Faded drop-shadow using tikz-based rounded rectangle?

Question

Background

Epigraphs are in a box with rounded corners. The boxes have a drop-shadow.

Example

Picture #1 shows a shadow, while Picture #2 shows a shadow that fades out (soft blur):

1. 
2. 

Problem

The code for Picture #1, which is relatively simple, resembles:

\tikzstyle{epibox} = [
  draw=epigraphbordercolour,
  shade,
  top color=epigraphfillcolour!40,
  bottom color=epigraphfillcolour!5,
  drop shadow=dropshadowcolour,
  very thick,
  rectangle,
  rounded corners,
  inner sep=10pt,
  inner ysep=15pt
]

Related

• What's wrong with the fading of this TikZ node's shadow?
• http://www.texample.net/tikz/examples/pgf-version-2/

Question

How do you make a drop-shadow fade out using Tikz, such as Picture #2?

Answer 1

You could use the pgf-blur package, which gives you this:

In fact, it can add a "faded" drop shadow to pretty much anything:

The shadow fading is not continuous, like in the previously accepted answer. It fades in a number of discrete steps, but that number can be changed, see the documentation.

Here's the code for the examples:

\documentclass{article}
\usepackage{tikz}

\usetikzlibrary{shadows.blur}
\usetikzlibrary{shapes.symbols}

\begin{document}


\begin{center}
  \begin{tikzpicture}
    \node[draw=none,shade,
      top color=blue!40,
      bottom color=blue!5,
      rounded corners=6pt,
      blur shadow={shadow blur steps=5}
    ] {\sffamily\bfseries\large A pretty box};

    \node[tape,draw=none,shade,
      top color=blue!40,
      bottom color=blue!5,
      rounded corners=1pt,
      blur shadow={shadow blur steps=5,shadow blur extra rounding=1.3pt}
    ] at (5,0){\sffamily\bfseries\large Another pretty box};
  \end{tikzpicture}
\end{center}

\end{document}

Edit

Sometimes, PDF renderers will show a dark line in the center of the shadow. This is due to the way they handle anti-aliasing and clipping. To avoid this:

1. Use pgf-blur v1.01, which tries hard to hide this artefact
2. In Acrobat, turn off the "Page Display" preference "Enhance thin lines". These shadows consist of many thin lines, and they won't look good if Acrobat changes their width
3. Don't use too many blur shadow steps. It looks best if you have about two pixels per step at viewing resolution.

Answer 2

The following isn't entirely correct (it doesn't take rounded corners into account), but should suffice for most applications. Note that if you want to replace the shading by fading (i.e. use actual transparency), you will probably have to add clipping to the circles (so that they don't overlap with the rectangles). Also note that the effect seems to be rendered slightly incorrectly in Evince (and maybe some other pdf viewers too; the image is from the Linux version of Acrobat Reader).

\documentclass{article}    
\usepackage{tikz}
\usetikzlibrary{calc}

\begin{document}

% some parameters for customization
\def\shadowshift{5pt,-10pt}
\def\shadowradius{10pt}

% this draws a shadow under a rectangle node
\newcommand\drawshadow[1]{
    \begin{pgfonlayer}{shadow}
        \shade[white,inner color=black,outer color=white] ($(#1.south west)+(\shadowshift)+(\shadowradius/2,\shadowradius/2)$) circle (\shadowradius);
        \shade[white,inner color=black,outer color=white] ($(#1.north west)+(\shadowshift)+(\shadowradius/2,-\shadowradius/2)$) circle (\shadowradius);
        \shade[white,inner color=black,outer color=white] ($(#1.south east)+(\shadowshift)+(-\shadowradius/2,\shadowradius/2)$) circle (\shadowradius);
        \shade[white,inner color=black,outer color=white] ($(#1.north east)+(\shadowshift)+(-\shadowradius/2,-\shadowradius/2)$) circle (\shadowradius);
        \shade[top color=black,bottom color=white] ($(#1.south west)+(\shadowshift)+(\shadowradius/2,-\shadowradius/2)$) rectangle ($(#1.south east)+(\shadowshift)+(-\shadowradius/2,\shadowradius/2)$);
        \shade[left color=black,right color=white] ($(#1.south east)+(\shadowshift)+(-\shadowradius/2,\shadowradius/2)$) rectangle ($(#1.north east)+(\shadowshift)+(\shadowradius/2,-\shadowradius/2)$);
        \shade[bottom color=black,top color=white] ($(#1.north west)+(\shadowshift)+(\shadowradius/2,-\shadowradius/2)$) rectangle ($(#1.north east)+(\shadowshift)+(-\shadowradius/2,\shadowradius/2)$);
        \shade[white,right color=black,left color=white] ($(#1.south west)+(\shadowshift)+(-\shadowradius/2,\shadowradius/2)$) rectangle ($(#1.north west)+(\shadowshift)+(\shadowradius/2,-\shadowradius/2)$);
        \filldraw ($(#1.south west)+(\shadowshift)+(\shadowradius/2,\shadowradius/2)$) rectangle ($(#1.north east)+(\shadowshift)-(\shadowradius/2,\shadowradius/2)$);
    \end{pgfonlayer}
}

% create a shadow layer, so that we don't need to worry about overdrawing other things
\pgfdeclarelayer{shadow} 
\pgfsetlayers{shadow,main}

\begin{tikzpicture}
    \node [fill=blue,rectangle,rounded corners,minimum height=2cm,minimum width=2cm] (box) {};
    \drawshadow{box}
\end{tikzpicture}  
\end{document}

Answer 3

Sorry but my english language is poor, now you question is more easy to understand !

\documentclass{article}  
\usepackage{xcolor}
\usepackage{tikz}
\usetikzlibrary{shadows,fadings}

\begin{document}  
 \begin{tikzpicture} 
   \draw [help lines] (0,0) grid (3,2); 
   \filldraw [drop shadow={top color=black,
              bottom color=white,
              shadow xshift=1em,
              shadow yshift=-1em,
              rounded corners },
              rounded corners,
              top color= blue, bottom color=white]
(0,0) rectangle (6,3);

\end{tikzpicture} 
\end{document} 

Answer 4

You forgot a lot of things

1. You need to define layers (from the last link but it's very tricky but good from Mark Wibrow)

   \makeatletter
   \let\tikz@preaction@layer=\pgfutil@empty     
   \tikzset{preaction layer/.store in=\tikz@preaction@layer} 
   \makeatother
   
   \pgfdeclarelayer{shadow} 
   \pgfsetlayers{shadow,main}
   

2. Now you can define use shadow

   \tikzstyle{use shadow} = [
       copy shadow={%
         preaction layer=shadow,
         fill=gray!25,
         draw=none,
         shadow xshift=1em,
         shadow yshift=-1em
      }]   
   

3. next you need to define `epibox

   \tikzstyle{epibox} = [
     draw=epigraphbordercolour,
     shade,
     top color=epigraphfillcolour!40,
     bottom color=epigraphfillcolour!5,
     %drop shadow=dropshadowcolour,
     use shadow,
     very thick,
     rectangle,
     rounded corners,
     inner sep=10pt,
     inner ysep=15pt
   ]
   

with

\tikzstyle{use shadow} = [
      preaction layer=shadow,
      fill=gray!25,
      draw=none,
      shadow xshift=1em,
      shadow yshift=-1em
    ] 

you get :

I don't know exactly what you want, perhaps it's a mix of the two codes.

I think it's preferable now to use \tikset{use shadow/.style =...}}