source = "one/3.1-3.4-_v-_and_w-Knots,_the_Basics.pdf";
target = "Handout-120222.png";
If[FileType[target] === None ||
    AbsoluteTime[FileDate[source]] > AbsoluteTime[FileDate[target]],
  command = "convert -density 300 -background white -alpha Flatten "<>source<>" "<>target;
  Print["Running "<>command<>" ..."];
  Run[command];
];
target = "Handout-120222_400.jpg";
If[FileType[target] === None ||
    AbsoluteTime[FileDate[source]] > AbsoluteTime[FileDate[target]],
  command = "convert -geometry 400x400 -gamma 0.45 -background white -alpha Flatten "<>source<>" "<>target;
  Print["Running "<>command<>" ..."];
  Run[command];
];

source = "one/Terrific_Pictures_by_Shin_Satoh.pdf";
target = "Terrific_Pictures_by_Shin_Satoh.png";
If[FileType[target] === None ||
    AbsoluteTime[FileDate[source]] > AbsoluteTime[FileDate[target]],
  command = "convert -density 300 -background white -alpha Flatten "<>source<>" "<>target;
  Print["Running "<>command<>" ..."];
  Run[command];
];
target = "Terrific_Pictures_by_Shin_Satoh_400.jpg";
If[FileType[target] === None ||
    AbsoluteTime[FileDate[source]] > AbsoluteTime[FileDate[target]],
  command = "convert -geometry 400x400 -gamma 0.45 -background white -alpha Flatten "<>source<>" "<>target;
  Print["Running "<>command<>" ..."];
  Run[command];
];

source = "one/Handout_for_April_18_and_25.pdf";
target = "Handout_for_April_18_and_25.png";
If[FileType[target] === None ||
    AbsoluteTime[FileDate[source]] > AbsoluteTime[FileDate[target]],
  command = "convert -density 300 -background white -alpha Flatten "<>source<>" "<>target;
  Print["Running "<>command<>" ..."];
  Run[command];
];
target = "Handout_for_April_18_and_25_400.jpg";
If[FileType[target] === None ||
    AbsoluteTime[FileDate[source]] > AbsoluteTime[FileDate[target]],
  command = "convert -geometry 400x400 -gamma 0.45 -background white -alpha Flatten "<>source<>" "<>target;
  Print["Running "<>command<>" ..."];
  Run[command];
];
