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author | Norbert Preining <norbert@preining.info> | 2019-09-02 13:46:59 +0900 |
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committer | Norbert Preining <norbert@preining.info> | 2019-09-02 13:46:59 +0900 |
commit | e0c6872cf40896c7be36b11dcc744620f10adf1d (patch) | |
tree | 60335e10d2f4354b0674ec22d7b53f0f8abee672 /graphics/pgf/base/doc/text-en/pgfmanual-en-base-patterns.tex |
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diff --git a/graphics/pgf/base/doc/text-en/pgfmanual-en-base-patterns.tex b/graphics/pgf/base/doc/text-en/pgfmanual-en-base-patterns.tex new file mode 100644 index 0000000000..a8f85fb4cf --- /dev/null +++ b/graphics/pgf/base/doc/text-en/pgfmanual-en-base-patterns.tex @@ -0,0 +1,233 @@ +% Copyright 2006 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{Patterns} +\label{section-patterns} + +\subsection{Overview} + +There are many ways of filling a path. First, you can fill it using a solid +color and this is also the fastest method. Second, you can also fill it using a +shading, which means that the color changes smoothly between two (or more) +different colors. Third, you can fill it using a tiling pattern and it is +explained in the following how this is done. + +A tiling pattern can be imagined as a rectangular tile (hence the name) on +which a small picture is painted. There is not a single tile, but +(conceptually) an infinite number of tiles, all showing the same picture, and +these tiles are arranged horizontally and vertically to fill the plane. When +you use a tiling pattern to fill a path, what happens is that the path clips +out a ``window'' through which we see part of this infinite plane. + +Patterns come in two versions: \emph{inherently colored patterns} and +\emph{form-only patterns}. (These are often called ``color patterns'' and +``uncolored patterns'', but these names are misleading since uncolored patterns +do have a color and the color changes. As I said, the name is misleading\dots) +An inherently colored pattern is just a colored tile like, say, a red star with +a black outline. A form-only pattern can be imagined as a tile that is a kind +of rubber stamp. When this pattern is used, the stamp is used to print copies +of the stamp picture onto the plane, but we can use a different stamp color +each time we use a form-only pattern. + +\pgfname\ provides a special support for patterns. You can declare a pattern +and then use it very much like a fill color. \pgfname\ directly maps patterns +to the pattern facilities of the underlying graphic languages (PostScript, +\textsc{pdf}, and \textsc{svg}). This means that filling a path using a pattern +will be nearly as fast as if you used a uniform color. + +There are a number of pitfalls and restrictions when using patterns. First, +once a pattern has been declared, you cannot change it anymore. In particular, +it is not possible to enlarge it or change the line width. Such flexibility +would require that the repeating of the pattern were not done by the graphic +language, but on the \pgfname\ level. This would make patterns orders of +magnitude slower to produce and to render. However, \pgfname{} does provide a +more-or-less successful emulation of ``mutable'' patterns, although internally, +a new (fixed) instance of a pattern is declared when the parameters of a +pattern change. + +Second, the phase of patterns is not well-defined, that is, it is not clear +where the origin of the ``first'' tile is. To be more precise, PostScript and +\textsc{pdf} on the one hand and \textsc{svg} on the other hand define the +origin differently. PostScript and \textsc{pdf} define a fixed origin that is +independent of where the path lies. This has the highly desirable effect that +if you use the same pattern to fill multiple paths, the outcome is the same as +if you had filled a single path consisting of the union of all these paths. By +comparison, \textsc{svg} uses the upper-left (?) corner of the path to be +filled as the origin. However, the \textsc{svg} specification is a bit vague on +this question. + + +\subsection{Declaring a Pattern} + +Before a pattern can be used, it must be declared. The following command is +used for this: + +\begin{command}{\pgfdeclarepatternformonly% + \opt{\oarg{variables}}% + \marg{name}% + \marg{bottom left}% + \marg{top right}% + \marg{tile size}% + \marg{code}% +} + This command declares a new form-only pattern. The \meta{name} is a name + for later reference. The two parameters \meta{lower left} and \meta{upper + right} must describe a bounding box that is large enough to encompass the + complete tile. + + The size of a tile is given by \meta{tile size}, that is, a tile is a + rectangle whose lower left corner is the origin and whose upper right + corner is given by \meta{tile size}. This might make you wonder why the + second and third parameters are needed. First, the bounding box might be + smaller than the tile size if the tile is larger than the picture on the + tile. Second, the bounding box might be bigger, in which case the picture + will ``bleed'' over the tile. + + The \meta{code} should be \pgfname\ code than can be protocolled. It should + not contain any color code. + % +\begin{codeexample}[] +\pgfdeclarepatternformonly{stars} +{\pgfpointorigin}{\pgfpoint{1cm}{1cm}} +{\pgfpoint{1cm}{1cm}} +{ + \pgftransformshift{\pgfpoint{.5cm}{.5cm}} + \pgfpathmoveto{\pgfpointpolar{0}{4mm}} + \pgfpathlineto{\pgfpointpolar{144}{4mm}} + \pgfpathlineto{\pgfpointpolar{288}{4mm}} + \pgfpathlineto{\pgfpointpolar{72}{4mm}} + \pgfpathlineto{\pgfpointpolar{216}{4mm}} + \pgfpathclose% + \pgfusepath{fill} +} +\begin{tikzpicture} + \filldraw[pattern=stars] (0,0) rectangle (1.5,2); + \filldraw[pattern=stars,pattern color=red] + (1.5,0) rectangle (3,2); +\end{tikzpicture} +\end{codeexample} + + The optional argument \meta{variables} consists of a comma separated list + of macros, registers or keys, representing the parameters of the pattern + that may vary. If a variable is a key, then the full path name must be used + (specifically, it must start with |/|). As an example, a list might look + like the following: |\mymacro,\mydimen,/pgf/my key|. Note that macros and + keys should be ``simple''. They should only store values in themselves. + + The effect of \meta{variables}, is the following: Normally, when this + argument is empty, once a pattern has been declared, it becomes ``frozen''. + This means that it is not possible to enlarge the pattern or change the + line width later on. By specifying \meta{variables}, no pattern is actually + created. Instead, the arguments are stored away (so the macros, registers + or keys do not have to be defined in advance). + + When the fill pattern is set, \pgfname{} checks if the pattern has already + been created with the \meta{variables} set to their current values + (\pgfname{} is usually ``smart enough'' to distinguish between macros, + registers and keys). If so, this already-declared-pattern is used as the + fill pattern. If not, a new instance of the pattern (which will have a + unique internal name) is declared using the current values of + \meta{variables}. These values are then saved and the fill pattern set + accordingly. + + The following shows an example of a pattern which varies according to the + values of the macro |\size|, the key |/tikz/radius|, and the \TeX{} + dimension |\thickness|. + % +\begin{codeexample}[] +\pgfdeclarepatternformonly[/tikz/radius,\thickness,\size]{rings} +{\pgfpoint{-0.5*\size}{-0.5*\size}} +{\pgfpoint{0.5*\size}{0.5*\size}} +{\pgfpoint{\size}{\size}} +{ + \pgfsetlinewidth{\thickness} + \pgfpathcircle\pgfpointorigin{\pgfkeysvalueof{/tikz/radius}} + \pgfusepath{stroke} +} +\newdimen\thickness +\tikzset{ + radius/.initial=4pt, + size/.store in=\size, size=20pt, + thickness/.code={\thickness=#1}, + thickness=0.75pt +} +\begin{tikzpicture}[rings/.style={pattern=rings}] + \filldraw [rings, radius=2pt, size=6pt] (0,0) rectangle +(1.5,2); + \filldraw [rings, radius=2pt, size=8pt] (2,0) rectangle +(1.5,2); + \filldraw [rings, radius=6pt, thickness=2pt] (0,2.5) rectangle +(1.5,2); + \filldraw [rings, radius=8pt, thickness=4pt] (2,2.5) rectangle +(1.5,2); +\end{tikzpicture} +\end{codeexample} + % +\end{command} + +\begin{command}{\pgfdeclarepatterninherentlycolored + \opt{\oarg{variables}} + \marg{name} + \marg{lower left} + \marg{upper right} + \marg{tile size} + \marg{code}% +} + This command works like |\pgfdeclarepatternuncolored|, only the pattern + will have an inherent color. To set the color, you should use \pgfname's + color commands, not the |\color| command, since this fill is not + protocolled. + % +\begin{codeexample}[] +\pgfdeclarepatterninherentlycolored{green stars} +{\pgfpointorigin}{\pgfpoint{1cm}{1cm}} +{\pgfpoint{1cm}{1cm}} +{ + \pgfsetfillcolor{green!50!black} + \pgftransformshift{\pgfpoint{.5cm}{.5cm}} + \pgfpathmoveto{\pgfpointpolar{0}{4mm}} + \pgfpathlineto{\pgfpointpolar{144}{4mm}} + \pgfpathlineto{\pgfpointpolar{288}{4mm}} + \pgfpathlineto{\pgfpointpolar{72}{4mm}} + \pgfpathlineto{\pgfpointpolar{216}{4mm}} + \pgfpathclose% + \pgfusepath{stroke,fill} +} +\begin{tikzpicture} + \filldraw[pattern=green stars] (0,0) rectangle (3,2); +\end{tikzpicture} +\end{codeexample} + % +\end{command} + + +\subsection{Setting a Pattern} + +Once a pattern has been declared, it can be used. + +\begin{command}{\pgfsetfillpattern\marg{name}\marg{color}} + This command specifies that paths that are filled should be filled with the + ``color'' by the pattern \meta{name}. For an inherently colored pattern, + the \meta{color} parameter is ignored. For form-only patterns, the + \meta{color} parameter specifies the color to be used for the pattern. + % +\begin{codeexample}[] +\begin{tikzpicture} + \pgfsetfillpattern{stars}{red} + \filldraw (0,0) rectangle (1.5,2); + + \pgfsetfillpattern{green stars}{red} + \filldraw (1.5,0) rectangle (3,2); +\end{tikzpicture} +\end{codeexample} + % +\end{command} + + +%%% Local Variables: +%%% mode: latex +%%% TeX-master: "pgfmanual" +%%% End: |