diff --git a/lib/bitmapper.js b/lib/bitmapper.js
index 217da6a..2591b95 100644
--- a/lib/bitmapper.js
+++ b/lib/bitmapper.js
@@ -96,6 +96,45 @@ function bitRetriever(data, depth) {
   };
 }
 
+function mapImage8Bit(image, pxData, getPxPos, bpp, data, rawPos) { // eslint-disable-line max-params
+  var imageWidth = image.width;
+  var imageHeight = image.height;
+  var imagePass = image.index;
+  for (var y = 0; y < imageHeight; y++) {
+    for (var x = 0; x < imageWidth; x++) {
+      var pxPos = getPxPos(x, y, imagePass);
+
+      for (var i = 0; i < 4; i++) {
+        var idx = pixelBppMap[bpp][i];
+        if (i === data.length) {
+          throw new Error('Ran out of data');
+        }
+        pxData[pxPos + i] = idx !== 0xff ? data[idx + rawPos] : 0xff;
+      }
+      rawPos += bpp; //eslint-disable-line no-param-reassign
+    }
+  }
+  return rawPos;
+}
+
+function mapImageCustomBit(image, pxData, getPxPos, bpp, bits, maxBit) { // eslint-disable-line max-params
+  var imageWidth = image.width;
+  var imageHeight = image.height;
+  var imagePass = image.index;
+  for (var y = 0; y < imageHeight; y++) {
+    for (var x = 0; x < imageWidth; x++) {
+      var pixelData = bits.get(bpp);
+      var pxPos = getPxPos(x, y, imagePass);
+
+      for (var i = 0; i < 4; i++) {
+        var idx = pixelBppMap[bpp][i];
+        pxData[pxPos + i] = idx !== 0xff ? pixelData[idx] : maxBit;
+      }
+    }
+    bits.resetAfterLine();
+  }
+}
+
 exports.dataToBitMap = function(data, width, height, bpp, depth, interlace) {
 
   if (depth !== 8) {
@@ -110,7 +149,6 @@ exports.dataToBitMap = function(data, width, height, bpp, depth, interlace) {
   }
   var maxBit = Math.pow(2, depth) - 1;
   var rawPos = 0;
-  var pixelData;
   var images;
   var getPxPos;
 
@@ -129,34 +167,11 @@ exports.dataToBitMap = function(data, width, height, bpp, depth, interlace) {
   }
 
   for (var imageIndex = 0; imageIndex < images.length; imageIndex++) {
-    var imageWidth = images[imageIndex].width;
-    var imageHeight = images[imageIndex].height;
-    var imagePass = images[imageIndex].index;
-    for (var y = 0; y < imageHeight; y++) {
-      for (var x = 0; x < imageWidth; x++) {
-        if (depth !== 8) {
-          pixelData = bits.get(bpp);
-        }
-        var pxPos = getPxPos(x, y, imagePass);
-        //console.log(x,y,imageIndex, pxPos);
-        for (var i = 0; i < 4; i++) {
-          var idx = pixelBppMap[bpp][i];
-          if (depth === 8) {
-            if (i === data.length) {
-              throw new Error('Ran out of data');
-            }
-            pxData[pxPos + i] = idx !== 0xff ? data[idx + rawPos] : maxBit;
-          }
-          else {
-            pxData[pxPos + i] = idx !== 0xff ? pixelData[idx] : maxBit;
-          }
-        }
-        //console.log("R", pxData[pxPos], "G", pxData[pxPos + 1], "B", pxData[pxPos + 2], "A", pxData[pxPos + 3]);
-        rawPos += bpp;
-      }
-      if (depth !== 8) {
-        bits.resetAfterLine();
-      }
+    if (depth === 8) {
+      rawPos = mapImage8Bit(images[imageIndex], pxData, getPxPos, bpp, data, rawPos);
+    }
+    else {
+      mapImageCustomBit(images[imageIndex], pxData, getPxPos, bpp, bits, maxBit);
     }
   }
   if (depth === 8) {