Adjust recalculated figure size based on ratio instead of difference

.gitignore

@@ -0,0 +1,22 @@
+
+*.dpth
+
+*.log
+
+*.md5
+
+*.pdf
+
+*.dep
+
+*.aux
+
+*.auxlock
+
+test-tikzscale.synctex.gz
+
+*.ins
+
+*.sty
+
+README.txt

groupplot.tikz

@@ -0,0 +1,26 @@
+\begin{tikzpicture}
+	\begin{groupplot}[
+		group style={
+			group size=2 by 2,
+			y descriptions at=edge left,
+			x descriptions at=edge bottom
+		},
+		xlabel=$x$,
+		ylabel=$y$	
+		]
+
+		\nextgroupplot
+		\addplot {x^2 - x + 4};
+
+		\nextgroupplot
+		\addplot {x^2 - x + 4};
+
+		\nextgroupplot
+		\addplot {x^2 - x + 4};
+
+		\nextgroupplot
+		\addplot {x^2 - x + 4};
+
+	\end{groupplot}
+
+\end{tikzpicture}

test-tikzscale.tex

@@ -6,6 +6,7 @@
 \usepackage{pgfplots}
 \usepackage{tikz-3dplot}
 \usetikzlibrary{backgrounds}
+\usepgfplotslibrary{groupplots}
 \usepackage{currfile}
 \usepackage{lmodern}
 % Use the package subcaption to test the subfigure command
@@ -57,6 +58,12 @@
 			\includegraphics{pgfplots-test}%
 		\item Use pgfplots with given width and height\\%
 			\includegraphics[width=\linewidth,height=0.3\linewidth]{pgfplots-test}%
+		\item Use pgfplots with a 2x2 groupplot with a given total width\\%
+			\includegraphics[width=\linewidth]{groupplot}
+		\item Use pgfplots with a 2x2 groupplot with given total width and height\\%
+			\includegraphics[width=\linewidth,height=0.5\linewidth]{groupplot}
+		\item Use pgfplots with a 2x2 groupplot with given total width and axis ratio\\%
+			\includegraphics[width=\linewidth,axisratio=0.5]{groupplot}
 		\item Use includegraphics with only a node\\%
 			\includegraphics{testNode.tikz}%
 % 		\item Use includegraphics with scaling only a node results in an error\\%
@@ -121,4 +128,4 @@
 		\end{subfigure}
 	\end{figure}
 
-\end{document}
+\end{document}

tikzscale.dtx

@@ -1583,8 +1583,8 @@ and the derived files           tikzscale.ins,
 %    \end{macrocode}
 			% Correct the dimension by the error. Use a global assignment, as each iteration in the loop is put into a separate group.
 %    \begin{macrocode}
-			\pgfmathsetglobalmacro{\tikzscale@width}{\tikzscale@width - \widthDifference}%
-			\pgfmathsetglobalmacro{\tikzscale@height}{\tikzscale@height - \heightDifference}%
+			\pgfmathsetglobalmacro{\tikzscale@width}{\requestedWidth / \wd\tikzscale@measuredSize * \tikzscale@width}%
+			\pgfmathsetglobalmacro{\tikzscale@height}{\requestedHeight / \ht\tikzscale@measuredSize * \tikzscale@height}%
 		}{%
 			\breakforeach
 		}%
@@ -1644,10 +1644,10 @@ and the derived files           tikzscale.ins,
 %    \begin{macrocode}
 		\tikzscale@ifSizeDifference{\sizeDifference}{%
 			\tikzscale@ifIsWidth{#1}{%
-				\pgfmathsetglobalmacro{\tikzscale@width}{\tikzscale@width - \sizeDifference}%
+				\pgfmathsetglobalmacro{\tikzscale@width}{\requestedSize / \measuredSize * \tikzscale@width}%
 				\pgfmathsetglobalmacro{\tikzscale@height}{\tikzscale@width / \requestedAxisRatio}%
 			}{%
-				\pgfmathsetglobalmacro{\tikzscale@height}{\tikzscale@height - \sizeDifference}%
+				\pgfmathsetglobalmacro{\tikzscale@height}{\requestedSize / \measuredSize * \tikzscale@height}%
 				\pgfmathsetglobalmacro{\tikzscale@width}{\tikzscale@height * \requestedAxisRatio}%
 			}%
 			\tikzscale@ifSizeDifference{\sizeDifference-\tikzscale@oldSizeDifference}{%