[Tex/LaTex] Drawing a flag in Tikz!

tikz-pgf

I have some trouble with tikz. I wanted to draw a flag in Tikz – but that with minimal success. Here a sketch:
Sketch

The sketch is not how it should look like: the letters are just there so I am able to tell you what I actually wanted. The black rectangles shouldn't be there either, it should just show you the regions. It should just look like a green rectangle on a red rectangle with a star in the middle.

The letters are coordinates (in px). Here the coordinates:

The flag edges:

N=(0, 300)
M=(450, 0)

The star edges:

A=(200, 180)
B=(185, 135)
C=(225, 205)
D=(265, 135)
E=(250, 180)

Here is what I tried:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{shapes,snakes}
\usepackage[left=2cm,right=2cm,top=2cm,bottom=2cm]{geometry}
\usepackage{xcolor}


\definecolor{grun}{HTML}{239d48}%green - colour of the top rectangle
\definecolor{rot}{HTML}{bf0028}%red - colour of the bottom rectangle
\definecolor{gelb}{HTML}{f6ec0f}%yellow - colour of the star


\begin{document}

\begin{tikzpicture}
\fill[fill=grun] (0, 0) rectangle (12, 4.5);
\fill[fill=red] (0,4.5) rectangle (12, 9);
\end{tikzpicture}

\end{document}

Problems:
I don't know why definecolor don't work for "rot" and "gelb". I don't know how to define the units for tikz (so instead of using cm I could write the coordinates in px and get an result). I don't know how to draw the star.

Bonus question:
Is it possible to play with the scale of the done tikzpicture (so make it fill the whole page)? I thought of something like minipage? But that is not an important question, I am just curious for next Tikz projects.

Kind regards and thank you in advance!

Best Answer

Since adequate answers have already been given, I've felt free to do this picture with MetaPost.

For me it was an occasion to use some recent features of the luamplib package, (which gives an interface to MetaPost in LuaLaTeX). More precisely, I've made use of the px unit (which I didn't know of) thanks to the \mpdim command, and of the integration of colors defined by the xcolor package, via the \mpcolor command.

The rectangle's dimensions follow the OP's first wishes, except for the star, for which it seems that several points are missing. So I've included a star of my own.

Edit I've made some minor changes, for the flag to be more like Burkina-Faso's official one, the way Paul Gaborit reports in its comment on the OP's question. So the red and green parts are reversed, and the star diameter is exactly one-third of the flag's height.

\documentclass{standalone}
\usepackage{luamplib, xcolor}

\definecolor{grun}{HTML}{239D48}%green - colour of the top rectangle
\definecolor{rot}{HTML}{BF0028}%red - colour of the bottom rectangle
\definecolor{gelb}{HTML}{F6eC0F}%yellow - colour of the star

\begin{document}
\begin{mplibcode}

u := \mpdim{1px}; % Unit length

beginfig(1);
    z = u*(450, 300); path rect; rect = unitsquare xscaled x yscaled .5y;
    % Star summits (I was not able to use the OP's given coordinates)
    pair S[]; S0 = y/6*right rotated 18;    
    for i = 2 step 2 until 8: S[i] := S[i-2] rotated 72; endfor
    for i = 1 step 2 until 9:
        S[i] = whatever[S[(i-3) mod 10], S[(i+1) mod 10]] = whatever[S[i-1], S[(i+3) mod 10]];
    endfor
    % Drawings
    fill rect withcolor \mpcolor{grun}; 
    fill rect shifted (0, .5y) withcolor \mpcolor{rot};
    fill S0 for i = 1 upto 9: -- S[i] endfor -- cycle shifted .5z withcolor \mpcolor{gelb};
endfig;

\end{mplibcode}
\end{document}

enter image description here

Related Solutions

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

The source of the difficulty is that ellipses are constructed in a particular way in TikZ. They are paths that start from the x-axis and proceed counter-clockwise around their centre. The vast majority of the time, the exact parametrisation doesn't matter. You appear to have found the one situation where it does!

In the actual question, you only want to be able to mirror the ellipse, and so draw it starting from the negative x-axis (the title of the question suggests a more flexible approach). That's actually not too hard since we can exploit the symmetry of the ellipse. The key is to provide it with a negative x-radius, since then it will start from the negative x-axis (and proceed clockwise, but we could correct for that by negating the y-radius as well). To do this, we interrupt the call from the node shape to the drawing command and flip the sign of the x-radius. The simplest way to do this is to redefine the \pgfpathellipse macro to do the negation and then call the original macro. The following code does this.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations,shapes,decorations.markings}
\makeatletter
\let\origpgfpathellipse=\pgfpathellipse
\def\revpgfpathellipse#1#2#3{%
  #2%
  \pgf@xa=-\pgf@x
  \origpgfpathellipse{#1}{\pgfqpoint{\pgf@xa}{0pt}}{#3}}
\makeatother

\tikzset{
  reversed ellipse/.style={
    ellipse,
    reverse the ellipse%
  },
  reverse the ellipse/.code={
    \let\pgfpathellipse=\revpgfpathellipse
  }
}
\begin{document}
\begin{tikzpicture}
\node[ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,0) {hello world};

\node[reversed ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,-2) {hello world};
\end{tikzpicture}

\end{document}

Here's the result:

rotated ellipse

(the arrow got clipped, but you can see where it lies)

[Tex/LaTex] TikZ: Drawing an arc from an intersection to an intersection

A solution which allows to draw intersection segments of any two intersections is available as tikz library fillbetween.

This library works as general purpose tikz library, but it is shipped with pgfplots and you need to load pgfplots in order to make it work:

\documentclass{standalone}

\usepackage{tikz}
\usepackage{pgfplots}
\usetikzlibrary{fillbetween}

\begin{document}

\begin{tikzpicture}

\draw [name path=red,red] (120:1.06) circle (1.9);
%\draw [name path=yellow,yellow] (0:1.06) circle (2.12);
\draw [name path=green,green!50!black] (0:0.77) circle (2.41);
\draw [name path=blue,blue] (0:0) circle (1.06);

% substitute this temp path by `\path` to make it invisible:
\draw[name path=temp1, intersection segments={of=red and blue,sequence=L1}];
\draw[red,-stealth,ultra thick, intersection segments={of=temp1 and green,sequence=L3}];

\end{tikzpicture}

\end{document}

enter image description here

The key intersection segments is described in all detail in the pgfplots reference manual section "5.6.6 Intersection Segment Recombination"; the key idea in this case is to

create a temporary path temp1 which is the first intersection segment of red and blue, more precisely, it is the first intersection segment in the Left argument in red and blue : red. This path is drawn as thin black path. Substitute its \draw statement by \path to make it invisible.
Compute the desired intersection segment by intersecting temp1 and green and use the correct intersection segment. By trial and error I figured that it is the third segment of path temp1 which is written as L3 (L = left argument in temp1 and green and 3 means third segment of that path).

The argument involves some trial and error because fillbetween is unaware of the fact that end and startpoint are connected -- and we as end users do not see start and end point.

Note that you can connect these path segments with other paths. If such an intersection segment should be the continuation of another path, use -- as before the first argument in sequence. This allows to fill paths segments:

\documentclass{standalone}

\usepackage{tikz}
\usepackage{pgfplots}
\usetikzlibrary{fillbetween}

\begin{document}

\begin{tikzpicture}

\draw [name path=red,red] (120:1.06) circle (1.9);
%\draw [name path=yellow,yellow] (0:1.06) circle (2.12);
\draw [name path=green,green!50!black] (0:0.77) circle (2.41);
\draw [name path=blue,blue] (0:0) circle (1.06);

% substitute this temp path by `\path` to make it invisible:
\draw[name path=temp1, intersection segments={of=red and blue,sequence=L1}];
\draw[red,fill=blue,-stealth,ultra thick, intersection segments={of=temp1 and green,sequence=L3}]  
    [intersection segments={of=temp1 and green, sequence={--R2}}]
;

\end{tikzpicture}

\end{document}

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

[Tex/LaTex] TikZ: Drawing an arc from an intersection to an intersection

Related Question