return & use lwip-stripped image in skins.save_image

no need to pass along (possibly) bulky or broken images!
see #147

lib/helpers.js

@@ -42,7 +42,7 @@ function store_skin(rid, userId, profile, cache_details, callback) {
               if (err1 || !img) {
                 callback(err1, null);
               } else {
-                skins.save_image(img, skinpath, function(skin_err) {
+                skins.save_image(img, skinpath, function(skin_err, skin_img) {
                   if (skin_err) {
                     callback(skin_err, null);
                   } else {
@@ -95,7 +95,7 @@ function store_cape(rid, userId, profile, cache_details, callback) {
               if (net_err || !img) {
                 callback(net_err, null);
               } else {
-                skins.save_image(img, capepath, function(skin_err) {
+                skins.save_image(img, capepath, function(skin_err, skin_img) {
                   logging.debug(rid, "cape saved");
                   callback(skin_err, cape_hash);
                 });

lib/networking.js

@@ -197,8 +197,8 @@ exp.save_texture = function(rid, tex_hash, outpath, callback) {
       if (err) {
         callback(err, response, null);
       } else {
-        skins.save_image(img, outpath, function(img_err) {
-          callback(img_err, response, img);
+        skins.save_image(img, outpath, function(img_err, saved_img) {
+          callback(img_err, response, saved_img);
         });
       }
     });

lib/skins.js

@@ -134,18 +134,18 @@ exp.open_skin = function(rid, skinpath, callback) {
 };
 
 // write the image +buffer+ to the +outpath+ file
-// callback: error
+// the image is stripped down by lwip.
+// callback: error, image
 exp.save_image = function(buffer, outpath, callback) {
   lwip.open(buffer, "png", function(err, image) {
     if (err) {
-      callback(err);
+      callback(err, image);
     } else {
-      image.batch()
-      .writeFile(outpath, function(write_err) {
+      image.writeFile(outpath, function(write_err) {
         if (write_err) {
-          callback(write_err);
+          callback(write_err, image);
         } else {
-          callback(null);
+          callback(null, image);
         }
       });
     }