Fix PNG memory leak

.babelrc

@@ -0,0 +1,15 @@
+{
+  "presets": [
+    [
+      "env", 
+      {
+        "targets": {
+          "node": "6.10"
+        }
+      }
+    ]
+  ],
+  "plugins": [
+    "babel-plugin-add-module-exports"
+  ]  
+}

.eslintrc

@@ -0,0 +1,3 @@
+{
+  "extends": "eslint:recommended"
+}

.gitignore

@@ -1,12 +1,13 @@
 lib/font/tables/.DS_Store
 .DS_Store
 /node_modules/
-/tests/
 node-zlib/
 src/
 playground/
 build/
 js/
 demo/bundle.js
 *.html
-!demo/browser.html
+!demo/browser.html
+.idea/
+package-lock.json

docs/images.coffee.md

@@ -23,25 +23,25 @@ Here is an example showing some of these options.
 
     # Scale proprotionally to the specified width
     doc.image('images/test.jpeg', 0, 15, width: 300)
-       .text('Proportional to width', 0, 0)
+    doc.text('Proportional to width', 0, 0)
 
     # Fit the image within the dimensions
     doc.image('images/test.jpeg', 320, 15, fit: [100, 100])
-       .rect(320, 15, 100, 100)
+    doc.rect(320, 15, 100, 100)
        .stroke()
        .text('Fit', 320, 0)
 
     # Stretch the image
     doc.image('images/test.jpeg', 320, 145, width: 200, height: 100)
-       .text('Stretch', 320, 130)
+    doc.text('Stretch', 320, 130)
 
     # Scale the image
     doc.image('images/test.jpeg', 320, 280, scale: 0.25)
-       .text('Scale', 320, 265)
+    doc.text('Scale', 320, 265)
 
     # Fit the image in the dimensions, and center it both horizontally and vertically
     doc.image('images/test.jpeg', 430, 15, fit: [100, 100], align: 'center', valign: 'center')
-       .rect(430, 15, 100, 100)
+    doc.rect(430, 15, 100, 100)
        .stroke()
        .text('Centered', 430, 0)
 
@@ -51,5 +51,7 @@ This example produces the following output:
 
 ![0](images/images.png "150")
 
-That is all there is to adding images to your PDF documents with PDFKit. Now
-let's look at adding annotations.
+**NOTE:** As of version 0.9.0, doc.image() returns a promise, since pngs need to decompressed.  While this takes a small amount of resources for a single image, in large numbers the decompression can use a large amount of both CPU and memory and it makes sense to wait for a batch to complete before adding another image.
+
+That is all there is to adding images to your PDF documents with PDFKit. Next let's look at adding annotations.
+

lib/abstract_reference.js

@@ -0,0 +1,13 @@
+// TODO: This file was created by bulk-decaffeinate.
+// Sanity-check the conversion and remove this comment.
+/*
+PDFAbstractReference - abstract class for PDF reference
+*/
+
+class PDFAbstractReference {
+  toString() {
+    throw new Error('Must be implemented by subclasses');
+  }
+}
+
+export default PDFAbstractReference;