use nginx variable to get magick (#20)

* use nginx variable to get magick

* remove comments

test/test_magick.lua

@@ -1,12 +1,21 @@
-local magick = "/usr/local/ImageMagick/bin/magick"
-local tmp = io.open(magick,"r")
-if tmp == nil then
-    -- in mac os
-    magick = "/usr/local/bin/magick"
-else
-    io.close(tmp)
+-- read from nginx var config
+local magick = ngx.var.magick
+ngx.log(ngx.ERR, 'var', magick)
+-- or use which command to get
+if not magick then
+    local exec = io.popen("which magick")
+    local tmp = exec:read("*a")
+    magick = string.gsub(tmp, "%s+", "")
+    exec:close()
 end
-print(magick)
+if not magick then
+    ngx.status = 500
+    ngx.say("image magick not found.")
+    return
+end
+
+ngx.say(magick)
+
 
 --local origin = {
 --    "/Users/moicen/Music/alchemy/Song-of-joy.png",