diff --git a/tools/releasetools/blockimgdiff.py b/tools/releasetools/blockimgdiff.py
index ecb1d31..72f065d 100644
--- a/tools/releasetools/blockimgdiff.py
+++ b/tools/releasetools/blockimgdiff.py
@@ -28,12 +28,12 @@
 import threading
 import zlib
 from collections import deque, namedtuple, OrderedDict
-from hashlib import sha1
 
 import common
+from images import EmptyImage
 from rangelib import RangeSet
 
-__all__ = ["EmptyImage", "DataImage", "BlockImageDiff"]
+__all__ = ["BlockImageDiff"]
 
 logger = logging.getLogger(__name__)
 
@@ -60,209 +60,6 @@
     return PatchInfo(imgdiff, f.read())
 
 
-class Image(object):
-  def RangeSha1(self, ranges):
-    raise NotImplementedError
-
-  def ReadRangeSet(self, ranges):
-    raise NotImplementedError
-
-  def TotalSha1(self, include_clobbered_blocks=False):
-    raise NotImplementedError
-
-  def WriteRangeDataToFd(self, ranges, fd):
-    raise NotImplementedError
-
-
-class EmptyImage(Image):
-  """A zero-length image."""
-
-  def __init__(self):
-    self.blocksize = 4096
-    self.care_map = RangeSet()
-    self.clobbered_blocks = RangeSet()
-    self.extended = RangeSet()
-    self.total_blocks = 0
-    self.file_map = {}
-    self.hashtree_info = None
-
-  def RangeSha1(self, ranges):
-    return sha1().hexdigest()
-
-  def ReadRangeSet(self, ranges):
-    return ()
-
-  def TotalSha1(self, include_clobbered_blocks=False):
-    # EmptyImage always carries empty clobbered_blocks, so
-    # include_clobbered_blocks can be ignored.
-    assert self.clobbered_blocks.size() == 0
-    return sha1().hexdigest()
-
-  def WriteRangeDataToFd(self, ranges, fd):
-    raise ValueError("Can't write data from EmptyImage to file")
-
-
-class DataImage(Image):
-  """An image wrapped around a single string of data."""
-
-  def __init__(self, data, trim=False, pad=False):
-    self.data = data
-    self.blocksize = 4096
-
-    assert not (trim and pad)
-
-    partial = len(self.data) % self.blocksize
-    padded = False
-    if partial > 0:
-      if trim:
-        self.data = self.data[:-partial]
-      elif pad:
-        self.data += '\0' * (self.blocksize - partial)
-        padded = True
-      else:
-        raise ValueError(("data for DataImage must be multiple of %d bytes "
-                          "unless trim or pad is specified") %
-                         (self.blocksize,))
-
-    assert len(self.data) % self.blocksize == 0
-
-    self.total_blocks = len(self.data) // self.blocksize
-    self.care_map = RangeSet(data=(0, self.total_blocks))
-    # When the last block is padded, we always write the whole block even for
-    # incremental OTAs. Because otherwise the last block may get skipped if
-    # unchanged for an incremental, but would fail the post-install
-    # verification if it has non-zero contents in the padding bytes.
-    # Bug: 23828506
-    if padded:
-      clobbered_blocks = [self.total_blocks-1, self.total_blocks]
-    else:
-      clobbered_blocks = []
-    self.clobbered_blocks = clobbered_blocks
-    self.extended = RangeSet()
-
-    zero_blocks = []
-    nonzero_blocks = []
-    reference = '\0' * self.blocksize
-
-    for i in range(self.total_blocks-1 if padded else self.total_blocks):
-      d = self.data[i*self.blocksize : (i+1)*self.blocksize]
-      if d == reference:
-        zero_blocks.append(i)
-        zero_blocks.append(i+1)
-      else:
-        nonzero_blocks.append(i)
-        nonzero_blocks.append(i+1)
-
-    assert zero_blocks or nonzero_blocks or clobbered_blocks
-
-    self.file_map = dict()
-    if zero_blocks:
-      self.file_map["__ZERO"] = RangeSet(data=zero_blocks)
-    if nonzero_blocks:
-      self.file_map["__NONZERO"] = RangeSet(data=nonzero_blocks)
-    if clobbered_blocks:
-      self.file_map["__COPY"] = RangeSet(data=clobbered_blocks)
-
-  def _GetRangeData(self, ranges):
-    for s, e in ranges:
-      yield self.data[s*self.blocksize:e*self.blocksize]
-
-  def RangeSha1(self, ranges):
-    h = sha1()
-    for data in self._GetRangeData(ranges): # pylint: disable=not-an-iterable
-      h.update(data)
-    return h.hexdigest()
-
-  def ReadRangeSet(self, ranges):
-    return list(self._GetRangeData(ranges))
-
-  def TotalSha1(self, include_clobbered_blocks=False):
-    if not include_clobbered_blocks:
-      return self.RangeSha1(self.care_map.subtract(self.clobbered_blocks))
-    return sha1(self.data).hexdigest()
-
-  def WriteRangeDataToFd(self, ranges, fd):
-    for data in self._GetRangeData(ranges): # pylint: disable=not-an-iterable
-      fd.write(data)
-
-
-class FileImage(Image):
-  """An image wrapped around a raw image file."""
-
-  def __init__(self, path, hashtree_info_generator=None):
-    self.path = path
-    self.blocksize = 4096
-    self._file_size = os.path.getsize(self.path)
-    self._file = open(self.path, 'rb')
-
-    if self._file_size % self.blocksize != 0:
-      raise ValueError("Size of file %s must be multiple of %d bytes, but is %d"
-                       % self.path, self.blocksize, self._file_size)
-
-    self.total_blocks = self._file_size // self.blocksize
-    self.care_map = RangeSet(data=(0, self.total_blocks))
-    self.clobbered_blocks = RangeSet()
-    self.extended = RangeSet()
-
-    self.generator_lock = threading.Lock()
-
-    self.hashtree_info = None
-    if hashtree_info_generator:
-      self.hashtree_info = hashtree_info_generator.Generate(self)
-
-    zero_blocks = []
-    nonzero_blocks = []
-    reference = '\0' * self.blocksize
-
-    for i in range(self.total_blocks):
-      d = self._file.read(self.blocksize)
-      if d == reference:
-        zero_blocks.append(i)
-        zero_blocks.append(i+1)
-      else:
-        nonzero_blocks.append(i)
-        nonzero_blocks.append(i+1)
-
-    assert zero_blocks or nonzero_blocks
-
-    self.file_map = {}
-    if zero_blocks:
-      self.file_map["__ZERO"] = RangeSet(data=zero_blocks)
-    if nonzero_blocks:
-      self.file_map["__NONZERO"] = RangeSet(data=nonzero_blocks)
-    if self.hashtree_info:
-      self.file_map["__HASHTREE"] = self.hashtree_info.hashtree_range
-
-  def __del__(self):
-    self._file.close()
-
-  def _GetRangeData(self, ranges):
-    # Use a lock to protect the generator so that we will not run two
-    # instances of this generator on the same object simultaneously.
-    with self.generator_lock:
-      for s, e in ranges:
-        self._file.seek(s * self.blocksize)
-        for _ in range(s, e):
-          yield self._file.read(self.blocksize)
-
-  def RangeSha1(self, ranges):
-    h = sha1()
-    for data in self._GetRangeData(ranges): # pylint: disable=not-an-iterable
-      h.update(data)
-    return h.hexdigest()
-
-  def ReadRangeSet(self, ranges):
-    return list(self._GetRangeData(ranges))
-
-  def TotalSha1(self, include_clobbered_blocks=False):
-    assert not self.clobbered_blocks
-    return self.RangeSha1(self.care_map)
-
-  def WriteRangeDataToFd(self, ranges, fd):
-    for data in self._GetRangeData(ranges): # pylint: disable=not-an-iterable
-      fd.write(data)
-
-
 class Transfer(object):
   def __init__(self, tgt_name, src_name, tgt_ranges, src_ranges, tgt_sha1,
                src_sha1, style, by_id):