I got hundreds of old files (some are from 2.4x) that need to generate Preview/thumbnail images with the new Blender version. I think the straightforward way is to open and save each files to generate, which is quite inefficient. So I'm wondering a quicker way to do this automatically. (via a command line or bat file?)


2 Answers 2


Thumbnail extraction via Python

The most current thumbnailer is maintained by ideasman42:


It extracts thumbnail that is stored in a blend file for use with a file manager.

Usage: blender-thumbnailer.py <input.blend> <output.png>


python blender-thumbnailer.py test.blend test.png

Batch rendering via command line

Alternatively you could batch process the .blend files from a .bat file:

for %%f in (*.blend) do (
            blender %%~nf.blend -b -o //%%~nf -F PNG -x 1 -f 1

See also the documentation of command line parameters.

In order to set a fixed thumbnail size you would (probably) invoke a python script (-P script_name.py) that sets the render size.

Something like this size.py (didn't work for me):

import bpy  

bpy.data.scenes[0].render.resolution_x = 128
bpy.data.scenes[0].render.resolution_y = 128
bpy.data.scenes[0].render.resolution_percentage = 100

In Blenders installation directory is a file "BlendThumb64.dll" which is registered during installation or

C:\Program Files\Blender Foundation\Blender>blender -R
Registering file extension...success (user)

Running as administrator would register .blend for all users.

I'm not sure whether this is related: In C:\Users\<username>\.thumbnails\normal and C:\Users\<username>\.thumbnails\fail\blender you can find created (or failed) thumbnails.

Load, render and save

import bpy
import os

filepath = bpy.data.filepath
directory = os.path.dirname(filepath)
image_path = os.path.join( directory , "image.png")
bpy.data.scenes['Scene'].render.filepath = image_path
bpy.ops.render.render( write_still=True ) 
print("file %s" % filepath )

blender -b test.blend -P save.py (above script, didn't recreate the embedded thumbnail)

  • $\begingroup$ Thanks stacker, I see your code is working. Actually, The word "thumbnail" I mean is the "thumb icon" for .blend itself, like this. $\endgroup$ Jan 16, 2015 at 10:40
  • $\begingroup$ I didn't figure out how to use the blender-thumbnailer.py and I'm not sure if it meets my need here. Could you tell more about it? $\endgroup$ Jan 17, 2015 at 3:24
  • $\begingroup$ @LeonCheung the blender-thumbnailer.py only extracts a png from .blend, saving a loaded file recreates the thumbnail, my last try was to automate this with a script but it didn't recreate the thumbnail. Sorry $\endgroup$
    – stacker
    Jan 17, 2015 at 9:32
  • $\begingroup$ It's OK. Thanks all the same for the nice answer though. It's very inspiring. :) $\endgroup$ Jan 17, 2015 at 10:10

Inspired by stacker's answer:

I built two files, one is a save_prev.py file:

import bpy


Another one is a .bat file:

for %%f in (*.blend) do (
      <blender_install_path> %%~nf.blend -P save_prev.py

For example, if I installed the official Blender (for Windows) all by default, then it may be like this:

for %%f in (*.blend) do (
      C:\PROGRA~1\BLENDE~1\Blender\blender %%~nf.blend -P save_prev.py

Then, put these two files into the same folder containing all the old files, run .bat.

I found that -b parameter appears not working in this case. That is why I have to open, save and close each file by a separate save_prev.py. Not so effective, I know, but it saves a lot of manual work more or less.

The result is exactly what I want, but I still appreciate any better idea to do this.

  • $\begingroup$ have you tried to supply '-b' as the first parameter, Blender appears to be picky on parameter order. $\endgroup$
    – stacker
    Jan 17, 2015 at 9:35
  • $\begingroup$ Yes, I tried to tweak with orders, too. :( And btw, my way got a big disadvange. It cannot operate on those files with space in their filenames. I don't know why yet. $\endgroup$ Jan 17, 2015 at 10:08

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.