Looks like gd.createFromPtr() fires callback multiple times in some conditions:
/usr/home/rei/node_modules/async/lib/async.js:22
if (called) throw new Error("Callback was already called.");
^
Error: Callback was already called.
at /usr/home/rei/node_modules/async/lib/async.js:22:31
at /usr/home/rei/node_modules/async/lib/async.js:226:17
at /usr/home/rei/index.js:98:13
at /usr/home/rei/node_modules/easy-gd/index.js:53:25
at /usr/home/rei/node_modules/easy-gd/node_modules/exif/lib/exif/ExifImage.js:46:5
at ExifImage.processImage (/usr/home/rei/node_modules/easy-gd/node_modules/exif/lib/exif/ExifImage.js:116:2)
at ExifImage.loadImage (/usr/home/rei/node_modules/easy-gd/node_modules/exif/lib/exif/ExifImage.js:62:8)
at new ExifImage (/usr/home/rei/node_modules/easy-gd/node_modules/exif/lib/exif/ExifImage.js:44:8)
at Object.gd.createFromPtr (/usr/home/rei/node_modules/easy-gd/index.js:52:27)
at /usr/home/rei/index.js:90:12
Looks like gd.createFromPtr() fires callback multiple times in some conditions: