From 83d60edeafe02757ec2f13ef0ea285116af162b0 Mon Sep 17 00:00:00 2001
From: michuNEEO <michael@neeo.com>
Date: Sun, 13 Sep 2015 14:31:22 +0200
Subject: [PATCH] poc to support colortype 2

---
 lib/chunkstream.js     |  0
 lib/constants.js       |  0
 lib/crc.js             |  0
 lib/filter-pack.js     | 45 ++++++++++++++++++++----------------------
 lib/packer.js          | 19 ++++++++++++------
 lib/paeth-predictor.js | 32 +++++++++++++++---------------
 lib/png.js             |  2 +-
 7 files changed, 51 insertions(+), 47 deletions(-)
 mode change 100755 => 100644 lib/chunkstream.js
 mode change 100755 => 100644 lib/constants.js
 mode change 100755 => 100644 lib/crc.js
 mode change 100755 => 100644 lib/packer.js
 mode change 100755 => 100644 lib/png.js

diff --git a/lib/chunkstream.js b/lib/chunkstream.js
old mode 100755
new mode 100644
diff --git a/lib/constants.js b/lib/constants.js
old mode 100755
new mode 100644
diff --git a/lib/crc.js b/lib/crc.js
old mode 100755
new mode 100644
diff --git a/lib/filter-pack.js b/lib/filter-pack.js
index 8899ceb..dd2f368 100644
--- a/lib/filter-pack.js
+++ b/lib/filter-pack.js
@@ -3,7 +3,6 @@
 var paethPredictor = require('./paeth-predictor');
 
 function filterNone(pxData, pxPos, byteWidth, rawData, rawPos) {
-
   pxData.copy(rawData, rawPos, pxPos, pxPos + byteWidth);
 }
 
@@ -18,23 +17,23 @@ function filterSumNone(pxData, pxPos, byteWidth) {
   return sum;
 }
 
-function filterSub(pxData, pxPos, byteWidth, rawData, rawPos) {
+function filterSub(pxData, pxPos, byteWidth, rawData, rawPos, BPP) {
 
   for (var x = 0; x < byteWidth; x++) {
 
-    var left = x >= 4 ? pxData[pxPos + x - 4] : 0;
+    var left = x >= BPP ? pxData[pxPos + x - BPP] : 0;
     var val = pxData[pxPos + x] - left;
 
     rawData[rawPos + x] = val;
   }
 }
 
-function filterSumSub(pxData, pxPos, byteWidth) {
+function filterSumSub(pxData, pxPos, byteWidth, BPP) {
 
   var sum = 0;
   for (var x = 0; x < byteWidth; x++) {
 
-    var left = x >= 4 ? pxData[pxPos + x - 4] : 0;
+    var left = x >= BPP ? pxData[pxPos + x - BPP] : 0;
     var val = pxData[pxPos + x] - left;
 
     sum += Math.abs(val);
@@ -43,7 +42,7 @@ function filterSumSub(pxData, pxPos, byteWidth) {
   return sum;
 }
 
-function filterUp(pxData, pxPos, byteWidth, rawData, rawPos) {
+function filterUp(pxData, pxPos, byteWidth, rawData, rawPos, BPP) {
 
   for (var x = 0; x < byteWidth; x++) {
 
@@ -54,7 +53,7 @@ function filterUp(pxData, pxPos, byteWidth, rawData, rawPos) {
   }
 }
 
-function filterSumUp(pxData, pxPos, byteWidth) {
+function filterSumUp(pxData, pxPos, byteWidth, BPP) {
 
   var sum = 0;
   var length = pxPos + byteWidth;
@@ -69,11 +68,11 @@ function filterSumUp(pxData, pxPos, byteWidth) {
   return sum;
 }
 
-function filterAvg(pxData, pxPos, byteWidth, rawData, rawPos) {
+function filterAvg(pxData, pxPos, byteWidth, rawData, rawPos, BPP) {
 
   for (var x = 0; x < byteWidth; x++) {
 
-    var left = x >= 4 ? pxData[pxPos + x - 4] : 0;
+    var left = x >= BPP ? pxData[pxPos + x - BPP] : 0;
     var up = pxPos > 0 ? pxData[pxPos + x - byteWidth] : 0;
     var val = pxData[pxPos + x] - ((left + up) >> 1);
 
@@ -81,12 +80,12 @@ function filterAvg(pxData, pxPos, byteWidth, rawData, rawPos) {
   }
 }
 
-function filterSumAvg(pxData, pxPos, byteWidth) {
+function filterSumAvg(pxData, pxPos, byteWidth, BPP) {
 
   var sum = 0;
   for (var x = 0; x < byteWidth; x++) {
 
-    var left = x >= 4 ? pxData[pxPos + x - 4] : 0;
+    var left = x >= BPP ? pxData[pxPos + x - BPP] : 0;
     var up = pxPos > 0 ? pxData[pxPos + x - byteWidth] : 0;
     var val = pxData[pxPos + x] - ((left + up) >> 1);
 
@@ -96,27 +95,26 @@ function filterSumAvg(pxData, pxPos, byteWidth) {
   return sum;
 }
 
-function filterPaeth(pxData, pxPos, byteWidth, rawData, rawPos) {
+function filterPaeth(pxData, pxPos, byteWidth, rawData, rawPos, BPP) {
 
   for (var x = 0; x < byteWidth; x++) {
 
-    var left = x >= 4 ? pxData[pxPos + x - 4] : 0;
+    var left = x >= BPP ? pxData[pxPos + x - BPP] : 0;
     var up = pxPos > 0 ? pxData[pxPos + x - byteWidth] : 0;
-    var upleft = pxPos > 0 && x >= 4 ? pxData[pxPos + x - (byteWidth + 4)] : 0;
+    var upleft = pxPos > 0 && x >= BPP ? pxData[pxPos + x - (byteWidth + BPP)] : 0;
     var val = pxData[pxPos + x] - paethPredictor(left, up, upleft);
 
     rawData[rawPos + x] = val;
   }
 }
 
-function filterSumPaeth(pxData, pxPos, byteWidth) {
-
+function filterSumPaeth(pxData, pxPos, byteWidth, BPP) {
   var sum = 0;
   for (var x = 0; x < byteWidth; x++) {
 
-    var left = x >= 4 ? pxData[pxPos + x - 4] : 0;
+    var left = x >= BPP ? pxData[pxPos + x - BPP] : 0;
     var up = pxPos > 0 ? pxData[pxPos + x - byteWidth] : 0;
-    var upleft = pxPos > 0 && x >= 4 ? pxData[pxPos + x - (byteWidth + 4)] : 0;
+    var upleft = pxPos > 0 && x >= BPP ? pxData[pxPos + x - (byteWidth + BPP)] : 0;
     var val = pxData[pxPos + x] - paethPredictor(left, up, upleft);
 
     sum += Math.abs(val);
@@ -141,7 +139,7 @@ var filterSums = {
   4: filterSumPaeth
 };
 
-module.exports = function(pxData, width, height, options) {
+module.exports = function(pxData, width, height, options, bpp) {
 
   var filterTypes;
   if (!('filterType' in options) || options.filterType === -1) {
@@ -154,7 +152,7 @@ module.exports = function(pxData, width, height, options) {
     throw new Error('unrecognised filter types');
   }
 
-  var byteWidth = width << 2;
+  var byteWidth = width * bpp;
   var rawPos = 0;
   var pxPos = 0;
   var rawData = new Buffer((byteWidth + 1) * height);
@@ -167,8 +165,7 @@ module.exports = function(pxData, width, height, options) {
       var min = Infinity;
 
       for (var i = 0; i < filterTypes.length; i++) {
-        var sum = filterSums[filterTypes[i]](pxData, pxPos, byteWidth);
-
+        var sum = filterSums[filterTypes[i]](pxData, pxPos, byteWidth, bpp);
         if (sum < min) {
           sel = filterTypes[i];
           min = sum;
@@ -178,9 +175,9 @@ module.exports = function(pxData, width, height, options) {
 
     rawData[rawPos] = sel;
     rawPos++;
-    filters[sel](pxData, pxPos, byteWidth, rawData, rawPos);
+    filters[sel](pxData, pxPos, byteWidth, rawData, rawPos, bpp);
     rawPos += byteWidth;
     pxPos += byteWidth;
   }
   return rawData;
-};
\ No newline at end of file
+};
diff --git a/lib/packer.js b/lib/packer.js
old mode 100755
new mode 100644
index ac2ccc6..abc0091
--- a/lib/packer.js
+++ b/lib/packer.js
@@ -8,6 +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 Packer = module.exports = function(options) {
   Stream.call(this);
@@ -18,6 +20,8 @@ var Packer = module.exports = function(options) {
   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;
 
   this.readable = true;
 };
@@ -25,17 +29,20 @@ util.inherits(Packer, Stream);
 
 
 Packer.prototype.pack = function(data, width, height, gamma) {
-
   // Signature
   this.emit('data', new Buffer(constants.PNG_SIGNATURE));
-  this.emit('data', this._packIHDR(width, height));
+  this.emit('data', this._packIHDR(width, height, this._options.bitDepth, this._options.colorType));
 
   if (gamma) {
     this.emit('data', this._packGAMA(gamma));
   }
 
   // filter pixel data
-  var filteredData = filter(data, width, height, this._options);
+  var bpp = 4;
+  if (this._options.colorType === COLOR_TYPE_TRUECOLOR) {
+    bpp = 3;
+  }
+  var filteredData = filter(data, width, height, this._options, bpp);
 
   // compress it
   var deflate = this._options.deflateFactory({
@@ -79,13 +86,13 @@ Packer.prototype._packGAMA = function(gamma) {
   return this._packChunk(constants.TYPE_gAMA, buf);
 };
 
-Packer.prototype._packIHDR = function(width, height) {
+Packer.prototype._packIHDR = function(width, height, bitDepth, colorType) {
 
   var buf = new Buffer(13);
   buf.writeUInt32BE(width, 0);
   buf.writeUInt32BE(height, 4);
-  buf[8] = 8;
-  buf[9] = 6; // colorType
+  buf[8] = bitDepth;  // Bit depth
+  buf[9] = colorType; // colorType
   buf[10] = 0; // compression
   buf[11] = 0; // filter
   buf[12] = 0; // interlace
diff --git a/lib/paeth-predictor.js b/lib/paeth-predictor.js
index 97c3adf..74d254e 100644
--- a/lib/paeth-predictor.js
+++ b/lib/paeth-predictor.js
@@ -1,17 +1,17 @@
-'use strict';
-
-module.exports = function paethPredictor(left, above, upLeft) {
-
-  var paeth = left + above - upLeft;
-  var pLeft = Math.abs(paeth - left);
-  var pAbove = Math.abs(paeth - above);
-  var pUpLeft = Math.abs(paeth - upLeft);
-
-  if (pLeft <= pAbove && pLeft <= pUpLeft) {
-    return left;
-  }
-  if (pAbove <= pUpLeft) {
-    return above;
-  }
-  return upLeft;
+'use strict';
+
+module.exports = function paethPredictor(left, above, upLeft) {
+
+  var paeth = left + above - upLeft;
+  var pLeft = Math.abs(paeth - left);
+  var pAbove = Math.abs(paeth - above);
+  var pUpLeft = Math.abs(paeth - upLeft);
+
+  if (pLeft <= pAbove && pLeft <= pUpLeft) {
+    return left;
+  }
+  if (pAbove <= pUpLeft) {
+    return above;
+  }
+  return upLeft;
 };
\ No newline at end of file
diff --git a/lib/png.js b/lib/png.js
old mode 100755
new mode 100644
index 1c8627f..c60778e
--- a/lib/png.js
+++ b/lib/png.js
@@ -160,4 +160,4 @@ PNG.adjustGamma = function(src) {
 
 PNG.prototype.adjustGamma = function() {
   PNG.adjustGamma(this);
-};
\ No newline at end of file
+};