Cfrtjryk

I'm trying to add groups of subfigures like below, and LaTex is following.
However, the second captions starts little below than others.
How can I fix it?

documentclass[twocolumn]{article}

usepackage[demo]{graphicx}

usepackage{subcaption}



begin{document}

begin{figure*}

centering

captionsetup[subfigure]{labelformat=empty}

begin{subfigure}[b]{.16linewidth}

includegraphics[width=linewidth]{figure/a_1.png}

end{subfigure}

begin{subfigure}[b]{.16linewidth}

includegraphics[width=linewidth]{figure/a_2.png}

end{subfigure}

hfill

begin{subfigure}[b]{.16linewidth}

includegraphics[width=linewidth]{figure/b_1.png}

end{subfigure}

begin{subfigure}[b]{.16linewidth}

includegraphics[width=linewidth]{figure/b_2.png}

end{subfigure}

hfill

begin{subfigure}[b]{.16linewidth}

includegraphics[width=linewidth]{figure/c_1.png}

end{subfigure}

begin{subfigure}[b]{.16linewidth}

includegraphics[width=linewidth]{figure/c_2.png}

end{subfigure}

hfill

begin{subfigure}[b]{.16linewidth}

includegraphics[width=linewidth]{figure/a_3.png}

end{subfigure}

begin{subfigure}[b]{.16linewidth}

includegraphics[width=linewidth]{figure/a_4.png}

end{subfigure}

hfill

begin{subfigure}[b]{.16linewidth}

includegraphics[width=linewidth]{figure/b_3.png}

end{subfigure}

begin{subfigure}[b]{.16linewidth}

includegraphics[width=linewidth]{figure/b_4.png}

end{subfigure}

hfill

begin{subfigure}[b]{.16linewidth}

includegraphics[width=linewidth]{figure/c_3.png}

end{subfigure}

begin{subfigure}[b]{.16linewidth}

includegraphics[width=linewidth]{figure/c_4.png}

end{subfigure}

hfill

begin{subfigure}[b]{.32linewidth}

small textbf{Easy} [no duplicate]\

scriptsize

blah1\

end{subfigure}

hfill

begin{subfigure}[b]{.32linewidth}

small textbf{Middle} [two duplicate]\

scriptsize

blah2\

end{subfigure}

hfill

begin{subfigure}[b]{.32linewidth}

small textbf{Hard} [three duplicate]\

scriptsize

blah3

end{subfigure}

caption{sample1}

  label{fig:3}

end{figure*}

end{document}

For a quick fix of the issue you've encountered, you could change the final 3 instances of begin{subfigure}[b] to begin{subfigure}[t]. Better still, just omit the \ (double backslash) directives after blah1 and blah2: They're not needed, and they're messing up the vertical positioning of these subfigure enviroments.

That said, you may want to rethink your entire approach to using subfigure environments. Since you're not using caption directives with any of the 12+3= 15 subfigure environments, you could -- actually, should! -- replace all subfigure environments with minipage environments. In case you didn't know: a subfigure environment is nothing but a minipage environment that's been told what to do if it encounters a caption directive. Since there are no such caption directives, why incur the overhead?

Next, why even employ minipage environments to encase the 12 image files? It seems pointless to do so, as includegraphics lets you state the (relative) dimensions of the images directly.

Finally, since you have 12 includegraphics statements, it's a good idea to create a shortcut macro to automate the sizing of the images.

documentclass[twocolumn]{article}

usepackage[demo]{graphicx} % omit 'demo' option in real doc.

%% Handy shortcut macro:

newcommandinc[1]{includegraphics%

   [width=0.15linewidth,height=0.15linewidth]{#1}}



begin{document}

begin{figure*}

%% First row of images:

inc{figure/a_1.png}hspace{0.005linewidth}

inc{figure/a_2.png}hspace{fill}

inc{figure/b_1.png}hspace{0.005linewidth}

inc{figure/b_2.png}hspace{fill}

inc{figure/c_1.png}hspace{0.005linewidth}

inc{figure/c_2.png}



smallskip

%% Second row of images:

inc{figure/a_3.png}hspace{0.005linewidth}

inc{figure/a_4.png}hspace{fill}

inc{figure/b_3.png}hspace{0.005linewidth}

inc{figure/b_4.png}hspace{fill}

inc{figure/c_3.png}hspace{0.005linewidth}

inc{figure/c_4.png}



smallskip

% Row of captions

begin{minipage}{.305linewidth}  % 0.305=2*0.15+0.005

smalltextbf{Easy} [no duplicate]



scriptsize blah1

end{minipage}%

hspace{fill}

begin{minipage}{.305linewidth}

smalltextbf{Middle} [two duplicate]



scriptsize blah2

end{minipage}%

hspace{fill}

begin{minipage}{.305linewidth}

smalltextbf{Hard} [three duplicate]



scriptsize blah3

end{minipage}



caption{sample1}

label{fig:3}

end{figure*}

end{document}

i would use captions in subfigure environments and in one subfigure merge four your images:

documentclass[twocolumn]{article}

usepackage[demo]{graphicx}

usepackage{caption}

usepackage{subcaption}



begin{document}

    begin{figure*}

captionsetup[subfigure]{labelformat=empty}

begin{subfigure}[b]{.32linewidth}

includegraphics[width=0.48linewidth]{figure/a_1.png}

includegraphics[width=0.48linewidth]{figure/a_2.png}



smallskip

includegraphics[width=0.48linewidth]{figure/a_3.png}

includegraphics[width=0.48linewidth]{figure/a_4.png}

    caption{textbf{Easy} [no duplicate]newlinescriptsize

             blah1}

end{subfigure}

hfill

begin{subfigure}[b]{.32linewidth}

includegraphics[width=0.48linewidth]{figure/b_1.png}

includegraphics[width=0.48linewidth]{figure/b_2.png}



smallskip

includegraphics[width=0.48linewidth]{figure/b_3.png}

includegraphics[width=0.48linewidth]{figure/b_4.png}

    caption{textbf{Middle} [two duplicate]newlinescriptsize

             blah1}

end{subfigure}

hfill

begin{subfigure}[b]{.32linewidth}

includegraphics[width=0.48linewidth]{figure/c_1.png}

includegraphics[width=0.48linewidth]{figure/c_2.png}



smallskip

includegraphics[width=0.48linewidth]{figure/c_3.png}

includegraphics[width=0.48linewidth]{figure/c_4.png}

    caption{textbf{Hard} [three duplicate]newlinescriptsize

             blah1}

end{subfigure}

caption{sample1}

  label{fig:3}

    end{figure*}

end{document}