__init__.py

# ##### BEGIN GPL LICENSE BLOCK #####
#
#  This program is free software; you can redistribute it and/or
#  modify it under the terms of the GNU General Public License
#  as published by the Free Software Foundation; either version 2
#  of the License, or (at your option) any later version.
#
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#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
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#  along with this program; if not, write to the Free Software Foundation,
#  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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# ##### END GPL LICENSE BLOCK #####

# <pep8-80 compliant>

bl_info = {
    "name": "Preview Addon",
    "author": "Nathan Craddock",
    "version": (1, 0, 0),
    "blender": (2, 76, 0),
    "location": "Object panel",
    "description": "Just a test",
    "warning": "",
    "category": "Object"
}

if "bpy" in locals():
    import importlib
    importlib.reload(Previews)
else:
	from . import Previews
    
import bpy
	
def register():	
    bpy.utils.register_module(__name__)
    Previews.register()


def unregister():
    bpy.utils.unregister_module(__name__)
    Previews.unregister()


if __name__ == "__main__":
    register()

Previews.py

import bpy
from bpy.types import Panel, EnumProperty, WindowManager
import bpy.utils.previews

import os

# UI
class PreviewsExamplePanel(bpy.types.Panel):
    bl_label = "Previews Example Panel"
    bl_idname = "OBJECT_PT_previews"
    bl_space_type = 'PROPERTIES'
    bl_region_type = 'WINDOW'
    bl_context = "object"

    def draw(self, context):
        layout = self.layout
        wm = context.window_manager
        row = layout.row()
        
        # This tells Blender to draw the my_previews window manager object
        # (Which is our preview)
        row.template_icon_view(context.scene, "my_thumbnails")
        
        # Just a way to access which one is selected
        row = layout.row()
        row.label(text="You selected: " + bpy.context.scene.my_thumbnails)


preview_collections = {}

def generate_previews():
    # We are accessing all of the information that we generated in the register function below
    pcoll = preview_collections["thumbnail_previews"]
    image_location = pcoll.images_location
    VALID_EXTENSIONS = ('.png', '.jpg', '.jpeg')
    
    enum_items = []
    
    # Generate the thumbnails
    for i, image in enumerate(os.listdir(image_location)):
        if image.endswith(VALID_EXTENSIONS):
            filepath = os.path.join(image_location, image)
            thumb = pcoll.load(filepath, filepath, 'IMAGE')
            enum_items.append((image, image, "", thumb.icon_id, i))
            
    return enum_items
    
def register():
    from bpy.types import Scene
    from bpy.props import StringProperty, EnumProperty
    
    # Create a new preview collection (only upon register)
    pcoll = bpy.utils.previews.new()
    
    # This line needs to be uncommented if you install as an addon
    pcoll.images_location = os.path.join(os.path.dirname(__file__), "images")
    
    # This line is for running as a script. Make sure images are in a folder called images in the same
    # location as the Blender file. Comment out if you install as an addon
    #pcoll.images_location = bpy.path.abspath('//images')
    
    # Enable access to our preview collection outside of this function
    preview_collections["thumbnail_previews"] = pcoll
    
    # This is an EnumProperty to hold all of the images
    # You really can save it anywhere in bpy.types.*  Just make sure the location makes sense
    bpy.types.Scene.my_thumbnails = EnumProperty(
        items=generate_previews(),
        )
    
def unregister():
    from bpy.types import WindowManager
    for pcoll in preview_collections.values():
        bpy.utils.previews.remove(pcoll)
    preview_collections.clear()
    
    del bpy.types.Scene.my_thumbnails
   
if __name__ == "__main__":
    register()

Thank you for the code! I have a question: what is the porpuse of the variable 'wm' in line 17?

Thank you for the code! I have a question: what is the porpuse of the variable 'wm' in line 17?

@mati23 wm stands for window manager. It appears though that I did not use the variable (I modified the code from the templates included with Blender). You do not need to make the wm variable.

Hello Nate, I'm trying to run te preview on the scripting enviorenment of blender and don't happen anything, look the error:

Exception ignored in: <function ImagePreviewCollection.__del__ at 0x000001CCFAB451F8> Traceback (most recent call last): File "D:\Program Files\Blender Foundation\Blender 2.82\2.82\scripts\modules\bpy\utils\previews.py", line 79, in __del__ f"{self!r}: left open, remove with " ResourceWarning: <ImagePreviewCollection id=0x1ccfb008588[0], <super: <class 'ImagePreviewCollection'>, <ImagePreviewCollection object>>>: left open, remove with 'bpy.utils.previews.remove()' Exception ignored in: <function ImagePreviewCollection.__del__ at 0x000001CCFAB451F8> Traceback (most recent call last): File "D:\Program Files\Blender Foundation\Blender 2.82\2.82\scripts\modules\bpy\utils\previews.py", line 79, in __del__ f"{self!r}: left open, remove with " ResourceWarning: <ImagePreviewCollection id=0x1ccfb008708[1], <super: <class 'ImagePreviewCollection'>, <ImagePreviewCollection object>>>: left open, remove with 'bpy.utils.previews.remove()'

@BETAPANDERETA this script was written many years ago, and things have changed in Blender 2.8x and above. I may update it eventually, but I don't have time to help debug right now :(

But Blender ships with example python templates, and there is one very similar to this one. In the Text Editor header choose Templates > Python > ui_previews_dynamic_enum.py. That should get you close :)

thankyou verymuch