fujifilm_dynamic_range : first draft

Read RawExposureBias and adjust "EXIF Exposure Bias" based upon this.

Author: dtorop

contrib/fujifilm_dynamic_range.lua

@@ -0,0 +1,73 @@
+--[[ fujifilm_dynamic_range-0.1
+
+Compensate for Fujifilm raw files made using "dynamic range".
+
+Copyright (C) 2020 Dan Torop <[email protected]>
+
+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 2 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, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+]]
+
+--[[About this Plugin
+Support for adjusting darktable exposure by Fujifilm raw exposure
+bias. This corrects for a DR100/DR200/DR400 "dynamic range" setting.
+
+Dependencies:
+- exiftool (https://www.sno.phy.queensu.ca/~phil/exiftool/)
+
+Based upon fujifilm_ratings by Ben Mendis
+
+--]]
+
+local dt = require "darktable"
+local du = require "lib/dtutils"
+local df = require "lib/dtutils.file"
+local gettext = dt.gettext
+
+du.check_min_api_version("4.0.0", "fujifilm_dynamic_range")
+
+gettext.bindtextdomain("fujifilm_dynamic_range", dt.configuration.config_dir.."/lua/locale/")
+
+local function _(msgid)
+	return gettext.dgettext("fujifilm_dynamic_range", msgid)
+end
+
+local function detect_dynamic_range(event, image)
+	-- exiftool knows about the RawExposureBias tag, unlike exiv2, but it is also 10x slower
+	if not df.check_if_bin_exists("exiftool") then
+		dt.print_error(_("exiftool not found"))
+		return
+	end
+	local RAF_filename = df.sanitize_filename(tostring(image))
+	local command = "exiftool -RawExposureBias " .. RAF_filename
+	dt.print_error(command)
+	output = io.popen(command)
+	local raf_result = output:read("*all")
+	output:close()
+	if string.len(raf_result) > 0 then
+		raf_result = string.gsub(raf_result, "^Raw Exposure Bias.-([%d%.%-]+)", "%1")
+		if image.exif_exposure_bias ~= image.exif_exposure_bias then
+			-- is NAN (this is unlikely as RAFs should have ExposureBiasValue set)
+			image.exif_exposure_bias = 0
+		end
+		-- this should be auto-applied if plugins/darkroom/workflow is scene-referred
+		-- FIXME: scene-referred workflow pushes exposure up 0.5 EV, but DR100 pushes up 0.7 EV -- should reduce this by 0.5 EV?
+		image.exif_exposure_bias = image.exif_exposure_bias + tonumber(raf_result)
+		dt.print_error(_("Using RAF exposure bias: ") .. tostring(raf_result))
+	end
+end
+
+dt.register_event("post-import-image", detect_dynamic_range)
+
+print(_("fujifilm_dynamic_range loaded."))