SetDirectory["C:\\drorbn\\AcademicPensieve\\Classes\\14-240"]

Make::usage = "Make[targets, sources, action] makes a target, or a list of targets, given sources, or a list of sources, in the style of the unix 'make' command.";
Make[target_String, sources_, action_Hold] := Make[Evaluate@{target}, sources, action];
Make[targets_, source_String, action__Hold] := Make[targets, Evaluate@{source}, action];
Make[targets_List, sources_List, action_Hold] := Module[{},
If[
(And @@ ((FileType[#] =!= None)& /@ sources)) &&
Or[
Or @@ ((FileType[#]===None)& /@ targets),
Min[AbsoluteTime[FileDate[#]]& /@ targets] < Max[AbsoluteTime[FileDate[#]]& /@ sources]
],
Print["Making ",targets, " ..."];
ReleaseHold[action]
]
];

?Make

name= "What_is_This_Class_AboutQ";
target =name<>".png";
source = "one/"<>name<>".pdf";
Make[target, source, Hold[
Read["!convert -density 150 -background white -alpha remove "<>source<>" "<>target];
]]

name= "TheComplexField";
target =name<>".png";
source = "nb/"<>name<>".pdf";
Make[target, source, Hold[
Read["!convert -density 200 -background white -alpha remove -trim "<>source<>" "<>target];
Read["!convert +append "<>name<>"-0.png "<>name<>"-1.png "<>target];
DeleteFile[{name<>"-0.png", name<>"-1.png"}]
]]

{
  "TitleNotes" -> "<span style=\"color: red;\">
    Warning - the material here is my personal <a
    href=\"http://drorbn.net/index.php?title=14-240\">MAT 240 \"Algebra I\"</a>
    notebook for 2014. No guarantee of any kind on
    anything that appears here.
    </span><p>",
"ImageComments" -> {
"LionAndHuman.png" -> "From Project Gutenberg's Cautionary Tales for Children, by Hilaire Belloc, <a href=http://www.gutenberg.org/files/27424/27424-h/27424-h.htm>http://www.gutenberg.org/files/27424/27424-h/27424-h.htm</a>."
}
}