blender/release/scripts/templates_py/ui_previews_custom_icon.py

# This sample script demonstrates how to place a custom icon on a button or
# menu entry.
#
# IMPORTANT NOTE: if you run this sample, there will be no icon in the button
# You need to replace the image path with a real existing one.
# For distributable scripts, it is recommended to place the icons inside the
# addon folder and access it relative to the py script file for portability
#
#
# Other use cases for UI-previews:
# - provide a fixed list of previews to select from
# - provide a dynamic list of preview (eg. calculated from reading a directory)
#
# For the above use cases, see the template 'ui_previews_dynamic_enum.py"


import os
import bpy


class PreviewsExamplePanel(bpy.types.Panel):
    """Creates a Panel in the Object properties window"""
    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
        pcoll = preview_collections["main"]

        row = layout.row()
        my_icon = pcoll["my_icon"]
        row.operator("render.render", icon_value=my_icon.icon_id)

        # my_icon.icon_id can be used in any UI function that accepts
        # icon_value # try also setting text=""
        # to get an icon only operator button


# We can store multiple preview collections here,
# however in this example we only store "main"
preview_collections = {}


def register():

    # Note that preview collections returned by bpy.utils.previews
    # are regular py objects - you can use them to store custom data.
    import bpy.utils.previews
    pcoll = bpy.utils.previews.new()

    # path to the folder where the icon is
    # the path is calculated relative to this py file inside the addon folder
    my_icons_dir = os.path.join(os.path.dirname(__file__), "icons")

    # load a preview thumbnail of a file and store in the previews collection
    pcoll.load("my_icon", os.path.join(my_icons_dir, "icon-image.png"), 'IMAGE')

    preview_collections["main"] = pcoll

    bpy.utils.register_class(PreviewsExamplePanel)


def unregister():

    for pcoll in preview_collections.values():
        bpy.utils.previews.remove(pcoll)
    preview_collections.clear()

    bpy.utils.unregister_class(PreviewsExamplePanel)


if __name__ == "__main__":
    register()