Bib change

main.aux

 \relax 
 \providecommand\hyper@newdestlabel[2]{}
-\@nameuse{bbl@beforestart}
 \providecommand\HyperFirstAtBeginDocument{\AtBeginDocument}
 \HyperFirstAtBeginDocument{\ifx\hyper@anchor\@undefined
 \global\let\oldcontentsline\contentsline
@@ -22,7 +21,6 @@
 \citation{PNGdetails}
 \citation{LZW}
 \citation{PNGdetails}
-\babel@aux{english}{}
 \@writefile{toc}{\contentsline {section}{\numberline {1}Introduction}{1}{section.1}\protected@file@percent }
 \@writefile{lof}{\contentsline {figure}{\numberline {1}{\ignorespaces The other 4 pixels are used to find the value of the 5th.\relax }}{1}{figure.caption.1}\protected@file@percent }
 \providecommand*\caption@xref[2]{\@setref\relax\@undefined{#1}}

main.dep

@@ -8,8 +8,6 @@
   *{package}{caption3}    {2020/01/03 v1.8h}
   *{package}{keyval}      {2014/10/28 v1.15}
   *{package}{subcaption}  {2020/01/22 v1.3d}
-  *{package}{babel}       {2020/02/14 v3.40}
-  *{file}   {english.ldf} {2017/06/06 v3.3r}
   *{package}{amsmath}     {2020/01/20 v2.17e}
   *{package}{amstext}     {2000/06/29 v2.01}
   *{package}{amsgen}      {1999/11/30 v2.0}

main.tex

@@ -7,8 +7,6 @@
 \usepackage{caption}
 \usepackage{subcaption}
 % Language setting
-% Replace `english' with e.g. `spanish' to change the document language
-\usepackage[english]{babel}
 
 % Set page size and margins
 % Replace `letterpaper' with `a4paper' for UK/EU standard size