Add script to create thumbnails/previews of selected images

contrib/create_thumbnails.lua

@@ -0,0 +1,140 @@
+--[[
+Create thumbnails plugin for darktable
+
+  darktable 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.
+
+  darktable 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 darktable.  If not, see <http://www.gnu.org/licenses/>.
+]]
+
+--[[About this Plugin
+This plugin adds the buttons 'create thumbnails' and 'delete thumbnails' to 'selected image[s]' module of darktable's lighttable view.
+
+
+----USAGE----
+Click the 'create thumbnails' button in the 'selected image[s]' module to let the script create full sized previews of all selected images.
+Click the 'delete thumbnails' button in the 'selected image[s]' module to let the script delete all previews/thumbnails of all selected images.
+
+To create (or delete) previews of all images of a collection:
+Use CTRL+A to select all images of current collection and then press the corresponding button.
+]]
+
+local dt = require "darktable"
+local du = require "lib/dtutils"
+
+du.check_min_api_version("8.0.0", "create_thumbnails_button")
+
+-- stop running thumbnail creation
+local function stop_job(job)
+    job.valid = false
+end
+
+-- return "1 image" if amount_of_images is 1 else "<amount_of_images> images"
+local function image_count_to_text(amount_of_images)
+    return amount_of_images .. " image" .. (amount_of_images == 1 and "" or "s")
+end
+
+-- print the given message to the user and log the given message
+local function print_and_log(message)
+    dt.print(message)
+    dt.print_log(message)
+end
+
+-- add button to 'selected images' module
+dt.gui.libs.image.register_action(
+    "create_thumbnails_button",
+    "create thumbnails",
+    function(event, images)
+        print_and_log("creating thumbnails for " .. image_count_to_text(#images) .. " ...")
+
+        -- create a new progress_bar displayed in darktable.gui.libs.backgroundjobs
+        job = dt.gui.create_job("creating thumbnails...", true, stop_job)
+
+        for i, image in pairs(images) do
+            -- generate all thumbnails, a max value of 8 means that also a full size preview image is created
+            -- check only once if the mipmap cache directories exist 
+            image:generate_cache(i == 1, 0, 8)
+
+            -- update progress_bar
+            job.percent = i / #images
+
+            -- sleep for a short moment to give stop_job callback function a chance to run
+            dt.control.sleep(10)
+
+            -- stop early if darktable is shutdown or the cancle button of the progress bar is pressed
+            if dt.control.ending or not job.valid then
+                print_and_log("creating thumbnails canceled after processing " .. i .. "/" .. image_count_to_text(#images) .. "!")
+                break
+            end
+        end
+
+        -- if job was not canceled
+        if(job.valid) then
+            -- stop job and remove progress_bar from ui
+            job.valid = false
+
+            print_and_log("creating thumbnails for " ..  image_count_to_text(#images) .. " done!")
+        end
+    end,
+    "create full sized previews of all selected images"
+)
+
+
+-- add button to 'selected images' module
+dt.gui.libs.image.register_action(
+    "delete_thumbnails_button",
+    "delete thumbnails",
+    function(event, images)
+        print_and_log("deleting thumbnails of " .. image_count_to_text(#images) .. " ...")
+
+        -- create a new progress_bar displayed in darktable.gui.libs.backgroundjobs
+        job = dt.gui.create_job("deleting thumbnails...", true, stop_job)
+
+        for i, image in pairs(images) do
+            -- delete all thumbnails
+            image:drop_cache()
+
+            -- update progress_bar
+            job.percent = i / #images
+
+            -- sleep for a short moment to give stop_job callback function a chance to run
+            dt.control.sleep(10)
+
+            -- stop early if darktable is shutdown or the cancle button of the progress bar is pressed
+            if dt.control.ending or not job.valid then
+                print_and_log("deleting thumbnails canceled after processing " .. i .. "/" .. image_count_to_text(#images) .. "!")
+                break
+            end
+        end
+
+        -- if job was not canceled
+        if(job.valid) then
+            -- stop job and remove progress_bar from ui
+            job.valid = false
+
+            print_and_log("deleting thumbnails of " ..  image_count_to_text(#images) .. " done!")
+        end
+    end,
+    "delete all thumbnails of all selected images"
+)
+
+-- clean up function that is called when this module is getting disabled
+local function destroy()
+    dt.gui.libs.image.destroy_action("create_thumbnails_button")
+    dt.gui.libs.image.destroy_action("delete_thumbnails_button")
+end
+
+
+local script_data = {}
+script_data.destroy = destroy -- 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
+return script_data