bash_snippets/README.md

# Collection of Bash code snippets, mostly one liners, to ease file handling among other things
Collection of notes
#### rename files to reverse order

`N=1; ls -tr -1 *.jpg | tac | while read file; do mv "$file" "$N".jpg; N=$((N+1)); done`  

#### rotate all images using imagemagick

`mogrify -rotate 180 *.jpg`  
`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
```