diff --git a/lib/bitmapper.js b/lib/bitmapper.js
index 4ba5d76..e84111f 100644
--- a/lib/bitmapper.js
+++ b/lib/bitmapper.js
@@ -2,32 +2,107 @@
 
 var interlaceUtils = require('./interlace');
 
-var pixelBppMap = {
-  1: { // L
-    0: 0,
-    1: 0,
-    2: 0,
-    3: 0xff
+var pixelBppMapper = [
+  // 0 - dummy entry
+  function() {},
+
+  // 1 - L
+  // 0: 0, 1: 0, 2: 0, 3: 0xff
+  function(pxData, data, pxPos, rawPos) {
+    if (rawPos === data.length) {
+      throw new Error('Ran out of data');
+    }
+
+    var pixel = data[rawPos];
+    pxData[pxPos] = pixel;
+    pxData[pxPos + 1] = pixel;
+    pxData[pxPos + 2] = pixel;
+    pxData[pxPos + 3] = 0xff;
   },
-  2: { // LA
-    0: 0,
-    1: 0,
-    2: 0,
-    3: 1
+
+  // 2 - LA
+  // 0: 0, 1: 0, 2: 0, 3: 1
+  function(pxData, data, pxPos, rawPos) {
+    if (rawPos + 1 >= data.length) {
+      throw new Error('Ran out of data');
+    }
+
+    var pixel = data[rawPos];
+    pxData[pxPos] = pixel;
+    pxData[pxPos + 1] = pixel;
+    pxData[pxPos + 2] = pixel;
+    pxData[pxPos + 3] = data[rawPos + 1];
   },
-  3: { // RGB
-    0: 0,
-    1: 1,
-    2: 2,
-    3: 0xff
+
+  // 3 - RGB
+  // 0: 0, 1: 1, 2: 2, 3: 0xff
+  function(pxData, data, pxPos, rawPos) {
+    if (rawPos + 2 >= data.length) {
+      throw new Error('Ran out of data');
+    }
+
+    pxData[pxPos] = data[rawPos];
+    pxData[pxPos + 1] = data[rawPos + 1];
+    pxData[pxPos + 2] = data[rawPos + 2];
+    pxData[pxPos + 3] = 0xff;
   },
-  4: { // RGBA
-    0: 0,
-    1: 1,
-    2: 2,
-    3: 3
+
+  // 4 - RGBA
+  // 0: 0, 1: 1, 2: 2, 3: 3
+  function(pxData, data, pxPos, rawPos) {
+    if (rawPos + 3 >= data.length) {
+      throw new Error('Ran out of data');
+    }
+
+    pxData[pxPos] = data[rawPos];
+    pxData[pxPos + 1] = data[rawPos + 1];
+    pxData[pxPos + 2] = data[rawPos + 2];
+    pxData[pxPos + 3] = data[rawPos + 3];
   }
-};
+];
+
+var pixelBppCustomMapper = [
+  // 0 - dummy entry
+  function() {},
+
+  // 1 - L
+  // 0: 0, 1: 0, 2: 0, 3: 0xff
+  function(pxData, pixelData, pxPos, maxBit) {
+    var pixel = pixelData[0];
+    pxData[pxPos] = pixel;
+    pxData[pxPos + 1] = pixel;
+    pxData[pxPos + 2] = pixel;
+    pxData[pxPos + 3] = maxBit;
+  },
+
+  // 2 - LA
+  // 0: 0, 1: 0, 2: 0, 3: 1
+  function(pxData, pixelData, pxPos) {
+    var pixel = pixelData[0];
+    pxData[pxPos] = pixel;
+    pxData[pxPos + 1] = pixel;
+    pxData[pxPos + 2] = pixel;
+    pxData[pxPos + 3] = pixelData[1];
+  },
+
+  // 3 - RGB
+  // 0: 0, 1: 1, 2: 2, 3: 0xff
+  function(pxData, pixelData, pxPos, maxBit) {
+    pxData[pxPos] = pixelData[0];
+    pxData[pxPos + 1] = pixelData[1];
+    pxData[pxPos + 2] = pixelData[2];
+    pxData[pxPos + 3] = maxBit;
+  },
+
+  // 4 - RGBA
+  // 0: 0, 1: 1, 2: 2, 3: 3
+  function(pxData, pixelData, pxPos) {
+    pxData[pxPos] = pixelData[0];
+    pxData[pxPos + 1] = pixelData[1];
+    pxData[pxPos + 2] = pixelData[2];
+    pxData[pxPos + 3] = pixelData[3];
+  }
+];
 
 function bitRetriever(data, depth) {
 
@@ -102,19 +177,7 @@ function mapImage8Bit(image, pxData, getPxPos, bpp, data, rawPos) { // eslint-di
   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 (idx === 0xff) {
-          pxData[pxPos + i] = 0xff;
-        } else {
-          var dataPos = idx + rawPos;
-          if (dataPos === data.length) {
-            throw new Error('Ran out of data');
-          }
-          pxData[pxPos + i] = data[dataPos];
-        }
-      }
+      pixelBppMapper[bpp](pxData, data, pxPos, rawPos);
       rawPos += bpp; //eslint-disable-line no-param-reassign
     }
   }
@@ -129,11 +192,7 @@ function mapImageCustomBit(image, pxData, getPxPos, bpp, bits, maxBit) { // esli
     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;
-      }
+      pixelBppCustomMapper[bpp](pxData, pixelData, pxPos, maxBit);
     }
     bits.resetAfterLine();
   }