old_contents: from PyQt4 import QtGui
  import qimage2ndarray, numpy, os
  from ..alpha import verified_unblend
  
  def imread(filename):
      filename = os.path.join(os.path.dirname(__file__), filename)
      return qimage2ndarray.rgb_view(QtGui.QImage(filename))
  
  def color(r, g, b):
      return numpy.array([r, g, b], numpy.uint8)
  
  # --------------------------------------------------------------------
  
  def _check_alpha(alpha, max_neg_diff = 0, max_pos_diff = 0):
      expected_alpha = 255 - imread('test_on_white.png')[...,0]
      diff = (alpha - expected_alpha).view(numpy.int8)
      assert diff.min() >= max_neg_diff
      assert diff.max() <= max_pos_diff
  
  
  def test_black_on_white():
      rgb = imread('test_on_white.png')
      bg = color(255, 255, 255)
      c = color(0, 0, 0)
      alpha = verified_unblend(rgb, bg, c)
      assert alpha is not None
      assert alpha.dtype == numpy.uint8
      _check_alpha(alpha, -1)
  
  
  def test_white_on_black():
      rgb = imread('test_alpha.png')
      bg = color(0, 0, 0)
      c = color(255, 255, 255)
      alpha = verified_unblend(rgb, bg, c)
      assert alpha is not None
      _check_alpha(alpha)
  
  
  def test_black_on_bg():
      rgb = imread('test_on_bg.png')
      bg = imread('test_bg.png')
      c = color(0, 0, 0)
      alpha = verified_unblend(rgb, bg, c)
      assert alpha is not None
      _check_alpha(alpha, -4, 1)
  
  
  def test_green_on_bg():
      rgb = imread('test_on_bg2.png')
      bg = imread('test_bg.png')
      c = color(181, 255, 64)
      alpha = verified_unblend(rgb, bg, c)
      assert alpha is not None
      _check_alpha(alpha, -1)
  
new_contents: from PyQt4 import QtGui
  import qimage2ndarray, numpy, os
  from ..alpha import verified_unblend
  
  def imread(filename):
      filename = os.path.join(os.path.dirname(__file__), filename)
      return qimage2ndarray.rgb_view(QtGui.QImage(filename))
  
  def color(r, g, b):
      return numpy.array([r, g, b], numpy.uint8)
  
  # --------------------------------------------------------------------
  
  def _check_alpha(alpha, max_neg_diff = 0, max_pos_diff = 0):
      assert alpha is not None
      assert alpha.dtype == numpy.uint8
      expected_alpha = 255 - imread('test_on_white.png')[...,0]
      diff = (alpha - expected_alpha).view(numpy.int8)
      assert diff.min() >= max_neg_diff
      assert diff.max() <= max_pos_diff
  
  
  def test_black_on_white():
      rgb = imread('test_on_white.png')
      bg = color(255, 255, 255)
      c = color(0, 0, 0)
      alpha = verified_unblend(rgb, bg, c)
      _check_alpha(alpha, -1)
  
  
  def test_white_on_black():
      rgb = imread('test_alpha.png')
      bg = color(0, 0, 0)
      c = color(255, 255, 255)
      alpha = verified_unblend(rgb, bg, c)
      _check_alpha(alpha)
  
  
  def test_black_on_bg():
      rgb = imread('test_on_bg.png')
      bg = imread('test_bg.png')
      c = color(0, 0, 0)
      alpha = verified_unblend(rgb, bg, c)
      _check_alpha(alpha, -4, 1)
  
  
  def test_green_on_bg():
      rgb = imread('test_on_bg2.png')
      bg = imread('test_bg.png')
      c = color(181, 255, 64)
      alpha = verified_unblend(rgb, bg, c)
      _check_alpha(alpha, -1)
  
subject: reduce duplicated code