How To Create Flowchart In Latex

Quick and dirty hack for the arrow: \draw[arrow] ([xshift=-0.5cm]Modify AC coefficients.south) -| ([xshift=3cm]Watermarked Image.north);

Please

note that you should not use \tikzstyle, this is obsolete.
also check that latin1 is really the appropriate encoding for your document. The vast majority of editors use utf8 by default.
don't misuse x for \times

          \documentclass{article}  \usepackage[latin1]{inputenc} \usepackage{tikz} \usetikzlibrary{shapes,arrows}  %%%< \usepackage{verbatim} \usepackage[active,tightpage]{preview} \PreviewEnvironment{tikzpicture} \setlength\PreviewBorder{5pt}% %%%>   \begin{document} \pagestyle{empty}  \tikzset {     arrow/.style={        ->,>=stealth} } % Define block styles \tikzstyle{decision} = [diamond, draw,       text width=4.5em, text badly centered, inner sep=0pt] \tikzstyle{block} = [rectangle, draw,       text width=5em, text centered, rounded corners, minimum height=4em]     \tikzstyle{block1} = [rectangle, draw,       text width=6em, text centered, rounded corners, minimum height=4em]     \tikzstyle{block2} = [rectangle, draw,       text width=15em, text centered, rounded corners, minimum height=4em]      \tikzstyle{block3} = [rectangle, draw,       text width=20em, text centered, rounded corners, minimum height=4em] \tikzstyle{line} = [draw, -latex']   \begin{tikzpicture}[node distance = 2.5cm, auto]     % Place nodes     \node [block3] (Watermarked Image) {Watermarked Image};    \node[decision, above of =Watermarked Image,node distance=4cm ] (Difference between selected coefficients) {Difference between selected coefficients };    \node [block, left of=Difference between selected coefficients, node distance=3.5cm] (Inverse DCT for each block)     {Inverse DCT for each block};    \node [block, right of=Difference between selected coefficients, node distance=3.5cm] (Modify AC coefficients)     {Modify AC coefficients and perform Inverse DCT for each block};    \node [block2, above of=Difference between selected coefficients] (Genetic Algorithm)     {Genetic Algorithm search DCT coefficients to find best option for insert watermark};    \node [block, above of=Genetic Algorithm] (DCT for each block)     {DCT for each block};    \node [block, left of=DCT for each block] (Watermark Message)     {Watermark Message};     \node [block, above of=DCT for each block] (8x8 Image Blocking)     {8x8 Image Blocking};     \node [block, above of=Watermark Message] (Host Image)     {Host Image};     % Draw edges   \path [line] (Host Image) -- (8x8 Image Blocking);   \path [line] (8x8 Image Blocking) -- (DCT for each block);       \path [line] (DCT for each block) -- (Genetic Algorithm);       %\path [line] (Watermark Message) -- (Genetic Algorithm);      %\path [line] (Modify AC coefficients) -- (Inverse DCT for each block);      %\path [line] (Inverse DCT for each block) -- (Watermarked Image);      \path [line] (Genetic Algorithm) -- (Difference between selected coefficients);      \path [line] (Difference between selected coefficients) -- node {yes} (Inverse DCT for each block);     \path [line] (Difference between selected coefficients) -- node {no}(Modify AC coefficients);         \coordinate (n2nl) at ([xshift=-2cm]Genetic Algorithm.north);     \coordinate (n2nr) at ([xshift=-3cm]Watermarked Image.north);     \coordinate (n2ns) at ([xshift=3cm]Watermarked Image.east);      \draw[arrow] (Watermark Message.south -| n2nl) -- (n2nl);      \draw[arrow] (Inverse DCT for each block.south -| n2nr) -- (n2nr); %    \draw[arrow] (Modify AC coefficients.south -| n2ns) -- (n2ns);      \draw[arrow] ([xshift=-0.5cm]Modify AC coefficients.south) -| ([xshift=3cm]Watermarked Image.north);  \end{tikzpicture}   \end{document}

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