Changing graph to logarithmic scale and adding a 2nd Y-Axis

Question

Since the values for the "FPGA" (Brown) chart is really small(0.0002, green doesnt show up), i wanted to use logarithmic scale instead. I tried using "ymode=log," but it makes the chart go wonky.

Additionally, I want to also add another right hand, y-axis to compare the throughput data, each bar graph having a value ranging from 0-2, probably a disconnected line plot.

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.17}
\begin{document}\begin{figure}[!h]
\centering
\begin{tikzpicture}
\begin{axis}[
    ybar,
    ymin=0,
    %enlargelimits=0.15,
                legend image code/.code={%
                    \draw[#1, draw=none] (0cm,-0.1cm) rectangle (0.6cm,0.1cm);
                },  
    legend style={at={(0.5,-0.10)},
      anchor=north,legend columns=-1},
    ylabel={Execution Time (ms)},
    symbolic x coords={RGB2GRAY,Gaussian,Box,Sobel},
    xtick=data,
    nodes near coords,
    nodes near coords align={vertical},
    ]
\addplot coordinates {(RGB2GRAY,33) (Gaussian,54)  (Box,127) (Sobel,246)  };%CPU
\addplot [fill=teal!]  coordinates {(RGB2GRAY,8.221) (Gaussian,13.3254)  (Box,14.958) (Sobel,29.935)  };%GPU
\addplot coordinates {(RGB2GRAY,20.234959834) (Gaussian,26.492609995)  (Box,27.353843832) (Sobel,45.59262995) };%FPGA
\legend{CPU,GPU,FPGA}
\end{axis}
\end{tikzpicture}
\caption{Algorithms Excluding Image Read/Write}
\label{imageexclude}
\end{figure}
\end{document}

Answer 1

This is not a full answer because the result is not pretty. Rather this is to tell you that ymode=log does work, at least in principle. The reason why the results look "wonky" is that by default log origin is set to 1, so some of the bars hang in the air. Changing this and putting repeating keys in a style (I actually do not know why ymode=log cannot be part of the style but this only one key) yields

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.17}
\begin{document}
\begin{figure}[!h]
\centering
\begin{tikzpicture}
\pgfplotsset{Freon axis/.style={ybar,
    ymin=0.00001,ymax=10000,%<- added ymax
    %enlargelimits=0.15,
                legend image code/.code={%
                    \draw[#1, draw=none] (0cm,-0.1cm) rectangle (0.6cm,0.1cm);
                },  
    legend style={at={(0.5,-0.10)},
      anchor=north,legend columns=-1},
    symbolic x coords={RGB2GRAY,Gaussian,Box, Sobel},
    xtick=data,
    nodes near coords,
    nodes near coords style={anchor=east,rotate=-90,inner xsep=1pt},
    log origin=infty
}}
\begin{axis}[Freon axis,ymode=log,ylabel={Execution Time (ms)}]
\addplot coordinates {(RGB2GRAY,54) (Gaussian,86)  (Box,154) (Sobel,268)  };%CPU
\addplot coordinates {(RGB2GRAY,170.71) (Gaussian, 172.065)  (Box,193.72) (Sobel,215.38)  };%GPU
\addplot coordinates {(RGB2GRAY,20.234959834) (Gaussian,26.492609995)  (Box,27.353843832) (Sobel,45.59262995) };%FPGA
\legend{CPU,GPU,FPGA}
\end{axis}


\begin{axis}[Freon axis,ymode=log,axis y line=right,ytick=\empty,
    ylabel={Throughput}]
\addplot [fill=green] coordinates {(RGB2GRAY,21) (Gaussian,32)  (Box,27) (Sobel,40)  };%CPU
\addplot [fill=green] coordinates {(RGB2GRAY,162.49) (Gaussian, 158.74)  (Box,178.76) (Sobel,169.79)  };%GPU
\addplot [fill=green] coordinates {(RGB2GRAY,0.0002) (Gaussian,0.0002)  (Box,0.0002) (Sobel,0.0002) };%FPGA
\end{axis}
\end{tikzpicture}
\caption{Algorithms Including Image Read/Write.}
\end{figure}
\end{document}

This is logarithmic but not pretty since now the brown bars grew but the red ones became too tiny. One could install a user transformation but I am not sure if this will then provide the viewer with the information you want to communicate.