message: added constants
diff: @@ -2798,19 +2798,13 @@ def psnr(a, b, max_val, name=None):
  with ops.control_dependencies(checks):
  return array_ops.identity(psnr_val)
  -_SSIM_K1 = 0.01
  -_SSIM_K2 = 0.03
  -_SSIM_FILTER_SIZE = 11
  -_SSIM_SIGMA = 1.5
  -
  -
  def _ssim_helper(x,
  y,
  reducer,
  max_val,
  compensation=1.0,
  - k1=_SSIM_K1,
  - k2=_SSIM_K2):
  + k1=0.01,
  + k2=0.03):
  r"""Helper function for computing SSIM.
  SSIM estimates covariances with weighted sums. The default parameters
  @@ -2889,10 +2883,10 @@ def _fspecial_gauss(size, sigma):
  def _ssim_per_channel(img1,
  img2,
  max_val=1.0,
  - filter_size=_SSIM_FILTER_SIZE,
  - filter_sigma=_SSIM_SIGMA,
  - k1=_SSIM_K1,
  - k2=_SSIM_K2):
  + filter_size=11,
  + filter_sigma=1.5,
  + k1=0.01,
  + k2=0.03):
  """Computes SSIM index between img1 and img2 per color channel.
  This function matches the standard SSIM implementation from:
  @@ -2968,10 +2962,10 @@ def _ssim_per_channel(img1,
  def ssim(img1,
  img2,
  max_val,
  - filter_size=_SSIM_FILTER_SIZE,
  - filter_sigma=_SSIM_SIGMA,
  - k1=_SSIM_K1,
  - k2=_SSIM_K2):
  + filter_size=11,
  + filter_sigma=1.5,
  + k1=0.01,
  + k2=0.03):
  """Computes SSIM index between img1 and img2.
  This function is based on the standard SSIM implementation from:
  @@ -3012,8 +3006,8 @@ def ssim(img1,
  img2: Second image batch.
  max_val: The dynamic range of the images (i.e., the difference between the
  maximum the and minimum allowed values).
  - filter_size: size of gaussian filter.
  - filter_sigma: width of gaussian filter.
  + filter_size: Default value 11 (size of gaussian filter).
  + filter_sigma: Default value 1.5 (width of gaussian filter).
  k1: Default value 0.01
  k2: Default value 0.03 (SSIM is less sensitivity to K2 for
  lower values, so it would be better if we taken the values in range
  @@ -3049,10 +3043,10 @@ def ssim_multiscale(img1,
  img2,
  max_val,
  power_factors=_MSSSIM_WEIGHTS,
  - filter_size=_SSIM_FILTER_SIZE,
  - filter_sigma=_SSIM_SIGMA,
  - k1=_SSIM_K1,
  - k2=_SSIM_K2):
  + filter_size=11,
  + filter_sigma=1.5,
  + k1=0.01,
  + k2=0.03):
  """Computes the MS-SSIM between img1 and img2.
  This function assumes that `img1` and `img2` are image batches, i.e. the last
  