FFmpeg: RGB affected luma cycle

Utilising the 'extractplanes', 'blend', and 'xfade' filters found in FFmpeg 4.2.2. In the examples shown here, the following script and arguments were run (in order):
$ rgbLumaBlendCycle_FFmpeg.sh 'image1.jpg' 'screen'
$ rgbLumaBlendCycle_FFmpeg.sh 'image2.jpg' 'difference'
$ rgbLumaBlendCycle_FFmpeg.sh 'image3.jpg' 'pinlight' 'REV'

#!/usr/bin/env bash
# FFmpeg ver. 4.2.2+

# RGB affected luma cycle: Each colour plane is extracted and blended with the
# original image to adjust overall image brightness. The result of each blend
# is faded into the next, before belnding back to the original image.

# Parameters:
# $1 : Filename
# $2 : Blend type (e.g. average, screen, difference, pinlight, etc.)
# $3 : Reverse blend order (any string to enable)

# version: 2020.07.15_12.28.31
# source: https://oioiiooixiii.blogspot.com

function main()
{
   local mode="$2"
   local name="$1"
   local layerArr=('[a][colour1]' '[b][colour2]' '[c][colour3]'
                   '[colour1][a]' '[colour2][b]' '[colour3][c]')
   local layerIndex="${3:+3}" && layerIndex="${layerIndex:-0}"
   # Array contains values for both blend orders; index is offset if $3 is set

   ffmpeg \
      -i "$name" \
      -filter_complex "
         format=rgba,loop=loop=24:size=1:start=0,
            split=8 [rL][gL][bL][colour1][colour2][colour3][o][o1];
         [rL]extractplanes=r,format=rgba[a];
         [gL]extractplanes=g,format=rgba[b];
         [bL]extractplanes=b,format=rgba[c];
         ${layerArr[layerIndex++]}blend=all_mode=${mode}[a];
         ${layerArr[layerIndex++]}blend=all_mode=${mode}[b];
         ${layerArr[layerIndex]}blend=all_mode=${mode}[c];
         [o][a]xfade=transition=fade:duration=0.50:offset=0,format=rgba[a];
         [a][b]xfade=transition=fade:duration=0.50:offset=0.51,format=rgba[b];
         [b][c]xfade=transition=fade:duration=0.50:offset=1.02,format=rgba[c];
         [c][o1]xfade=transition=fade:duration=0.50:offset=1.53,format=rgba
          " \
      ${name}-${mode}.mkv
}

main "$@"

download: rgbLumaBlendCycle_FFmpeg.sh


Image Credits:

Henry Huey - "Alice in Wonderland - MAD Productions 5Sep2018 hhj_6811"
Attribution-NonCommercial 2.0 Generic (CC BY-NC 2.0)
https://www.flickr.com/photos/henry_huey/43768692515/

Henry Huey - "Alice in Wonderland - MAD Productions 5Sep2018 hhj_6869"
Attribution-NonCommercial 2.0 Generic (CC BY-NC 2.0)
https://www.flickr.com/photos/henry_huey/29740096427/

Henry Huey - "Alice in Wonderland - MAD Productions 5Sep2018 hhj_6848"
Attribution-NonCommercial 2.0 Generic (CC BY-NC 2.0)
https://www.flickr.com/photos/henry_huey/29740096117/