Fixed using gm as node_module to identify pages

lib/pdf2img.js

@@ -66,32 +66,35 @@ Pdf2Img.prototype.convert = function(input, callbackreturn) {
 
   async.waterfall([
     // Get pages count
-    function(callback) {
-      var cmd = 'gm identify -format "%p " "' + input + '"';
-      var execSync = require('child_process').execSync;
-      var pageCount = execSync(cmd).toString().match(/[0-9]+/g);
+        function (callback) {
+             gm(input).identify("%p ", function (err, value) {
+                var pageCount = String(value).split(' ');
+
+                if (!pageCount.length) {
+                    callback({
+                        result: 'error',
+                        message: 'Invalid page number.'
+                    }, null);
+                } else {
+                    // Convert selected page
+                    if (options.page !== null) {
+                        if (options.page < pageCount.length) {
+                            callback(null, [options.page]);
+                        } else {
+                            callback({
+                                result: 'error',
+                                message: 'Invalid page number.'
+                            }, null);
+                        }
+                    } else  {
+                        callback(null, pageCount);
+                    }
+                }
+
+            })
+
+        },
 
-      if (!pageCount.length) {
-        return callback({
-          result: 'error',
-          message: 'Invalid page number.'
-        }, null);
-      }
-
-      // Convert selected page
-      if (options.page !== null) {
-        if (options.page < pageCount.length) {
-          return callback(null, [options.page]);
-        } else {
-          return callback({
-            result: 'error',
-            message: 'Invalid page number.'
-          }, null);
-        }
-      }
-
-      return callback(null, pageCount);
-    },
 
     // Convert pdf file
     function(pages, callback) {