TNGen: Thumbnail generator

Current version
v0.9.7 [en], [de], 2012-01-25
Download tngen-0.9.7-setup.exe (763KB).
TNGen is a simple, free thumbnail generator. You can specify a directory that is being scanned for JPEG files. Those are read and converted to thumbnails which you can save afterwards. TNGen also creates an HTML file with a thumbnail gallery as well as HTML files for a slide show, if you like.
Operating systems
Windows. Should run on any flavour of Windows.
TNGen is freeware that comes without any warranty or support. Thus you use it entirely at your own risk.

The setup file contains the TNGen executable and a small help file along with a template for slide shows. You can select a directory or use drag’n’drop from the explorer to drag a directory to the programme (although it is always the whole directory that is read).

The purpose of TNGen is to provide a simple interface to creating thumbnails. As a logical consequence, it can create image galleries and slide shows alike.

Usage is quite straight forward:

  1. Have TNGen read JPG files from a directory
  2. Specify a maximum width and/or height for the thumbnails
  3. Optionally confine the sizes of the original images as well
  4. Save the thumbs

Of course, you can determine the output of the gallery page or the slide show files. But the shipped defaults should suffice as starting point and do for most purposes.


  • HTML output only implemented: Only have TNGen recreate the HTML files. That’s useful when you simply changed the template code (before exiting the program).
  • Sort by EXIF information (dates), file size, file name
  • Remember sort order and status by prefixing the file names with numbers (Ctrl+Shift+O)
  • fix size of thumbs and images
  • copy EXIF information to thumbs
  • localized version (English, German)
  • command line interface for batch mode
  • Read and write JPEG comments (to the resulting files)
  • Slide show creation
  • Resample algorithms introduced: Better quality of thumbnails. Implemented by Anders Melander. (As Anders’ domain seems to be completely dead, I decided to offer his RESAMPLE.PAS for download from my server).
  • You can use an external application to rotate and view images. Resampling/Resizing can be done that way as well, if you are not pleased with the implemented resampling algorithms. I do not recommend that, as several features do not (automatically) work with external programmes!
  • Reordering of images is possible (although not saved between sessions)
  • Specify maximum dimensions for the thumbnails and/or original images:
    Set a maximum width and/or maximum height. The thumbnails will be scaled proportionally
  • Save thumbnails with the original filename plus a user specified suffix or prefix:
    The thumbnail for image.jpg will be named image_th.jpg, for instance
  • Generates configurable HTML output and can create a directory with thumbs, images and an HTML file
  • HTML profiles: You can create several HTML profiles to quickly change the code for galleries
  • Display information about images and thumbs in a list
  • Process only selected files
  • Resize the original images when saving the files:
    This also allows specification of maximum width and/or height
  • Renaming files


v0.9.7 — 2009-09-08

  • Time adaptation of thumbs
  • Basic caching of unmodified thumbs
  • Small bug fixes

v0.9.6 — 2008-08-18

  • Bugfixes in language handlings
  • Bugfix with slide show numbering
  • Bugfix with HTML output only not calculating dimensions properly
  • Picture names can be used in the slide file names
  • Shipped new slide show example file
  • New option –ini-file specifies which ini file to load
  • Slide show file name prefix and index file name can be chosen

v0.9.5 — 2007-06-10

Again mostly a bugfix and polishing build

  • Several small usability fixes on the UI
  • Different behaviour with deactivated thumbs and possibility to hide them in the preview
  • Save option: Write thumbs only (do not touch originals)
  • copy HTML profile to a new one
  • Refresh the whole list: Check if some original files have changed and refresh them if necessary. Does not load new images or remove deleted ones. Useful when you — while you’re working on the thumbnails — notice that one image could use some touching up.

v0.9.4 — 2007-05-31

This is mainly a bugfix and enhancement release for existing features.

  • enhanced command line interface: logfile, loglevel, create-empty, no-create-output-dir, minimized. Refer to the documentation.
  • Possibility to specify an absolute path as output directory. Non-xisting directories on the output path are now created.
  • HTML output only.
  • Remember the stati of the check boxes for size constraints.
  • New variables for managing the JPEG comments. See documentation.

v0.9.3 — 2007-05-06

  • implemented option to (not) encode HTML entities from image comments. This allows for using HTML code in image comments.
  • implemented sorting by dates, name and size
  • Possibility to store the order and status of files by prefixing the file names with some information. You can also remove these prefixes again. See menu Edit
  • enable replacing of variables in slide shows. You can now use $$COMMENT$$ there as well, for instance
  • changed replacement of CR LF to not use commas but simple blanks to separate lines
  • implemented a little bit of intelligence when renaming files

v0.9.2 — 2007-03-09

  • Updated dEXIF to 1.03 which fixes some bugs with handling EXIF data
  • Introduced option to copy EXIF information to originals and thumbs
  • Introduced variable $$PICTURENAME$$ for the image file name without extension
  • Introduced Edit > Remove inactive images from the list which is useful after generating a gallery, after toggling the selection.
  • Possibility to fix the sizes of original images and thumbs. Creates borders.
  • Bug fixes:
    • Preferences: properly edit multiline comments
    • Focus fixes
    • F1 now actually launches help
    • fixed focus bug when clicking on a thumb and having the HTML page activated
    • layout fixes in preferences dialogue
    • fixed an error message
    • fixed a bug with constraining thumbs
    • fixed reading problem with write protected files
    • fixed scrolling issue in the thumb preview

v0.9.1 — 2006-09-20

  • Alt+P changed to Ctrl+F12
  • Bugfix with handling comments. Thanks to Tony Paskell for the discovery
  • potential danger fix: HTMLEntityEncode for Comments implemented
  • Multiline comments: replace #13#10 with ,
  • reload thumb from disk. Useful when you launch a viewer and modifiy the image.
  • Some UI polish:
    • Trying out a new icon
    • The thumbnail preview adapts a little bit to the specified maximal width constraint
    • And some more, including work on the menus and tabbing order

    v0.9 — 2006-09-14

    • Internationalization and localization: TNGen can now be translated. German and English are available. If anyone wants to translate TNGen, contact me.
    • Command line interface. See help for details
    • fixed bug with slide show: template was not assigned properly before launching preferences
    • added warning for unreadable/corrupted files
    • New variables for HTML files to enable URL-encoded names for non-alphanumeric characters

    v0.8.1 — 2005-10-22 (bugfix release)

    • I now ship a working help file.
    • I had an ugly bug when using a slideshow without an existing slideshow template.

    v0.8 — 2005-08-25

    • Ctrl+C and Ctrl+P changed to Alt+C/P
    • Preferences for prefix/suffix now applied when saving, not when generating
    • Saving of files now properly treats the “lower case” setting
    • Bugfix: Wrong counting when saving images and wrong focus fixed
    • Bugfix: Scrolling thumbs was erroneous
    • Fixed tab order in main UI and preferences
    • Introduced lossless JPEG rotation and preference to not use IMP
    • Introduced option to not save thumbs but modifiy originals only.
    • Warning when generating a new list
    • Save comments also to original files

    v0.7 — 2005-03-17

    • Bugfix: Error with only one image in the directory
    • Bugfix: Overwriting of destination file failed in some instances with external programmes
    • Possibility to read and write JPEG comments
    • Quicker toggling of images in the thumb list by right clicking the file
    • No file extension necessary any more. I now read all JPEG files.

    v0.6 — 2004-09-24

    • Incorporated slide shows into HTML profiles (changes in preferences, thus a new version)
    • Improved keyboard handling (Ctrl+CursorKeys or Ctrl+scroll wheel now swap images)
    • ignoring inactive thumbs when reordering

    v0.5 — 2004-09-23

    • Reordering of images implemented
    • Slide shows
    • Resampling filters implemented
    • Use of an external application is now possible (rotation, resampling)