diff --git a/README.md b/README.md
index 3bb8c8c..e22c03c 100644
--- a/README.md
+++ b/README.md
@@ -9,13 +9,14 @@ Based on [pngjs](https://github.com/niegowski/node-pngjs) with the follow enhanc
   * Support for reading 1,2,4 & 16 bit files
   * Support for reading interlace files
   * Support for reading `tTRNS` transparent colours
+  * Support for writing colortype 2 (RGB) and colortype 6 (RGBA)
   * Sync interface as well as async
   * API compatible with pngjs and node-pngjs
 
 Known lack of support for:
 
   * Extended PNG e.g. Animation
-  * Writing in different formats
+  * Writing in different formats, colortype 0 (greyscale), colortype 3 (indexed color), colortype 4 (greyscale with alpha)
   * Synchronous write
 
 Requirements
diff --git a/lib/chunkstream.js b/lib/chunkstream.js
index 59292c5..56719bd 100644
--- a/lib/chunkstream.js
+++ b/lib/chunkstream.js
@@ -199,11 +199,11 @@ ChunkStream.prototype._process = function() {
       }
     }
 
-    if (this._buffers && this._buffers.length > 0 && this._buffers[0] == null) {
+    if (this._buffers && this._buffers.length > 0 && this._buffers[0] === null) {
       this._end();
     }
   }
-  catch(ex) {
+  catch (ex) {
     this.emit('error', ex);
   }
 };
diff --git a/lib/filter-pack.js b/lib/filter-pack.js
index dd2f368..94dab44 100644
--- a/lib/filter-pack.js
+++ b/lib/filter-pack.js
@@ -42,7 +42,7 @@ function filterSumSub(pxData, pxPos, byteWidth, BPP) {
   return sum;
 }
 
-function filterUp(pxData, pxPos, byteWidth, rawData, rawPos, BPP) {
+function filterUp(pxData, pxPos, byteWidth, rawData, rawPos) {
 
   for (var x = 0; x < byteWidth; x++) {
 
@@ -53,7 +53,7 @@ function filterUp(pxData, pxPos, byteWidth, rawData, rawPos, BPP) {
   }
 }
 
-function filterSumUp(pxData, pxPos, byteWidth, BPP) {
+function filterSumUp(pxData, pxPos, byteWidth) {
 
   var sum = 0;
   var length = pxPos + byteWidth;
diff --git a/lib/packer.js b/lib/packer.js
index abc0091..e342cc8 100644
--- a/lib/packer.js
+++ b/lib/packer.js
@@ -8,8 +8,8 @@ var filter = require('./filter-pack');
 var CrcStream = require('./crc');
 var constants = require('./constants');
 
-var COLOR_TYPE_TRUECOLOR = 2;
-var COLOR_TYPE_TRUECOLOR_WITH_ALPHA = 6;
+var COLORTYPE_TRUECOLOR = 2;
+var COLORTYPE_TRUECOLOR_ALPHA = 6;
 
 var Packer = module.exports = function(options) {
   Stream.call(this);
@@ -17,11 +17,11 @@ var Packer = module.exports = function(options) {
   this._options = options;
 
   options.deflateChunkSize = options.deflateChunkSize || 32 * 1024;
-  options.deflateLevel = options.deflateLevel != null ? options.deflateLevel : 9;
-  options.deflateStrategy = options.deflateStrategy != null ? options.deflateStrategy : 3;
+  options.deflateLevel = options.deflateLevel !== null ? options.deflateLevel : 9;
+  options.deflateStrategy = options.deflateStrategy !== null ? options.deflateStrategy : 3;
   options.deflateFactory = options.deflateFactory || zlib.createDeflate;
   options.bitDepth = options.bitDepth || 8;
-  options.colorType = (typeof options.colorType=="number") ? options.colorType : COLOR_TYPE_TRUECOLOR_WITH_ALPHA;
+  options.colorType = (typeof options.colorType === 'number') ? options.colorType : COLORTYPE_TRUECOLOR_ALPHA;
 
   this.readable = true;
 };
@@ -39,7 +39,7 @@ Packer.prototype.pack = function(data, width, height, gamma) {
 
   // filter pixel data
   var bpp = 4;
-  if (this._options.colorType === COLOR_TYPE_TRUECOLOR) {
+  if (this._options.colorType === COLORTYPE_TRUECOLOR) {
     bpp = 3;
   }
   var filteredData = filter(data, width, height, this._options, bpp);
diff --git a/lib/png.js b/lib/png.js
index c60778e..b4663c8 100644
--- a/lib/png.js
+++ b/lib/png.js
@@ -15,8 +15,8 @@ var PNG = exports.PNG = function(options) {
   this.width = options.width || 0;
   this.height = options.height || 0;
 
-  this.data = this.width > 0 && this.height > 0
-    ? new Buffer(4 * this.width * this.height) : null;
+  this.data = this.width > 0 && this.height > 0 ?
+    new Buffer(4 * this.width * this.height) : null;
 
   if (options.fill && this.data) {
     this.data.fill(0);
diff --git a/package.json b/package.json
index d64ffa1..7976497 100644
--- a/package.json
+++ b/package.json
@@ -9,7 +9,8 @@
     "Luke Page",
     "Pietajan De Potter",
     "Steven Sojka",
-    "liangzeng"
+    "liangzeng",
+    "Michael Vogt"
   ],
   "homepage": "https://github.com/lukeapage/pngjs2",
   "keywords": [
diff --git a/test/bg.png b/test/bg.png
index e4361e0..b1885d9 100644
Binary files a/test/bg.png and b/test/bg.png differ