Convert and Rescale Many Images Using FFMPEG

convert_and_resize.bat

:: FOR WINDOWS batch

: using for /f "tokens=*" %i in ('dir /aa /b /o-d')
for /f "tokens=*" %%i in ('dir /aa /b /o-d') do ffmpeg -i "%%i" -vf "scale=min'(2000,iw):-1'" "converted_jpg\%%~ni.jpg"

convert_and_resize.sh

#!/bin/bash 
##########################################################
# To convert and resize image files, basically:
### ffmpeg -i "INPUT FILE" -vf "scale=min'(2000,iw):-1'" "OUTPUT FILE"
# 
#  -i "INPUT FILE"
#      This is the input file parameter, specifying the location of the image you want to resize.
#
#  -vf "scale=min'(2000,iw):-1'" 
#      This resizes the image so that its longest side is 2000 pixels, while maintaining the aspect ratio `-1`. 
#      The min() function ensures that only images with a width of at least 2000 pixels are resized down, not up.
#      More details at https://ffmpeg.org/ffmpeg-filters.html#scale-1
#
#  "OUTPUT FILE"
#      This is where the resized image will be saved.
#
#
############################################################
# 
# Looping:
# There are two ways to loop through the files.
# 1) find . -maxdepth 1 -type f | while read i
# 2) ls -tp | grep -v / | while read i
#
##############################################################
### find . -maxdepth 1 -type f | while read i
# 
#  find . 
#      This command searches for files and directories.
#      The dot (.) means the current directory where your images are located.
#
#  -maxdepth 1
#      This limits the search to the current directory only, not subdirectories.
#
#  -type f
#      This filters the results to include only files, not directories.
#
#
###############################################################
### ls -tp | grep -v / | while read i
#
#  ls
#      This command lists the contents of the directory.
#  
#  -tp 
#      These are two options combined:
#      -t sorts the files by modified time.
#      -p adds a slash (/) to directories in the output.
#
#  grep -v /
#      This filters out directories from the `ls` output.
#      -v / excludes lines that contain a slash (/) from the output.
#
#
###############################################################
### while read i
#       This is a while loop that reads each file name into the variable `i`.
#
#
###############################################################
# About the ffmpeg command I will use:
#   $i
#       This is the current file name from the loop.
#
#   -i "$(basename "$i")"
#       This takes just the file name, excluding any leading `./`.
#
#   "converted_jpg/$(basename "${i%.*}.jpg")"
#       This specifies the output location. `converted_jpg` is a subdirectory you should create beforehand. 
#       "${i%.*}.jpg" changes the file extension to jpg.
#
#   < /dev/null 
#       This redirects input to `/dev/null`, making sure no input is passed to ffmpeg.
#       (Specifically needed for `ls`.) 
#
#
###############################################################
# Usage:

# Using find . -maxdepth 1 -type f
#  find . -maxdepth 1 -type f | while read i; do ffmpeg -i "$(basename "$i")" -vf "scale=min'(2000,iw):-1'" "converted_jpg/$(basename "${i%.*}.jpg")"; done

# Using ls -tp | grep -v /
ls -tp | grep -v / | while read i; do ffmpeg -i "$(basename "$i")" -vf "scale=min'(2000,iw):-1'" "converted_jpg/$(basename "${i%.*}.jpg")" </dev/null; done