added loop to do sth in each folder

README.md

@@ -7,3 +7,16 @@ Collection of notes
 ```mogrify``` overwrites existing images which is what makes it different from ```convert```
 #### cut poly-shape out of image, crop image to its boundaries, fill surrounding holes in certain color or transparent (for all jpgs in folder)
 ```for f in ./*.jpg; do convert "$f" \( -clone 0 -fill black -colorize 100 -fill white -draw "polygon 3276,2421 4945,2407 4956,4708 3287,4722" \) -alpha off -compose copy_opacity -composite -trim +repage 41050648/"$f"_left.jpg; done```
+#### do something inside each folder of this folder
+```
+for d in */; do
+  cd $d;
+  for dir in */; do
+    for frontpage in "$dir"*.jpg; do
+      echo convert "$frontpage" -resize 500x500 "$frontpage"_500px.jpg
+      break 1
+    done
+  done
+  cd ..;
+done
+```