--- a/nes.py
+++ b/nes.py
@@ -7,36 +7,42 @@
 
 
 class NES_ROM(object):
-    def __init__(self, filename):
+    def __init__(self, filename=None, initial_position=0, palettes=None):
         self.filename = filename
 
         # To track circular rotation of the PRG bytes, in case the
         # tiles aren't aligned to 16-byte boundaries and the user
         # moves it.
-        self.initial_position = 0
-        self.read_rom()
+        self.initial_position = initial_position
+
+        self.parse_rom(palettes)
 
-    def read_rom(self):
-        if self.filename.lower().endswith('.nes'):
-            with open(self.filename, 'rb') as rom:
-                self.ines = rom.read()
-        elif self.filename.lower().endswith('.zip'):
+    @staticmethod
+    def read_ines(filename):
+        if filename.lower().endswith('.nes'):
+            with open(filename, 'rb') as rom:
+                ines = rom.read()
+        elif filename.lower().endswith('.zip'):
             try:
-                with ZipFile(self.filename, 'r') as rom:
+                with ZipFile(filename, 'r') as rom:
                     nesfiles = [f for f in rom.filelist if not f.is_dir()
                                 and f.filename.lower().endswith(".nes")]
                     if len(nesfiles) != 1:
                         raise ROMOpeningError(
                             "Zipfile does not contain exactly one NES file"
                         )
-                    self.ines = rom.open(nesfiles[0]).read()
+                    ines = rom.open(nesfiles[0]).read()
             except BadZipFile as exc:
                 raise ROMOpeningError(f"Problem opening zip file:\n{exc}")
         else:
             raise ROMOpeningError(
                 f"Cannot deduce file type from file name:\n\n"
-                f"{self.filename.split('/')[-1]}"
+                f"{filename.split('/')[-1]}"
             )
+        return ines
+
+    def parse_rom(self, palettes):
+        self.ines = self.read_ines(self.filename)
 
         self.header = self.ines[0:16]
         body = self.ines[16:]
@@ -44,6 +50,7 @@
         CHR_size = self.header[5]*8192
 
         self.PRG = body[0:PRG_size]
+
         if CHR_size == 0:
             # No chr, just read the whole ROM as tiles
             self.CHR = None
@@ -52,8 +59,18 @@
             self.CHR = body[PRG_size:PRG_size+CHR_size]
             self.tile_data = list(self.CHR)
 
-        self.tiles = [Tile(idx, self.tile_data)
-                      for idx in range(0, len(self.tile_data)//16)]
+        self.rotate_tile_data(self.initial_position)
+
+        numtiles = len(self.tile_data)//16
+        if not palettes:
+            palettes = [None]*numtiles
+        elif len(palettes) != numtiles:
+            raise ValueError(
+                "JSON data does not contain the same amount of tile palattes as tiles in ROM"
+            )
+
+        self.tiles = [Tile(idx, self.tile_data, palette=palette)
+                      for (idx, palette) in enumerate(palettes)]
 
     def update_tiles(self):
         for tile in self.tiles: