official/regenerate_thumbnails - add a script to fix skull thumbnails

                                 by dropping the cache for the image
                                 and regenerating it.  Adds a button
                                 to the actions on selected images
                                 module.  Also has a shortcut to
                                 apply the script by hovering and
                                 triggering the shortcut.

Author: wpferguson

official/regenerate_thumbnails.lua

@@ -0,0 +1,264 @@
+--[[
+
+    regenerate_thumbnails.lua - regenerate mipmap cache for selected images
+
+    Copyright (C) 2025 Bill Ferguson <wpferguson@gmail.com>.
+
+    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 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    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.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+]]
+--[[
+    regenerate_thumbnails - regenerate mipmap cache for selected images
+
+    regenerate_thumbnails drops the cached thumbnail for each selected image
+    and generates a new thumbnail.
+
+    ADDITIONAL SOFTWARE NEEDED FOR THIS SCRIPT
+    None
+
+    USAGE
+    * enable the script in script_manager
+    * assign a shortcut, if desired, to apply the script by hovering
+      over a skull and using the shortcut to regenerate the thumbnail
+
+    BUGS, COMMENTS, SUGGESTIONS
+    Bill Ferguson <wpferguson@gmail.com>
+
+    CHANGES
+]]
+
+local dt = require "darktable"
+local du = require "lib/dtutils"
+-- local df = require "lib/dtutils.file"
+-- local ds = require "lib/dtutils.string"
+-- local dtsys = require "lib/dtutils.system"
+local log = require "lib/dtutils.log"
+-- local debug = require "darktable.debug"
+
+
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+-- A P I  C H E C K
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+
+du.check_min_api_version("7.0.0", MODULE)   -- choose the minimum version that contains the features you need
+
+
+-- - - - - - - - - - - - - - - - - - - - - - - - - -
+-- I 1 8 N
+-- - - - - - - - - - - - - - - - - - - - - - - - - -
+
+local gettext = dt.gettext.gettext
+
+local function _(msgid)
+    return gettext(msgid)
+end
+
+
+-- - - - - - - - - - - - - - - - - - - - - - - - - -
+-- S C R I P T  M A N A G E R  I N T E G R A T I O N
+-- - - - - - - - - - - - - - - - - - - - - - - - - -
+
+local script_data = {}
+
+script_data.destroy = nil           -- function to destory the script
+script_data.destroy_method = nil    -- set to hide for libs since we can't destroy them commpletely yet
+script_data.restart = nil           -- how to restart the (lib) script after it's been hidden - i.e. make it visible again
+script_data.show = nil              -- only required for libs since the destroy_method only hides them
+
+script_data.metadata = {
+  name = _("regenerate_thumbnails"),         -- visible name of script
+  purpose = _("regenerate mipmap cache for selected images"),   -- purpose of script
+  author = "Bill Ferguson <wpferguson@gmail.com>",   -- your name and optionally e-mail address
+  help = "https://docs.darktable.org/lua/development/lua.scripts.manual/scripts/official/regenerate_thumbnails"  -- URL to help/documentation
+}
+
+
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+-- C O N S T A N T S
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+
+local MODULE <const> = "regenerate_thumbnails"
+local DEFAULT_LOG_LEVEL <const> = log.info
+local TMP_DIR <const> = dt.configuration.tmp_dir
+
+-- path separator
+local PS <const> = dt.configuration.running_os == "windows" and "\\" or "/"
+
+-- command separator
+local CS <const> = dt.configuration.running_os == "windows" and "&" or ";"
+
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+-- L O G  L E V E L
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+
+log.log_level(DEFAULT_LOG_LEVEL)
+
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+-- N A M E  S P A C E
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+
+local regenerate_thumbnails = {}
+
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+-- G L O B A L  V A R I A B L E S
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+-- P R E F E R E N C E S
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+-- A L I A S E S
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+
+local namespace = regenerate_thumbnails
+local rt = regenerate_thumbnails
+
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+-- F U N C T I O N S
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+
+-------------------
+-- helper functions
+-------------------
+
+local function set_log_level(level)
+  local old_log_level = log.log_level()
+  log.log_level(level)
+  return old_log_level
+end
+
+local function restore_log_level(level)
+  log.log_level(level)
+end
+
+local function pref_read(name, pref_type)
+  local old_log_level = set_log_level(sm.log_level)
+
+  log.msg(log.debug, "name is " .. name .. " and type is " .. pref_type)
+
+  local val = dt.preferences.read(MODULE, name, pref_type)
+
+  log.msg(log.debug, "read value " .. tostring(val))
+
+  restore_log_level(old_log_level)
+  return val
+end
+
+local function pref_write(name, pref_type, value)
+  local old_log_level = set_log_level(sm.log_level)
+
+  log.msg(log.debug, "writing value " .. tostring(value) .. " for name " .. name)
+
+  dt.preferences.write(MODULE, name, pref_type, value)
+
+  restore_log_level(old_log_level)
+end
+
+local function stop_job()
+  rt.job.valid = false
+end
+
+local function generate_thumbnails(images)
+  local has_job = false
+
+  if #images > 50 then
+    rt.job = dt.gui.create_job("regenerating thumbnails", true, stop_job)
+    has_job = true
+  end
+
+  for count, image in ipairs(images) do
+    image:drop_cache()
+    image:generate_cache(true, 1, 3)
+    if has_job then
+      if count % 10 == 0 then
+        rt.job.percent = count / #images
+      end
+    end
+  end
+  if has_job then
+    rt.job.valid = false
+  end
+end
+
+local function update_button_sensitivity()
+  if #dt.gui.action_images > 0 then
+    dt.gui.libs.image.set_sensitive(MODULE, true)
+  else
+    dt.gui.libs.image.set_sensitive(MODULE, false)
+  end
+end
+
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+-- M A I N  P R O G R A M
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+-- U S E R  I N T E R F A C E
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+
+dt.gui.libs.image.register_action(
+  MODULE, 
+  _("generate thumbnails"),
+  function(event, images)
+    generate_thumbnails(images) 
+  end,
+  _("generate thumbnails")
+)
+
+update_button_sensitivity()
+
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+-- D A R K T A B L E  I N T E G R A T I O N 
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+
+local function destroy()
+  dt.destroy_event(MODULE, "selection-changed")
+  dt.destroy_event(MODULE, "mouse-over-image-changed")
+  dt.gui.libs.image.destroy_action(MODULE, "regenerate thumbnails")
+end
+
+script_data.destroy = destroy
+
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+-- E V E N T S
+-- - - - - - - - - - - - - - - - - - - - - - - - 
+
+dt.register_event(MODULE, "shortcut",
+  function(event, shortcut)
+    local images = dt.gui.action_images
+    if images then
+      generate_thumbnails(images)
+    end
+  end, "regenerate thumbnails"
+)
+
+dt.register_event(MODULE, "selection-changed",
+  function(event)
+    update_button_sensitivity()
+  end
+)
+
+dt.register_event(MODULE, "mouse-over-image-changed",
+  function(event, image)
+    if #dt.gui.selection() < 1 then
+      if image then
+        dt.gui.libs.image.set_sensitive(MODULE, true)
+      else
+        dt.gui.libs.image.set_sensitive(MODULE, false)
+      end
+    end
+  end
+)
+
+return script_data