How to fix tumbler-folder-thumbnailer and show custom folder icons on Thunar

If you installed tumbler-folder-thumbnailer alongside ImageMagick and Inkscape but your custom folder thumbnails (like .folder.png) are still not appearing in your file manager (like Thunar), you are likely running into an ImageMagick v7 syntax error and a stuck thumbnail cache.

1. Open your terminal and edit the script with administrative privileges: sudo vim /usr/bin/folder-thumbnailer
2. Update the script to place the file paths before the -thumbnail command. Here is the corrected script that handles .jpg, .png, and .svg (using Inkscape). This is a modified script that makes icons not anti-aliased, preserving pixels:

#!/bin/bash

$1=size,$2 = input folder, $3=outputthumbnailfile,$4 = URI

Generate the MD5 hash for the cache clearing fallback

MD5_HASH=$(echo-n"$4” | md5sum | cut -d ” ” -f1)

if [ -f “2/.folder.jpg" ]; then # For JPEGs: Use Lanczos to ensure high-quality, smooth downscaling for photos magick "2/.folder.jpg” -filter Lanczos -resize “$1x$1” -strip “$3” 1>/dev/null 2>&1

elif [ -f “2/.folder.png" ]; then # For PNGs: Use 'point' filter to disable anti-aliasing interpolation. # This keeps pixel art and 32x32 icons razor sharp with hard grid edges! magick "2/.folder.png” -filter point -resize “$1x$1” -background none -gravity center -strip “$3” 1>/dev/null 2>&1

elif [ -f “2/.folder.svg" ]; then # For SVGs: Convert SVG to temporary PNG using Inkscape inkscape --export-type=png --export-dpi=500 "2/.folder.svg” —export-filename=“3" 1>/dev/null 2>&1 # Scale that PNG down using point filter to keep the vector lines super sharp magick "3” -filter point -resize “$1x$1” -strip “$3” 1>/dev/null 2>&1

else # If no custom image is found, clear any old custom cached thumbnails rm -f “$HOME/.cache/thumbnails/normal/${MD5_HASH}.png”
“$HOME/.thumbnails/normal/${MD5_HASH}.png”
“$HOME/.cache/thumbnails/large/${MD5_HASH}.png”
“$HOME/.thumbnails/large/${MD5_HASH}.png” 2>/dev/null fi

3. Make sure that both the script and the configuration files are reachable and executable by the system
`sudo chmod +x /usr/bin/folder-thumbnailer`
4. Reset the cache and service
`rm -rf ~/.cache/thumbnails/* && rm -rf ~/.thumbnails/* && thunar -q && killall tumblerd`

To trigger the script on any folder, simply drop an image inside it named exactly `.folder.png`, `.folder.jpg`, or `.folder.svg`