Thumbnails

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Enabling Thumbnailers

On minimal / custom desktop environments thumbnails in file explorers may not work by default. For example:

• GNOME environments with the option services.gnome.core-utilities.enable = false;
• Custom environments built from ground-up using window managers like sway or hyperland

Save yourself hours of troubleshooting!!

Thumbnailers may already be installed in your system as dependencies of image/video applications but are not activated.

Run cd /run/current-system/sw/share/thumbnailers && ls to list installed thumbnailers. If relevant .thumbnailer files are present and we still don't have thumbnails in our file explorer then we may need to activate them by updating symlinks to share/thumbnailers

# configuration.nix
{

  environment.pathsToLink = [
    "share/thumbnailers"
  ];

}

Enable Video Thumbnails

To enable thumbnails for video files use ffmpeg-headless to decode videos and fmpegthumbnailer to generate thumbnails.

Thumbnails for the following MimeTypes are enabled: video/jpeg; video/mp4; video/mpeg; video/quicktime; video/x-ms-asf; video/x-ms-wm; video/x-ms-wmv; video/x-ms-asx; video/x-ms-wmx; video/x-ms-wvx; video/x-msvideo; video/x-flv; video/x-matroska; application/x-matroska; application/mxf; video/3gp; video/3gpp; video/dv; video/divx; video/fli; video/flv; video/mp2t; video/mp4v-es; video/msvideo; video/ogg; video/vivo; video/vnd.avi; video/vnd.divx; video/vnd.mpegurl; video/vnd.rn-realvideo; application/vnd.rn-realmedia; video/vnd.vivo; video/webm; video/x-anim; video/x-avi; video/x-flc; video/x-fli; video/x-flic; video/x-m4v; video/x-mpeg; video/x-mpeg2; video/x-nsv; video/x-ogm+ogg; video/x-theora+ogg.

# configuration.nix
{ pkgs, ... }: 
{

  environment.systemPackages = with pkgs; [
    ffmpeg-headless
    ffmpegthumbnailer
  ];

  # 'ffmpegthumbnailer.thumbnailer' is created in '/run/current-system/sw/share/thumbnailers'

}

Enable Image Thumbnails

To enable thumbnails for image files use gdk-pixbuf to decode images and generate thumbnails.

Thumbnails for the following MimeTypes are enabled: image/png; image/jpeg; image/bmp; image/x-bmp; image/x-MS-bmp; image/gif; image/x-icon; image/x-ico; image/x-win-bitmap; image/vnd.microsoft.icon; application/ico; image/ico; image/icon; text/ico; image/x-portable-anymap; image/x-portable-bitmap; image/x-portable-graymap; image/x-portable-pixmap; image/tiff; image/x-xpixmap; image/x-xbitmap; image/x-tga; image/x-icns; image/x-quicktime; image/qtif.

# configuration.nix
{ pkgs, ... }: 
{

  environment.systemPackages = with pkgs; [ 
    gdk-pixbuf
  ];

  # 'gdk-pixbuf-thumbnailer.thumbnailer' is created in '/run/current-system/sw/share/thumbnailers'

}

Enable HEIF Image Thumbnails

To enable thumbnails for HEIF image format use libheif to decode HEIF images and libheif.out to generate thumbnails.

Thumbnails for the following MimeTypes are enabled: image/heif; image/avif.

# configuration.nix
{ pkgs, ... }: 
{

  environment.systemPackages = with pkgs; [ 
    libheif
    libheif.out
  ];

  # 'heif.thumbnailer' is created in '/run/current-system/sw/share/thumbnailers'

}

Enable RAW (Camera) Image Thumbnails

nufraw-thumbnailer

To enable thumbnails for camera RAW format use nufraw to decode RAW images and nufraw-thumbnailer to generate thumbnails.

Thumbnails for the following MimeTypes are enabled: image/x-canon-cr2;image/x-canon-crw;image/x-minolta-mrw;image/x-nikon-nef;image/x-pentax-pef;image/x-panasonic-rw2;image/x-panasonic-raw2;image/x-samsung-srw;image/x-olympus-orf;image/x-sony-arw.

# configuration.nix
{ pkgs, ... }: 
{

  environment.systemPackages = with pkgs; [ 
    nufraw
    nufraw-thumbnailer
  ];

  # 'nufraw.thumbnailer' is created in '/run/current-system/sw/share/thumbnailers' 

}

nufraw-thumbnailer

• creates thumbnails using the embedded 'jpeg' in the camera raw files. ( --noexif )
• does not respect the EXIF metadata. ( --embedded-image )

Output of cat /run/current-system/sw/share/thumbnailers/nufraw.thumbnailer:

[Thumbnailer Entry]
TryExec=/nix/store/piss9dl8i5xnfm5yagdffgxycm8lsqpl-nufraw-0.43-3/bin/nufraw-batch
Exec=/nix/store/piss9dl8i5xnfm5yagdffgxycm8lsqpl-nufraw-0.43-3/bin/nufraw-batch --silent --size %s --out-type=png --noexif --output=%o --embedded-image %i
MimeType=image/x-canon-cr2;image/x-canon-crw;image/x-minolta-mrw;image/x-nikon-nef;image/x-pentax-pef;image/x-panasonic-rw2;image/x-panasonic-raw2;image/x-samsung-srw;image/x-olympus-orf;image/x-sony-arw

Additional cameras beyond those listed in the stock nufraw.thumbnailer file are also supported. The following additional MimeTypes are supported: image/x-adobe-dng; image/x-dcraw; image/x-fuji-raf; image/x-kodak-dcr; image/x-kodak-k25; image/x-kodak-kdc; image/x-nikon-nrw; image/x-panasonic-raw; image/x-sigma-x3f; image/x-sony-srf; image/x-sony-sr2

Eg: Generate thumbnails from 'raw' data (not 'embedded jpeg') + respect EXIF (eg: rotation) metadata + add support for additional camera formats

# configuration.nix
{ pkgs, ... }:

{

  environment.systemPackages = [
    nufraw
    nufraw-thumbnailer
    # Thumbnails form 'raw' data and include EXIF tags for Adobe-DNG images
    (writeTextDir "share/thumbnailers/my-custom-nufraw.thumbnailer" ''
      [Thumbnailer Entry]
      TryExec=nufraw-batch
      Exec=nufraw-batch --silent --size %s --out-type=png --output=%o %i
      MimeType=image/x-adobe-dng;image/x-dng;
    '';)
    # MimeTypes not listed here but listed in the default nufraw.thumbnailer will continue displaying
      # thumbnails generated form the 'embedded jpeg' without the EXIF metadata
  ];

}

gdk-pixbuf thumbnailer

The gdk-pixbuf thumbnailer can also generate thumbnails (from 'embedded jpeg') for RAW camera image formats. It cannot decode 'raw' image data but can read the 'embedded jpeg'.

# configuration.nix
{ pkgs, ... }:

{

  environment.systemPackages = [
    gdk-pixbuf
    (writeTextDir "share/thumbnailers/my-custom-nufraw.thumbnailer" ''
      [Thumbnailer Entry]
      TryExec=gdk-pixbuf-thumbnailer
      Exec=gdk-pixbuf-thumbnailer -s %s %u %o
      MimeType=image/x-adobe-dng;image/x-dng;image/x-canon-cr2;image/x-canon-crw;image/x-cr2;image/x-crw;
    '';)
  ];

}

Creating Custom Thumbnailers

Most package mangers accept the Thumbnail Managing Standard, by using it you can create your own thumbnailer for any file format, this can be done by:

1. First you need to figure out how to create a .png image from a file in the desired format.
2. Create a .thumbnailer file in $XDG_DATA_DIRS/thumbnailers.
3. Restart your thumbnailer service (This is specific to each file manager) and test if it's working.

Example

You could create a thumbnailer for Krita's .kra file format like so:

.kra are zip files, with a preview stored at /preview.png, we can use unzip to extract the preview:

unzip -p robot-squirrel.kra preview.png > robot-squirrel.png

Create a .thumbnailer file in any $XDG_DATA_DIRS/thumbnailers directory.

# $HOME/.local/share/thumbnailers/kra.thumbnailer
[Thumbnailer Entry]
Exec=sh -c "unzip -p %i preview.png > %o"
MimeType=application/x-krita;

Restart your thumbnailer service (This is specific to each file manager) and test if it's working.

After you have a working definition, you can make it reproducible like so:

# configuration.nix
{ pkgs, ... }: {
  environment.systemPackages = [
    (
      pkgs.writeTextFile {
        # This can be anything, it's just the name of the derivation in the nix store
        name = "krita-thumbnailer";
        # This is the important part, the path under which this will be installed
        destination = "/share/thumbnailers/kra.thumbnailer";
        # The contents of your thumbnailer, don't forget to specify the full path to executables
        text = ''
          [Thumbnailer Entry]
          Exec=sh -c "${pkgs.unzip}/bin/unzip -p %i preview.png > %o"
          MimeType=application/x-krita;
        '';
      }
    )
  ];
}