This patch unifies the variable size blur between the CPU and GPU
compositor. The difference is due to how weights are computed and used.
The CPU computed a nested array of weights for every possible size, that
is, from size 1 to the base size. Then, it assumed the kernel was
separable and reconstructed a 2D kernel by selecting two 1D weights
array and multiplying them for every pixel of the blur window.
The GPU on the other hand computes a single quadrant of the 2D weights
kernel and sampled it directly in the blur window. We favor the GPU
implementation since it makes no assumptions about the separability of
the weights kernel and since the CPU has no performance advantage even
with the assumption in place.
Pull Request: https://projects.blender.org/blender/blender/pulls/118834
56f8c1c0f6