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Fixed division by zero bug in alpha compositing

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This commit is contained in:
Sridhar Ramesh
2018-02-20 12:33:58 -08:00
parent 652dab7f23
commit c2b9417c6a
2 changed files with 19 additions and 3 deletions
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7
camera/camera.py
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@ -430,10 +430,15 @@ class Camera(object):
] ]
out_a = src_a + dst_a*(1.0-src_a) out_a = src_a + dst_a*(1.0-src_a)
# When the output alpha is 0 for full transparency,
# we have a choice over what RGB value to use in our
# output representation. We choose 0.0 here.
out_rgb = fdiv( out_rgb = fdiv(
src_rgb*src_a[..., None] + \ src_rgb*src_a[..., None] + \
dst_rgb*dst_a[..., None]*(1.0-src_a[..., None]), dst_rgb*dst_a[..., None]*(1.0-src_a[..., None]),
out_a[..., None] out_a[..., None],
zero_over_zero_value = 0.0
) )
self.pixel_array[..., :3] = out_rgb*self.rgb_max_val self.pixel_array[..., :3] = out_rgb*self.rgb_max_val

15
helpers.py
View File

@ -694,8 +694,19 @@ class DictAsObject(object):
self.__dict__ = dict self.__dict__ = dict
# Just to have a less heavyweight name for this extremely common operation # Just to have a less heavyweight name for this extremely common operation
def fdiv(a, b): #
return np.true_divide(a,b) # We may wish to have more fine-grained control over division by zero behavior
# in future (separate specifiable default values for 0/0 and x/0 with x != 0),
# but for now, we just allow the option to handle 0/0.
def fdiv(a, b, zero_over_zero_value = None):
if zero_over_zero_value != None:
out = np.full_like(a, zero_over_zero_value)
where = np.logical_or (a != 0, b != 0)
else:
out = None
where = True
return np.true_divide(a, b, out = out, where = where)
def add_extension_if_not_present(file_name, extension): def add_extension_if_not_present(file_name, extension):
# This could conceivably be smarter about handling existing differing extensions # This could conceivably be smarter about handling existing differing extensions