Steam Achievement Image Converter

achievementconvert.lua

-- Author: Zachary Burke
-- License: MIT
--
-- Steam Achievement Image Converter
--
--                           /-----------\ ----> Color JPG
--         (Color PNG) ----> |This script|
--                           \-----------/ ----> Grayscale JPG
--
-- Each Steam Achievement requires two 64x64 JPG files. One image for the unachieved state and the
-- other for the achieved state. It is recommended that the achieved state be in color while the
-- unachieved state be grayscale.
--
-- This script goes through all PNG files in a folder and generates the two required JPG files
-- for each image.

-- REQUIREMENTS:
--  * ImageMagick installed and in your path. The "convert" command is used. Note that windows
--    also has a convert command in the path that is not at all the same thing!
--

lfs = require "lfs"

--
-- Return true if the given file is a png
--
function fileIsPNG ( sFilename )
	if sFilename then
		return string.match ( string.lower ( sFilename ), ".png" ) ~= nil
	end

	return false
end

--
-- Returns filename, ext for a given file
--
function getFileNameAndExtension ( sFilename )
	if sFilename then
		-- match (anything not a .).(anything not a .)
		for k, v in string.gmatch ( sFilename, "([^\.]+)\.([^\.]+)" ) do
			return k, v
		end
	end

	return nil, nil
end

--
-- Loop through all files in the current folder
--
for file in lfs.dir('.') do
	--
	-- For each PNG found:
	--   1. Convert it to a .jpg with the same filename
	--   2. Convert it to a desaturated .jpg with the appended text "_off"
	--		ex. level1.png -> level1_off.jpg
	--
	if fileIsPNG ( file ) then
		local sName, sExt = getFileNameAndExtension ( file )
		if sName and sExt then
			-- 1.
			os.execute ( 'convert "' .. file .. '" "' .. sName .. '.jpg"' )

			-- 2.
			os.execute ( 'convert "' .. file .. '" -colorspace Gray "' .. sName .. '_off.jpg"' )
		end
	end
end