TiKZ pattern on an angle?

Question

I would like a result similar to that provided by pattern = sixpointed stars (or fivepointed; doesn't matter), but where the underlying grid is at an angle. I understand this can't be done with the pattern library directly, so I might have to do it with a couple of nested for loops and a bit of clipping.

Is there a standard - or simple - way of doing this? In particular, what is the easiest way of obtaining one star which I can then replicate?

Answer 1

The (very) new patterns.meta library allows for easier ways of specifying patterns and in particular allows a transformation to be applied to the pattern tiles.

It is still under development (there is no documentation yet), only supports PDF output, and is only available in the latest CVS version but is more-or-less stable (so you have been warned).

\documentclass[tikz,border=5]{standalone}
\usetikzlibrary{patterns.meta}
\tikzdeclarepattern{name=Stars,
  type=uncolored,
  tile bounding box={(-5pt,-5pt) and (5pt,5pt)},
  tiling size={(\tikztilesize, \tikztilesize)},
  parameters={\tikzstarpoints,\tikzstarradius,\tikzstarrotate,\tikztilesize},
  tiling transformation={rotate=\tikzstarrotate},
  keys={  
    points/.store count=\tikzstarpoints,   points=5,
    radius/.store length=\tikzstarradius,  radius=3pt,
    rotate/.set macro=\tikzstarrotate,     rotate=0,
    tile size/.store length=\tikztilesize, tile size=10pt
  },
  code={
    \pgfmathparse{180/\tikzstarpoints}\let\a=\pgfmathresult
    \fill (90:\tikzstarradius) \foreach \i in {1,...,\tikzstarpoints}{
      -- (90+2*\i*\a-\a:\tikzstarradius/2) -- (90+2*\i*\a:\tikzstarradius)
    } -- cycle;
  }
}   

\begin{document}
\begin{tikzpicture}
\draw [pattern=Stars, pattern color=blue]             (0,0) rectangle ++(2,2);
\draw [pattern={Stars[points=7, tile size=15pt]}]     (2,0) rectangle ++(2,2);
\draw [pattern={Stars[rotate=45]}, pattern color=red] (0,2) rectangle ++(2,2);
\draw [pattern={Stars[rotate=30,points=4,radius=5]}]  (2,2) rectangle ++(2,2);
\end{tikzpicture}
\end{document}