Scripts for making photos in to lofi pixel art

gradientify.sh

#!/bin/bash                                                                                                 
# based on cellusion's photoshop method                                                                     
convert "$1" -resize 256x1000  -colorspace Gray -auto-level \                                               
    gradient.png -clut -scale 1000x1000 -posterize 6 "$1".out.png

make-gradient.sh

#!/bin/bash                                                                                                 
# based on cellusion's photoshop method                                                                     
                                                                                                            
# make the gradient                                                                                         
                                                                                                            
function gradient-step() {                                                                                  
  left=$1                                                                                                   
  right=$2                                                                                                  
  width=$(( $3 * 256 ))                                                                                     
  convert \( -size 1x1 "xc:$left" "xc:$right" +append \) \                                                  
      -filter cubic -resize ${width}x1! grad.png                                                            
  if [ -e gradient.png ]; then                                                                              
      convert gradient.png grad.png +append tmp.png                                                         
      mv tmp.png gradient.png                                                                               
      rm grad.png                                                                                           
  else                                                                                                      
      mv grad.png gradient.png                                                                              
  fi                                                                                                        
}                                                                                                           
                                                                                                            
function finalize-gradient() {                                                                              
    convert gradient.png -resize 256x1! tmp.png                                                             
    mv tmp.png gradient.png                                                                                 
}                                                                                                           
                                                                                                            
rm -f gradient.png                                                                                          
                                                                                                            
#gradient-step black orange 30                                                                              
#gradient-step orange pink 30                                                                               
#gradient-step pink white 10                                                                                
#gradient-step white lime 10                                                                                
                                                                                                            
#gradient-step black orange 30                                                                              
#gradient-step orange pink 30                                                                               
#gradient-step pink white 10                                                                                
#gradient-step white lime 10                                                                                
                                                                                                            
gradient-step black cyan 70                                                                                 
gradient-step cyan white 10                                                                                 
gradient-step white yellow 20                                                                               
gradient-step yellow maroon1 10                                                                             
                                                                                                            
#gradient-step black red 5                                                                                  
#gradient-step red black 2                                                                                  
#gradient-step black maroon1 70                                                                             
#gradient-step maroon1 white 10                                                                             
#gradient-step white cyan 15                                                                                
                                                                                                            
finalize-gradient

This seems exciting! (I found you through your translation of the Japanese game designer's post, through Hacker News.)
How do you use this? I tried bash gradientify.sh <image>, but I need a gradient.png. Could you provide the one you use? Or am I misunderstanding how to use this?