generate_image_txt.lua

--[[
    This file is part of darktable,
    copyright (c) 2014 Tobias Ellinghaus

    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/>.
]]
--[[
GENERATE IMAGE TEXT
A script to run a command on images to generate text metadata

The medata will be displayed as an overlay on the image in lighttable mode

USAGE
* require this script from your main lua file
* set a command to run on all image, this command should output text on stdout
* enable image file generation


]]

-- TODO:
--  * enable showing of the txt file (plugins/lighttable/draw_custom_metadata) if this script is enabled
--  * maybe allow a lua command returning text instead of a command line call? both?
--  * make filenames with double quotes (") work

local dt = require "darktable"
local du = require "lib/dtutils"
require "darktable.debug"

local gettext = dt.gettext.gettext

local function _(msg)
  return gettext(msg)
end

du.check_min_api_version("7.0.0", "generate_image_txt") 

-- return data structure for script_manager

local script_data = {}

script_data.metadata = {
  name = "generate_image_txt",
  purpose = _("overlay metadata on the selected image(s)"),
  author = "Tobias Ellinghaus",
  help = "https://docs.darktable.org/lua/stable/lua.scripts.manual/scripts/official/generate_image_txt"
}

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

dt.preferences.register("generate_image_txt",
                        "enabled",
                        "bool",
                        _("create txt sidecars to display with images"),
                        _("the txt files created get shown when the lighttable is zoomed in to one image. also enable the txt overlay setting in the gui tab"),
                        false)

dt.preferences.register("generate_image_txt",
                        "command",
                        "string",
                        _("command to generate the txt sidecar"),
                        _("the output of this command gets written to the txt file. use $(FILE_NAME) for the image file"),
                        "exiv2 $(FILE_NAME)")


local check_command = function(command)
  if not command:find("$(FILE_NAME)", 1, true) then
    dt.print(_("the command for txt sidecars looks bad. better check the preferences"))
  end
end

local function destroy()
  dt.destroy_event("gen_img_txt", "mouse-over-image-changed")
end


local command_setting = dt.preferences.read("generate_image_txt", "command", "string")
check_command(command_setting)

dt.register_event("gen_img_txt", "mouse-over-image-changed", 
    function(event, img)
    -- no need to waste processing time if the image has a txt file already
    if not img or img.has_txt or not dt.preferences.read("generate_image_txt", "enabled", "bool") then
      return
    end

    -- there should be at least one "$(FILE_NAME)" in the command. warn if not, but only once
    local _command_setting = dt.preferences.read("generate_image_txt", "command", "string")
    if not (command_setting == _command_setting) then
      command_setting = _command_setting
      check_command(command_setting)
    end

    -- set the flag to true first so that subsequent runs don't mess with the txt
    img.has_txt = true

    -- next: create the txt

    local img_filename = img.path.."/"..img.filename
    local txt_filename = img.path.."/"..img.filename:match("^[^.]*")..".txt"

    -- better safe than sorry: check if the file maybe exists. this is for example true when shooting raw+jpg
    local file = io.open(txt_filename, "r")
    if file then
      file.close()
      return
    end

    -- we are confident now that it's safe to write the file

    -- compose the command to run
    local command = command_setting:gsub("%$%(FILE_NAME%)", '"'..img_filename..'"')..' > "'..txt_filename..'"'

    -- finally, run it
     dt.control.execute( command)
  end
)

script_data.destroy = destroy

return script_data

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