From b9293eaa2b5e6fcd93e8ef3e10fedbac753c506a Mon Sep 17 00:00:00 2001
From: Luke Page <luke.a.page@gmail.com>
Date: Sun, 2 Aug 2015 23:09:08 +0100
Subject: [PATCH] support for transparent colour blocks without palettes

---
 lib/bitmapper.js | 22 +++++++---------
 lib/parser.js    | 66 ++++++++++++++++++++++++++++++++++++++----------
 test/test.js     |  2 +-
 3 files changed, 62 insertions(+), 28 deletions(-)

diff --git a/lib/bitmapper.js b/lib/bitmapper.js
index 1be31d8..6fa1823 100644
--- a/lib/bitmapper.js
+++ b/lib/bitmapper.js
@@ -17,8 +17,7 @@ function bitRetriever(data, depth) {
       case 16:
         var byte2 = data[i];
         i++;
-        byte = Math.floor((((byte << 8) + byte2) * 255) / (Math.pow(2, 16) - 1) + 0.5);
-        leftOver.push(byte);
+        leftOver.push(((byte << 8) + byte2));
         break;
       case 4:
         var byte2 = byte & 0x0f;
@@ -70,8 +69,14 @@ exports.dataToBitMap = function(data, width, height, bpp, depth, interlace) {
   if (depth !== 8) {
     var bits = bitRetriever(data, depth);
   }
-  var pxData = new Buffer(width * height * 4);
-  var maxBit = depth >= 8 ? 255 : (Math.pow(2, depth) - 1);
+  var pxData;
+  if (depth <= 8) {
+    pxData = new Buffer(width * height * 4);
+  } else {
+    // TODO: could be more effecient and use a buffer but change how we write to use 16 bit write methods with index * 2
+    pxData = new Array(width * height * 4);
+  }
+  var maxBit = Math.pow(2, depth) - 1;
   var rawPos = 0;
   var pixelData;
   var images;
@@ -90,15 +95,6 @@ exports.dataToBitMap = function(data, width, height, bpp, depth, interlace) {
     images = [{width: width, height: height}];
   }
 
-  for (var y = 0; y < height; y++) {
-    for (var x = 0; x < width; x++) {
-      pxData[(y * 4 * width) + (x * 4) + 0] = 255;
-      pxData[(y * 4 * width) + (x * 4) + 1] = 0;
-      pxData[(y * 4 * width) + (x * 4) + 2] = 0;
-      pxData[(y * 4 * width) + (x * 4) + 3] = 255;
-    }
-  }
-
   for(var imageIndex = 0; imageIndex < images.length; imageIndex++) {
     var imageWidth = images[imageIndex].width;
     var imageHeight = images[imageIndex].height;
diff --git a/lib/parser.js b/lib/parser.js
index cce23c2..72bb3c5 100644
--- a/lib/parser.js
+++ b/lib/parser.js
@@ -252,6 +252,13 @@ Parser.prototype._parseTRNS = function(data) {
 
   // for colorType 0 (grayscale) and 2 (rgb)
   // there might be one gray/color defined as transparent
+  if (this._colorType === 0) {
+    // grey, 2 bytes
+    this._transColor = [data.readUInt16BE(0)];
+  }
+  if (this._colorType === 2) {
+    this._transColor = [data.readUInt16BE(0), data.readUInt16BE(2), data.readUInt16BE(4)];
+  }
 
   this._handleChunkEnd();
 };
@@ -300,7 +307,9 @@ Parser.prototype._parseIEND = function(data) {
   this.finished();
 };
 
-Parser.prototype.reverseFiltered = function(data, depth, width, height) {
+Parser.prototype.reverseFiltered = function(indata, depth, width, height) {
+
+  var outdata = indata; // only different for 16 bits
 
   if (this._colorType == 3) { // paletted
     //console.log("paletted");
@@ -312,28 +321,57 @@ Parser.prototype.reverseFiltered = function(data, depth, width, height) {
 
       for (var x = 0; x < width; x++) {
         var pxPos = pxRowPos + (x << 2),
-          color = this._palette[data[pxPos]];
+          color = this._palette[indata[pxPos]];
 
         for (var i = 0; i < 4; i++)
-          data[pxPos + i] = color[i];
+          indata[pxPos + i] = color[i];
       }
     }
-  } else if (depth < 8) {
-    //console.log("adjusting");
+  } else {
     var pxLineLength = width << 2;
-    var maxOutSample = 255;
-    var maxInSample = Math.pow(2, depth) - 1;
 
-    for (var y = 0; y < height; y++) {
-      var pxRowPos = y * pxLineLength;
+    if (this._transColor) {
+      for (var y = 0; y < height; y++) {
+        var pxRowPos = y * pxLineLength;
 
-      for (var x = 0; x < width; x++) {
-        var pxPos = pxRowPos + (x << 2);
-        for (var i = 0; i < 4; i++)
-          data[pxPos + i] = Math.floor((data[pxPos + i] * maxOutSample) / maxInSample + 0.5);
+        for (var x = 0; x < width; x++) {
+          var pxPos = pxRowPos + (x << 2);
+          var makeTrans = false;
+          //console.log(pxPos);
+          if (this._transColor.length === 1) {
+            if (this._transColor[0] === indata[pxPos]) {
+              makeTrans = true;
+            }
+          } else if (this._transColor[0] === indata[pxPos] && this._transColor[1] === indata[pxPos + 1] && this._transColor[2] === indata[pxPos + 2]) {
+            makeTrans = true;
+          }
+          if (makeTrans) {
+            for (var i = 0; i < 4; i++) {
+              indata[pxPos + i] = 0;
+            }
+          }
+        }
+      }
+    }
+    if (depth !== 8) {
+      if (depth === 16) {
+        outdata = new Buffer(width * height * 4);
+      }
+      //console.log("adjusting");
+      var maxOutSample = 255;
+      var maxInSample = Math.pow(2, depth) - 1;
+
+      for (var y = 0; y < height; y++) {
+        var pxRowPos = y * pxLineLength;
+
+        for (var x = 0; x < width; x++) {
+          var pxPos = pxRowPos + (x << 2);
+          for (var i = 0; i < 4; i++)
+            outdata[pxPos + i] = Math.floor((indata[pxPos + i] * maxOutSample) / maxInSample + 0.5);
+        }
       }
     }
   }
-  return data;
+  return outdata;
 };
 
diff --git a/test/test.js b/test/test.js
index ac2ab5f..805ba76 100644
--- a/test/test.js
+++ b/test/test.js
@@ -7,7 +7,7 @@ fs.readdir(__dirname + '/in/', function(err, files) {
 
     files.forEach(function(file) {
 
-        if (!file.match(/.*\.png$/i))
+        if (!file.match(/\.png$/i))
             return;
 
         var expectedError = false;