Improved finding new photos and converting them to lower-res version

Was not working well at all before.
Forums online suggested not using for-loop for this kind of job,
so I've replaced those with find -exec statements. Initial tests
suggest this is much more robust. Also fewer lines.

chertex.sh

@@ -193,44 +193,23 @@ if [ $# -eq 1 ]; then
          rsync -av "$path_thesis/assets/photos/" "$path_thesis/assets/photos/.lowres/" --exclude ".lowres/"
          touch "$photoslastrun"
       fi
-      # cd and use --parents arg to preserve directory structure in .lowres target
+      # Detect new photos and copy them into .lowres tree
+      # https://stackoverflow.com/questions/9612090/how-to-loop-through-file-names-returned-by-find
+      # https://stackoverflow.com/questions/5241625/find-and-copy-files
       cd "$path_thesis/assets/photos"
-      newphotos="$(find . -type f -cnewer $photoslastrun ! -path './.lowres/*')"
-      if [ -n "$newphotos" ]; then
-         for newphoto in $newphotos; do
-            cp --parents $newphoto .lowres/
-         done
-      fi
+      find . -type f -cnewer $photoslastrun ! -path "./.lowres/*" -print -exec cp --parents "{}" .lowres \;
       # revert the effects of cd above. Redirect to null suppresses the output.
       cd - >/dev/null
-      # in the low-res tree, find any photo larger than specific size (500kB)
-      largephotos="$(find $path_thesis/assets/photos/.lowres/ -size +500k)"
-      for largephotofilename in $largephotos; do
-         # for the next statement to work reliably, we should probably convert other formats to JPEG
-         # detect file extension, and based on it, convert to jpg using mogrify
-         largephotobase=$(basename -- "$largephotofilename") # just the filename (with extension, sans parents)
-         largephototype=${largephotobase#*.} # file extension only
-         largephotoname=${largephotofilename%.*} # path without extension
-         largephotobasename=${largephotobase%.*} # basename without extension
-         # some filetypes don't fare well when converted to jpeg, so we will only run the 
-         # forced conversion and shrinking unless the file extension is one of the following:
-         # "" (empty string, ie no file extension)
-         # SVG
-         # PDF
-         if [ ! "$largephototype" == "" ] || [ ! "$largephototype" == "svg" ] || [ ! "$largephototype" == "SVG" ] || [ ! "$largephototype" == "pdf" ] || [ ! "$largephototype" == "PDF" ]; then
-            # if the photo is not already jpeg, convert it to jpeg
-            if [ ! "$largephototype" == "jpg" ] && [ ! "$largephototype" == "jpeg" ] && [ ! "$largephototype" == "JPG" ] && [ ! "$largephototype" == "JPEG" ]; then
-               echo "<thesis> Converting $largephotobase to JPG format"
-               mogrify -format jpg $largephotofilename
-               # remove the now unnecessary non-jpg file from .lowres/
-               rm "$largephotofilename"
-            fi
-            # convert photo in-place (overwrite) with new one roughly 300kb in size
+      # Convert all non-JPG images (except for PDF, SVG, and other non-images) to JPG
+      echo "<thesis> Convert all non-JPG images to JPG"
+      find "$path_thesis/assets/photos/.lowres/" -type f ! -name "*.pdf" ! -name "*.svg" ! -name "*.external" ! -name "lastrun" ! -name "*.jpg" -print -exec mogrify -format jpg "{}" \;
+      # Remove the now redundant non-JPG files in .lowres/
+      echo "<thesis> Delete the redundant non-JPG files in .lowres/ tree"
+      find "$path_thesis/assets/photos/.lowres/" -type f ! -name "*.pdf" ! -name "*.svg" ! -name "*.external" ! -name "lastrun" ! -name "*.jpg" -print -exec rm "{}" \;
+      # Shrink image filesize in-place to roughly 300kb in size
+      echo "<thesis> Shrink images in .lowres/ tree to <=300K"
       # https://stackoverflow.com/questions/6917219/imagemagick-scale-jpeg-image-with-a-maximum-file-size
-            echo "<thesis> Shrinking $largephotobasename.jpg"
-            convert $largephotoname.jpg -define jpeg:extent=300kb $largephotoname.jpg
-         fi
-      done
+      find "$path_thesis/assets/photos/.lowres/" -size +500k -type f -name "*.jpg" -print -exec convert "{}" -define jpeg:extent=300kb "{}" \;
       # update the modification and access time on the photosastrun file
       touch "$photoslastrun"