op_texture_reload_all.py

import bpy
import os
import bmesh
from mathutils import Vector
from collections import defaultdict
from math import pi

class op(bpy.types.Operator):
    bl_idname = "uv.textools_texture_reload_all"
    bl_label = "Reload Textures and remove unused Textures"
    bl_description = "Reload all textures"

    @classmethod
    def poll(cls, context):
        return True

    def execute(self, context):
        main(context)
        return {'FINISHED'}


def main(context):
    count_clear_mat = 0
    count_clear_img = 0
    count_reload = 0

    for material in bpy.data.materials:
        if not material.users:
            count_clear_mat+=1
            material.user_clear()
            bpy.data.materials.remove(material)

    # Clean up unused images
    for image in bpy.data.images:
        if not image.users:
            count_clear_img+=1
            image.user_clear()
            bpy.data.images.remove(image)

    #Reload all File images
    for img in bpy.data.images :
        if img.source == 'FILE' :
            count_reload+=1
            img.reload()

    # Refresh vieport texture
    for window in bpy.context.window_manager.windows:
        screen = window.screen
        for area in screen.areas:
            area.tag_redraw()

    # Show popup on cleared & reloaded items
    message = ""
    if count_reload > 0:
        message+="{}x reloaded. ".format(count_reload)
    if count_clear_mat > 0:
        message+="{}x mat cleared. ".format(count_clear_mat)
    if count_clear_img > 0:
        message+="{}x img cleared.".format(count_clear_img)

    if len(message) > 0:
        bpy.ops.ui.textools_popup('INVOKE_DEFAULT', message=message)
    
bpy.utils.register_class(op)