This script creates web files in the current directory

create_webp_files.sh

#!/bin/bash

# converting JPEG images
find . -type f -and \( -iname "*.jpg" -o -iname "*.jpeg" \) -exec bash -c '
  for result; do
    webp_path=$(sed '\''s/\.[^.]*$/.webp/'\'' <<< "$result");
    if [ ! -f "$webp_path" ]; then 
      cwebp "$result" -o "$webp_path";
    fi;
  done
' _ {} +

# converting PNG images
find . -type f -and -iname "*.png" -exec bash -c '
  for result; do
    webp_path=$(sed '\''s/\.[^.]*$/.webp/'\'' <<< "$result");
    if [ ! -f "$webp_path" ]; then 
      cwebp -lossless "$result" -o "$webp_path";
    fi;
  done
' _ {} +

# converting GIF
find . -type f -and -iname "*.gif" -exec bash -c '
  for result; do
    webp_path=$(sed '\''s/\.[^.]*$/.webp/'\'' <<< "$result");
    if [ ! -f "$webp_path" ]; then 
      gif2webp "$result" -mixed -o "$webp_path";
    fi;
  done
' _ {} +