[Tex/LaTex] How to clip an image via a bezier-path

Question

I have a rectangular image that I can not change.

I'd like to clip the image with a Bézier path so I get one that is rectangular at the top and the sides but has a curve at the bottom, preferable without using additional packages.

Answer 1

I don't know of a way to clip an image without using additional packages (apart from graphicx, I assume). There is a way of doing it with TikZ, which is probably better than no solution.

This is based on the answers to the question Drawing on an image with TikZ. I've written a macro that takes an image name with the accompanying \includegraphics options and a TikZ path as arguments to either display the image overlaid with a grid and the path, or to use the path to clip the image. The behaviour is toggled using \tikzset{develop clipping path=true} to switch on the grid and the path display, and \tikzset{develop clipping path=false} to perform the actual clipping once the path has been developed.

    \documentclass{article}

    \usepackage{tikz}
    \usepackage{graphicx}

    \newif\ifdeveloppath
    \tikzset{/tikz/develop clipping path/.is if=developpath,
      /tikz/develop clipping path=true}

    \newcommand{\clippicture}[2]{
      \begin{tikzpicture}
    % Include the image to determine the size and set up the relative coordinate system. Enclose the \includegraphics in \phantom{} once the clipping path has been set up
    \ifdeveloppath
      \node[anchor=south west,inner sep=0] (image) at (0,0) {\includegraphics#1};
    \else
      \node[anchor=south west,inner sep=0] (image) at (0,0) {\phantom{\includegraphics#1}};
    \fi
    \pgfresetboundingbox
    \begin{scope}[x={(image.south east)},y={(image.north west)}]
      % Draw grid while developing clipping path
      \ifdeveloppath
        \draw[help lines,xstep=.1,ystep=.1] (0,0) grid (1,1);
        \foreach \x in {0,1,...,9} { \node [anchor=north] at (\x/10,0) {0.\x}; }
        \foreach \y in {0,1,...,9} { \node [anchor=east] at (0,\y/10) {0.\y}; }
        \draw[red, ultra thick] #2 -- cycle;
      \else
        % Use the path to clip, include the image
        \path[clip] #2 -- cycle;
        \node[anchor=south west,inner sep=0pt] {\includegraphics#1};
      \fi
    \end{scope}
    \end{tikzpicture}
    }

    \begin{document}
Show the image with a grid to help in finding the coordinates for the path.

    \clippicture{[width=0.8\textwidth]{some-image}}{(0.5,0.75) -- (0.90,0.75) -- (0.90,0.5) .. controls (0.8,-0.2) and (0.65,0.2) .. (0.5,0.3)}

    \tikzset{develop clipping path=false}
Done with developing the path. Do the actual clipping.

    \clippicture{[width=0.8\textwidth]{some-image}}{(0.5,0.75) -- (0.90,0.75) -- (0.90,0.5) .. controls (0.8,-0.2) and (0.65,0.2) .. (0.5,0.3)}
    \end{document}