Producing Curved Line Paths¶
• Decoration bent

• This decoration adds a slightly bent line from the start to the target. The amplitude of the bend is given amplitude (an amplitude of zero gives a straight line).

• amplitude determines the amplitude of the bend.

• aspect determines how tight the bend is. A good value is around 0.3.

Note that this decoration makes only little sense for curves. You should apply it only to straight lines.

• Decoration bumps

• This decoration replaces the path by little half ellipses. The following parameters influence it.

• amplitude determines the height of the half ellipse.

• segment length determines the width of the half ellipse.

• Decoration coil

• This decoration replaces the path by a coiled line. To understand how this works, imagine a three-dimensional spring. The spring’s axis points along the path toward the target. Then, we “view” the spring from a certain angle. If we look “straight from the side” we will see a perfect sine curve, if we look “more from the front” we will see a coil. The following parameters influence the decoration:

• amplitude determines how much the coil rises above the path and falls below it. Thus, this is the radius of the coil.

• segment length determines the distance between two consecutive “curls”. Thus, when the spring is see “from the side” this will be the wave length of the sine curve.

• aspect determines the “viewing direction”. A value of 0 means “looking from the side” and a value of 0.5, which is the default, means “look more from the front”.

• Decoration curveto

• This decoration simply yields a line following the original path. This means that (ideally) it does not change the path and follows any curves in the path (hence the name). In reality, due to the internals of how decorations are implemented, this decoration actually replaces the path by numerous small straight lines.

This decoration is mostly useful in conjunction with meta-decorations. It is also actually defined in the decoration module and is always available.

• Decoration snake

• This decoration replaces the path by a line that looks like a snake seen from above. More precisely, the snake is a sine wave with a “softened” start and ending. The following parameters influence the snake:

• amplitude determines the sine wave’s amplitude.

• segment length determines the sine wave’s wavelength.

##### 50.4Path Replacing Decorations¶
• TikZ Library decorations.pathreplacing

• \usepgflibrary{decorations.pathreplacing} % and plain and pure pgf
\usepgflibrary[decorations.pathreplacing] % Cont and pure pgf
\usetikzlibrary{decorations.pathreplacing} % and plain when using TikZ
\usetikzlibrary[decorations.pathreplacing] % Cont when using TikZ

This library defines decorations that replace the to-be-decorated path by another path. Unlike morphing decorations, the replaced path might be quite different, for instance a straight line might be replaced by a set of circles. Note that filling a path that has been replaced using one of the decorations in this library typically does not fill the original area but, rather, the smaller area of the newly-created path segments.

• Decoration border

• This decoration adds straight lines to the path that are at a specific angle to the line toward the target. The idea is to add these little lines to indicate the “border” of an area. The following parameters influence the decoration:

• segment length determines the distance between consecutive ticks.

• amplitude determines the length of the ticks.

• angle determines the angle between the ticks and the line of the path.

• Decoration brace

• This decoration replaces a straight line path by a long brace. The left and right end of the brace will be exactly on the start and endpoint of the decoration. The decoration really only makes sense for paths that are a straight line.

• amplitude determines how much the brace rises above the path.

• aspect determines the fraction of the total length where the “middle part” of the brace will be.

• Decoration expanding waves

• This decoration adds arcs to the path that get bigger along the line towards the target. The following parameters influence the decoration:

• segment length determines the distance between consecutive arcs.

• angle determines the opening angle below and above the path. Thus, the total opening angle is twice this angle.

• Decoration moveto

• This decoration simply jumps to the end of the path using a move-to path operation. It is mainly useful as pre=moveto or post=moveto decorations.

This decoration is actually always defined when the decoration module is loaded, but it is documented here for consistency.

• Decoration ticks

• This decoration replaces the path by straight lines that are orthogonal to the path. The following parameters influence the decoration:

• segment length determines the distance between consecutive ticks.

• amplitude determines half the length of the ticks.

• Decoration waves

• This decoration replaces the path by arcs that have a constant size. The following parameters influence the decoration:

• segment length determines the distance between consecutive arcs.

• angle determines the opening angle below and above the path. Thus, the total opening angle is twice this angle.

• Decoration show path construction

• This decoration allows “something different” to be done for each type of input segment (i.e., moveto, lineto, curveto or closepath). Typically, each segment will be replaced with another path, but this need not necessarily be the case.

The following keys can be used to specify the code to execute for each type of input segment.

• /pgf/decoration/moveto code=code (no default, initially {})

• Set the code to be executed for every moveto input segment. It is important to remember that the transformations applied by the decoration automaton are turned off when code is executed.

• /pgf/decoration/lineto code=code (no default, initially {})

• Set the code to be executed for every lineto input segment.

• /pgf/decoration/curveto code=code (no default, initially {})

• Set the code to be executed for every curveto input segment.

• /pgf/decoration/closepath code=code (no default, initially {})

• Set the code to be executed for every closepath input segment.

Within code the first and last points on the current input segment can be accessed using \pgfpointdecoratedinputsegmentfirst and \pgfpointdecoratedinputsegmentlast. For curves, the control (support) points can be accessed using \pgfpointdecoratedinputsegmentsupporta and \pgfpointdecoratedinputsegmentsupportb.

In TikZ, you can use the following macros inside a TikZ coordinate.

• \tikzinputsegmentfirst

• The first point on the current input segment path.

• \tikzinputsegmentlast

• The last point on the current input segment path.

• \tikzinputsegmentsupporta

• The first support on the curveto input segment path.

• \tikzinputsegmentsupportb

• The second support on the curveto input segment path.

##### 50.5Marking Decorations¶
###### 50.5.1Overview¶

A marking on a path is any kind of graphic that is placed on a specific position on a path. Markings are useful in rather diverse situations: you can use them to, say, place little “footsteps” along a path as if someone where walking along the path; to place arrow tips on the middle of a path to indicate the “direction” in which something is flowing; or you can use them to place informative information at certain positions of a path.

For historical reasons there are three different libraries for placing marks on a path. They differ in what kind of markings can be added to a path. We start with the most general and most useful of these libraries.

##### 50.6Arbitrary Markings¶
• TikZ Library decorations.markings

• \usepgflibrary{decorations.markings} % and plain and pure pgf
\usepgflibrary[decorations.markings] % Cont and pure pgf
\usetikzlibrary{decorations.markings} % and plain when using TikZ
\usetikzlibrary[decorations.markings] % Cont when using TikZ

Markings are arbitrary “marks” that can be put on a path. Marks can be arrow tips or nodes or even whole pictures.

• Decoration markings

• A marking can be thought of a “little picture” or more precisely of “some scope contents” that is placed “on” a path at a certain position. Suppose the marking should be a simple cross. We can produce this with the following code:

If we use this code as a marking at position 2cm on a path, then the following happens: pgf determines the position on the path that is 2cm along the path. Then is translates the coordinate system to this position and rotates it such that the positive $$x$$-axis is tangent to the path. Then a protective scope is created, inside which the above code is executed – resulting in a little cross on the path.

The markings decoration allows you to place one or more such markings on a path. The decoration destroys the input path (except in certain cases, detailed later), which means that it uses the path for determining positions on the path, but after the decoration is done this path is gone. You typically need to use a postaction to add markings.

We can also add the cross repeatedly:

The mark decoration option is used to specify a marking. It comes in two versions:

• /pgf/decoration/mark=at position pos with code(no default)

• The options specifies that when a marking decoration is applied, there should be a marking at position pos on the path whose code is given by code.

The pos can have four different forms:

• 1. It can be a non-negative dimension like 0pt or 2cm or 5cm/2. In this case, it refers to the position along the path that is this far displaced from the start.

• 2. It can be a negative dimension like -1cm-2pt or -1sp. In this case, the position is taken from the end of the path. Thus, -1cm is the position that is $$-1$$cm displaced from the end of the path.

• 3. It can be a dimensionless non-negative number like 1/2 or 0.333+2*0.1. In this case, the pos is interpreted as a factor of the total path length. Thus, a pos or 0.5 refers to the middle of the path, 0.1 is near the start, and so on.

• 4. It can be a dimensionless negative number like -0.1. Then, again, the fraction of the path length counts “from the end”.

The pos determines a position on the path. When the marking is applied, the (high level) coordinate system will have been transformed so that the origin lies at this position and the positive $$x$$-axis points along the path. For this coordinate system, the code is executed. It can contain all sorts of graphic drawing commands, including (even named) nodes.

If the position lies past the end of the path (for instance if pos is set to 1.2), the marking will not be drawn.

It is possible to give the mark option several times, which causes several markings to be applied. In this case, however, it is necessary that the positions on the path are in increasing order. That is, it is not allowed (and will result in chaos) to have a marking that lies earlier on the path to follow a marking that is later on the path.

Here is an example that shows how markings can be used to place text on plots:

When the code is being executed, two special keys will have been set up, whose value may be of interest:

• /pgf/decoration/mark info/sequence number(no value)

• This key can only be read. Its value (which can be obtained using the \pgfkeysvalueof command) is a “sequence number” of the mark. The first mark that is added to a path has number 1, the second number 2, and so on. This key is mainly useful in conjunction with repeated markings (see below).

• /pgf/decoration/mark info/distance from start(no value)

• This key can only be read. Its value is the distance of the marking from the start of the path in points. For instance, if the path length is 100pt and the marking is in the middle of the path, the value of this key would be 50.0pt.

A second way to use the mark key is the following:

• /pgf/decoration/mark=between positions start pos and end pos step stepping with code(no default)

• This works similarly to the at position version of this option, only multiple marks are placed, starting at start pos and then spaced apart by stepping. The start pos, the end pos, and also the stepping may all be specified in the same way as for the at position version, that is, either using units or no units and also using positive or negative values.

Let us start with a simple example in which we place ten crosses along a path starting with the beginning of the path ($$\meta {start pos} = 0$$) and ending at the end ($$\meta {end pos} = 1$$).

In the next example we place arrow shapes on the path instead of crosses. Note the use of the transform shape option to ensure that the nodes are actually rotated.

Using the key sequence number we can also “number” the nodes and even refer to them later on.

In the following example we use the distance info to place “length information” on a path:

• /pgf/decoration/reset marks(no value)

• Since mark options accumulate, there needs to be a way to “reset” things, so that any mark options set in an enclosing scope do not interfere. This option does exactly this. Note that when the code of a marking is executed, the markings are automatically reset.

As mentioned earlier, the decoration usually destroys the path. However, this is no longer the case when the following key is set:

• /pgf/decoration/mark connection node=node name (no default, initially empty)

• When this key is set to a non-empty node name while the decoration is being processed, the following happens: The marking code should, among possibly other things, define a node named node name. Then, the output path of this decoration will contain a line-to to “one end” of this node, followed by a moveto to the “other end” of the node. More precisely, the first end is given by the position on the border of node name that lies in the direction “from which the path heads toward the node” while the other end lies on the border “where the path heads away from the node”. Furthermore, this option causes the decoration to end with a line-to to the end instead of a move-to.

The net effect of all this is that when you decorate a straight line with one or more markings that contain just a node, the line will effectively connect these nodes.

Here are two examples that show how this works:

###### 50.6.1Arrow Tip Markings¶

Frequent markings that are hard to create correctly are arrow tips. For them, two special commands are available when the code of a mark option is executed. (They are only defined in this code):

• \arrow[options]{arrow end tip}

• This command simply draws the arrow end tip at the origin, pointing right. This is exactly what you need when you want to draw an arrow tip as a marking.

The options can only be given when TikZ is used. In this case, they are executed in a scope that contains the arrow tip.

Here is a more useful example:

• \arrowreversed[options]{arrow end tip}

• As above, only the arrow end tip is flipped and points in the other direction.

###### 50.6.2Footprint Markings¶
• TikZ Library decorations.footprints

• \usepgflibrary{decorations.footprints} % and plain and pure pgf
\usepgflibrary[decorations.footprints] % Cont and pure pgf
\usetikzlibrary{decorations.footprints} % and plain when using TikZ
\usetikzlibrary[decorations.footprints] % Cont when using TikZ

The decorations of this library can be used to decorate a path with little footprints, as if someone had “walked” along the path.

• Decoration footprints

You can influence the way this decoration looks using the following options:

• /pgf/decoration/foot length(initially 10pt)

• The length or size of the footprint itself. A larger value makes the footprint larger, but does not change the stride length.

• /pgf/decoration/stride length(initially 30pt)

• The length of strides. This is the distance between the beginnings of left footprints along the path.

• /pgf/decoration/foot sep(initially 4pt)

• The separation in the middle between the footprints. The footprints are moved away from the path by half this amount.

• /pgf/decoration/foot angle(initially 10)

• Footprints are rotated by this much.

• /pgf/decoration/foot of(initially human)

• The species whose footprints are shown. Possible values are:

.
Species Result
gnome
human
bird
felis silvestris
###### 50.6.3Shape Background Markings¶

The third library for adding markings uses the background paths of certain shapes. This library is included mostly for historical reasons, using the markings library is usually preferable.

• TikZ Library decorations.shapes

• \usepgflibrary{decorations.shapes} % and plain and pure pgf
\usepgflibrary[decorations.shapes] % Cont and pure pgf
\usetikzlibrary{decorations.shapes} % and plain when using TikZ
\usetikzlibrary[decorations.shapes] % Cont when using TikZ

This library defines decorations that use shapes or shape-like drawings to decorate a path. The following options are common options used by the decorations in this library:

• /pgf/decoration/shape width=dimension (no default, initially 2.5pt)

• The desired width of the shapes. For decorations that support varying shape sizes, this key sets both the start and end width (which can be overwritten using options like shape start width).

• /pgf/decoration/shape height=dimension (no default, initially 2.5pt)

• Works like the previous key, only for the height.

• /pgf/decoration/shape size=dimension(no default)

• Sets the desired width and height simultaneously.

For the exact places and macros where these keys store the values, please consult the beginning of the code of the library.

• Decoration crosses

• This decoration replaces the path by (diagonal) crosses. The following parameters influence the decoration:

• segment length determines the distance between (the centers of) consecutive crosses.

• shape height determines the height of each cross.

• shape width determines the width of each cross.

• Decoration triangles

• This decoration replaces the path by triangles that point along the path. The following parameters influence the decoration:

• segment length determines the distance between consecutive triangles.

• shape height determines the height of the triangle side that is orthogonal to the path.

• shape width determines the width of the triangle.

• Decoration shape backgrounds

• This is a general decoration that replaces the to-be-decorated path by repeated copies of the background path of an arbitrary shape that has previously been defined using the \pgfdeclareshape command (that is, you can use any shape in the shape libraries).

Please note that the background path of the shapes is used, but no nodes are created. This means that you cannot have text inside the shapes of this path, you cannot name them, or refer to them. Finally, this decoration will not work with shapes that depend strongly on the size of the text box (like the arrow shapes). If any of these restrictions pose a problem, use the markings library instead.

All shapes are positioned by the anchor that is specified via the anchor decoration option:

• /pgf/decoration/anchor=anchor (no default, initially center)

• The anchor used to position the shape backgrounds.

A shape background path is added at the start point of the path and, if the distance between the shapes is appropriate, at the end point of the path.

Keys for customizing specific shapes can be specified (e.g., star points, cloud puffs, kite angles, and so on). The size of the shape is “enforced” using transformations. This means that the shape is typeset with an empty text box and some default size values, resulting in an initial shape. This shape is then rescaled using coordinate transformations so that it has the desired size (which may vary as we travel along the to-be-decorated path). This means that settings involving angles and distances may not appear entirely accurate. More general options such as inner sep and minimum size will be ignored, but transformations can be applied to each segment as described below.

There are various keys to control the drawing of the shape decoration.

• /pgf/decoration/shape=shape name (no default, initially circle)

• The shape whose background path is used.

• /pgf/decoration/shape sep=spacing (no default, initially .25cm, between centers)

• Set the spacing between the shapes on the decorations path. This can be just a distance on its own, but the additional keywords between centers, and between borders (which must be preceded by a comma), specify that the distance is between the center anchors of the shapes or between the edges of the boundaries of the shape borders.

• This key overrides the shape sep key and forces the decoration to fit number shapes evenly across the path. If number is less than 1, then no shapes will be used. If number equals 1, then one shape is put in the middle of the path. The additional keywords by centers (the default, if no keyword is specified) and by borders can be used (both preceded by a comma), to specify how the distance between shapes is determined. These keywords will only have a noticeable effect if the shapes sizes differ over time.

• /pgf/decoration/shape sloped=boolean (no default, initially true)

• By default, shapes are rotated to the slope of the decorations path. If boolean is the value false, then this rotation is turned off. Internally this sets the -if \ifpgfshapedecorationsloped accordingly.

It is possible to scale the width and height of the shapes along the length of the decorations path. The shapes are scaled between the starting size and the ending size. The following keys customize the way the decoration shapes are scaled:

• /pgf/decoration/shape scaled=boolean (no default, initially false)

• If this key is set to false (which is the default), then only the start width and height are used. Note that the keys shape width and shape height set the start and end height simultaneously.

• /pgf/decoration/shape start width=length (no default, initially 2.5pt)

• The starting width of the shape.

• /pgf/decoration/shape start height=length (no default, initially 2.5pt)

• The starting height of the shape.

• /pgf/decoration/shape start size=length(style, no default)

• Sets both the start height and start width simultaneously.

• /pgf/decoration/shape end width=length (no default, initially 2.5pt)

• The recommended ending width of the shape. Note that this is the width that a shape will take only if it is drawn exactly at the end of the path.

• /pgf/decoration/shape end height=length(no default)

• The recommended ending height of the shape.

• /pgf/decoration/shape end size=length(style, no default)

• Set both the end height and end width simultaneously.

##### 50.7Text Decorations¶
• TikZ Library decorations.text

• \usepgflibrary{decorations.text} % and plain and pure pgf
\usepgflibrary[decorations.text] % Cont and pure pgf
\usetikzlibrary{decorations.text} % and plain when using TikZ
\usetikzlibrary[decorations.text] % Cont when using TikZ

The decoration in this library decorates the path with some text. This can be used to draw text that follows a curve.

• Decoration text along path

• This decoration decorates the path with text. This drawing of the text is a “side effect” of the decoration. The to-be-decorated path is only used to determine where the characters should be put and it is thrown away after the decoration is done. This is why no line is shown in the following example.

pgf “does its best” to typeset the text, however you should note the following points:

• • Each character in the text is typeset in a separate \hbox. This means that if you want fancy things like kerning or ligatures you will have to manually annotate the characters in the decoration text within a group, for example, W{\kern-1ptA}TER.

• • Each character is positioned using the center of its baseline. To move the text vertically (relative to the path), the additional decoration key raise should be used (see Section 24.4 for details).

• • No attempt is made to ensure characters do not overlap when the angle between segments is considerably less than 180$$^\circ$$ (this is tricky to do in without a huge processing overhead). In general this should not be too much of a problem, but, once again, kerning can be used in most cases to overcome any undesirable effects.

• • It is only possible to typeset text in math mode under considerable restrictions. Math mode is entered and exited using any character of category code 3 (e.g., in plain this is \$). Math subscripts and superscripts need to be contained within braces (e.g., {^y_i}) as do commands like \times or \cdot. However, even modestly complex mathematical typesetting is unlikely to be successful along a path (or even desirable).

• • Some inaccuracies in positioning may be particularly apparent at input segment boundaries. This can (unfortunately) only be solved on a case-by-case basis by individually kerning the offending characters within a group.

The following keys are used by the text decoration:

• /pgf/decoration/text=text (no default, initially empty)

• Sets the text to typeset along the curve. Consecutive spaces are ignored, so \ (or \space in ) should be used to insert multiple spaces. It is possible to format the text using normal formatting commands, such as \it, \bf and \color, within customizable delimiters. Initially these delimiters are both | (however, care will be needed regarding the category codes of delimiters – see below).

By following the first delimiter with +, the formatting commands are added to any existing formatting.

Internally, the text is stored in the macro \pgfdecorationtext. Any characters that have not been typeset when the end of the path has been reached will be stored in \pgfdecorationrestoftext.

• /pgf/decoration/text format delimiters={before}{after} (no default, initially {|}{})

• Set the characters that the text decoration will use to parse formatting commands. If after is empty, then before will be used for both delimiters. In general you should stick to characters whose category codes are 11 or 12. As + is used to indicate that the specified format commands are added to any existing ones, you should avoid using + as a delimiter.

• /pgf/decoration/text color=color (no default, initially black)

• The color of the text.

• /pgf/decoration/reverse path=boolean (no default, initially false)

• This key reverses the path. This is especially useful for typesetting text along different sides of curves.

• /pgf/decoration/text align={alignment options}(no default)

• This changes the key path to /pgf/decoration/text align and executes alignment options.

• /pgf/decoration/text align/align=alignment (no default, initially left)

• Aligns the text according to alignment, which should be one of left, right, or center.

• /pgf/decoration/text align/left(style, no value)

• Aligns the text to the left end of the path.

• /pgf/decoration/text align/right(style, no value)

• Aligns the text to the right end of the path.

• /pgf/decoration/text align/center(style, no value)

• Aligns the text to the center of the path.

• /pgf/decoration/text align/left indent=length (no default, initially 0pt)

• Specifies a distance which the automaton should move along before it starts typesetting the text.

• /pgf/decoration/text align/right indent=length (no default, initially 0pt)

• Specifies a distance before the end of the path, where the automaton should stop typesetting the text.

• /pgf/decoration/text align/fit to path=boolean (no default, initially false)

• This key makes the decoration automaton try to fit the text to the length of the path. The automaton shifts forward by a small amount between each character in order to fit the text to the path. If, however, the length of the text is longer than the length of the path (i.e., the automaton would have to shift backwards between characters) this key will have no effect.

• /pgf/decoration/text align/fit to path stretching spaces=boolean (no default, initially false)

• This key works like the previous key except the automaton shifts forward only for space characters (including \space, but excluding \ ).

• Decoration text effects along path

• This decoration is similar to the text along path decoration except that each character is inserted into the picture as a TikZ node, and node options (such as text, scale and opacity) can be used to create ‘text effects’.

There are some important differences between this decoration and the text along path decoration:

• • formatting (e.g., font and color) cannot be specified in the decoration text. They can only be specified using the keys described below.

• • as a consequence of using the TikZ node options, this decoration is only available in TikZ.

• • due to the number of computations involved, this is quite a slow decoration.

The following keys are shared with the text along path decoration:

• /pgf/decoration/text={text}(no default)

• Set the text this decoration will use. Braces can be used to group multiple characters together, or commands that should not be expanded until they are typeset, for example gr{\"o}{\ss}eren. You should not use the formatting delimiters or math mode characters that the text along path decoration supports.

• /pgf/decoration/text align=align(no default)

• This sets the alignment of the text along the path. The align argument should be left, right or center. Spreading the text out, or stretching the spaces between words is not supported.

The decoration text can be thought of as consisting of characters arranged in to sequences of letters to make words which are separated by a word separator. This, however, does not mean that you are limited to using only natural language as the decoration text.

In addition, it is possible to replace characters with TikZ code:

There are many keys and styles that can be used to add effects to the decoration text. Many of these keys have the parent path /pgf/decoration/text effects/, but for convenience, these keys can be accessed using the following key:

• /tikz/text effects={options}(no default)

• Execute every option in {options} with the key path for each option temporarily set to /pgf/decoration/text effects/.

The following keys can be used to customise the appearance of text in the text effects along path decoration.

• /pgf/decoration/text effects/every character(style, no value)

• Set the effects that will be applied to every character in the decoration text. The effects will typically be TikZ node options. Initially, this style is empty so the decoration simply positions nodes at the appropriate position along the path. In order to make the text ‘follow the path’ like the text along path decoration the following key can be added to the every character style.

• /pgf/decoration/text effects/text along path(style, no value)

• This style automatically sets the TikZ keys transform shape (to make the character slope with the path), anchor=baseline (to make the baseline of the characters ‘sit’ on the path) and inner xsep=0pt (to horizontally fit each node to the character it contains, reducing the spacing between characters).

• /pgf/decoration/text effects/characters={effects}(no default)

• Shorthand for the every character.

• /pgf/decoration/text effects/character number(style, no value)

• Specify additional effects for the character number.

• /pgf/decoration/text effects/every letter(style, no value)

• Specify additional effects for every letter (i.e., every character that isn’t the word separator) in the decoration text.

• /pgf/decoration/text effects/letter number(style, no value)

• Specify the effects for letter number in every word.

• /pgf/decoration/text effects/every first letter(style, no value)

• Specify additional effects for the first letter in every word.

• /pgf/decoration/text effects/every last letter(style, no value)

• Specify additional effects for the last letter in every word.

• /pgf/decoration/text effects/every word(style, no value)

• Specify additional effects for every word in the decoration text.

• /pgf/decoration/text effects/word number(style, no value)

• Specify additional effects for word number in the decoration text.

• /pgf/decoration/text effects/word m letter n(style, no value)

• Specify additional effects for letter n in word m in the decoration text.

• /pgf/decoration/text effects/every word separator(style, no value)

• Specify additional effects for every character that is a word separator.

• /pgf/decoration/text effects/word separator=character (no default, initially space)

• Specify the character that is to be used as the word separator. This must be a single character such as a or - or the special value space (which should be used to indicate that spaces should be used as the separator).

By default, the width for each character is calculated according to the bounding box of the node in which it is contained. However, if the node is rotated or slanted, or has a substantial inner sep, this bounding box will be quite big. The following key enables different effects to be applied to the node that is used to calculate the width.

• /pgf/decoration/text effects/every character width(style, no value)

• This style is applied to the (invisible) nodes used for calculating the width of a character node.

• /pgf/decoration/text effects/character widths={effects}(no default)

• Shorthand for the every character width style.

It is possible to parameterize effects, perhaps for doing calculations, or labelling nodes based on the number of the character in the decoration text. To access the number of the character, and the total number of characters the following keys can be used. However, these keys should not be used inside the style keys given above.

• /pgf/decoration/text effects/character count=macro(no default)

• Store the number of the character being typeset in macro.

• /pgf/decoration/text effects/character total=macro(no default)

• Store the total number of the characters in the decoration text in macro. This key can be used with the character count key to produce some quite pleasing effects:

• /pgf/decoration/text effects/letter count=macro(no default)

• Store the number of letter being typeset (i.e., the position of the character in the word) in macro. Numbering starts at 1 and the character acting as a word separator is numbered 0.

• /pgf/decoration/text/effetcs/letter total=macro(no default)

• Store the number of letters in the current word in macro. When the character is the word separator, this value is 0.

• /pgf/decoration/text effects/word count=macro(no default)

• Store the number of words in the decoration text in macro. Numbering starts at 1. When the character is the word separator, macro takes the number of the previous word. If the decoration text starts with a word separator macro will be 0.

• /pgf/decoration/text effects/word total=macro(no default)

• Store the total number of words in the decoration text in macro.

It is also possible to apply effects to specific characters such as coloring every instance of the character a, or changing the font of every T in the decoration text:

• /pgf/decoration/text effects/style characters={characters} with {effects}(no default)

• This key enables effects to be applied to every character in the decoration text that is specified in characters.

• /pgf/decoration/text effects/path from text={true or false} (default true)

• When this key is set to true and the decorated path consists only of a single point, the decoration will calculate the width of the decoration text using all the specified parameters as if the decorated path was actually a straight line starting from the given point. This ‘virtual’ straight line is then decorated with the text.

• /pgf/decoration/text effects/path from text angle=angle(no default)

• When used in conjunction with the path from text key, the straight line that is used as the decorated path is rotated by angle around the starting point.

• /pgf/decoration/text effects/fit text to path=true or false (default true)

• This key will make the decoration increase the space between characters so that the entire path is used by the decoration.

• /pgf/decoration/text effects/scale text to path=true or false (default true)

• This key will make the decoration scale the text so that the entire path is used by the decoration.

• /pgf/decoration/text effects/reverse text(no value)

• Reverse the order of the characters in the decoration text. This may be useful if using ‘right-to-left‘ languages. Unfortunately, any leading ‘soft’ spaces in the original text will be lost.

It is important to note that the reverse text key reverses the text before doing anything else. This means that the numbering of characters, letters and words will still be in the normal order, so any parameterized effects will have to take this into account. Alternatively, to get the numbering to follow the reversed text, it is possible to reverse the path and then invert the scale:

• /pgf/decoration/text effects/group letters(no value)

• Group sequences of letters together so they are treated as a single ‘character’.

The order in which the reverse text and group letters keys are applied is important:

• /pgf/decoration/text effects/repeat text=times(no default)

• Usually, when the decoration runs out of text, it simply stops. This key will make the decoration repeat the decoration text for the specified number of times. If no value is given the text will be repeated until the path is finished. There are two points to remember however. Firstly the numbering of characters, letters and words will be restarted each time the text is repeated. Secondly, the options for alignment, scaling or fitting the text to the path, fitting the path to the text, and so on, are computed using the decoration text before the decoration starts. If any of these options are given the behavior of the repeat text key is undefined, but typically it will be ignored.

• /pgf/decoration/text effects/character command=macro(no default)

• This key specifies a command that is executed when each character is placed in the node. The macro should be an ordinary macro which takes one argument. The argument will be a macro which when expanded will contain the current character.

• /pgf/decoration/text effects/replace characters=characters with {code}(no default)

• Replace the node for each character in characters with code. The code can be thought of as describing a little picture or marking which will be used instead of the character node. The origin will be the current point along the decoration path. Any transformations associated with the characters (e.g., applied with the every character or every letter styles) will also be applied to code.

##### 50.8Fractal Decorations¶
• TikZ Library decorations.fractals

• \usepgflibrary{decorations.fractals} % and plain and pure pgf
\usepgflibrary[decorations.fractals] % Cont and pure pgf
\usetikzlibrary{decorations.fractals} % and plain when using TikZ
\usetikzlibrary[decorations.fractals] % Cont when using TikZ

The decorations of this library can be used to create fractal lines. To use them, you typically have to apply the decoration repeatedly to an originally straight path.

• Decoration Koch curve type 1

• This decoration replaces a straight line by a “rectangular bump”. By repeatedly applying this replacement, different levels of the Koch curve fractal can be created. Its Hausdorff dimension is $$\log 5/\log 3$$.

• Decoration Koch curve type 2

• This decoration replaces a straight line by a “rectangular sine”. Its Hausdorff dimension is $$3/2$$.

• Decoration Koch snowflake

• This decoration replaces a straight line by a “line with a spike”. The Hausdorff dimension of Koch’s snowflake’s is $$\log 4/\log 3$$.

• Decoration Cantor set

• This decoration replaces a straight line by a “line with a gap in the middle”. The Hausdorff dimension of the Cantor set is $$\log 2/\log 3$$.