FAILURE CASE: This case fails to preserve the white upper part of the
cow. The source image had a white sky and a green ground. Because of
how the boundary pixels are handled by the blending algorithm, this
results in a green gradient across the cow.
Here we have a shark fin in the water. This result blends well, due to
the similarity of the background colors of the source and target images.
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The same target image does not work as well for this ship, due to the
differences in the background of the source image.