Lens Blur node

[harisreedhar]

Add lens blur node

[RunDevelopment]

Thank you for the PR @harisreedhar!

I looked through your code and have a few suggestions.
Also, please format the new code with black.

[RunDevelopment]

@joeyballentine Does opencv or numpy include scipy?

[joeyballentine]

@RunDevelopment I don't think so, so that means we would need to add that as another dependency. It's actually required by facexlib so anyone who has the pytorch deps installed already has it.

[harisreedhar]

@RunDevelopment I don't think so, so that means we would need to add that as another dependency. It's actually required by facexlib so anyone who has the pytorch deps installed already has it.

scipy.signal.convolve2d can be replaced with this function. So no need to add extra dependency.

def conv2d(a, f):
    s = f.shape + tuple(np.subtract(a.shape, f.shape) + 1)
    strd = np.lib.stride_tricks.as_strided
    subM = strd(a, shape = s, strides = a.strides * 2)
    return np.einsum('ij,ijkl->kl', f, subM)

EDIT: Above function produces small square blocks in image. not same as scipy.signal :(

[RunDevelopment]

Maybe we could use cv2.filter2D? That one also does a convolution.

[harisreedhar]

Maybe we could use cv2.filter2D? That one also does a convolution.

Found gimp lens blur filter using cv2.filter2D. It is faster than current implementation

[RunDevelopment]

It is faster than current implementation

Holy, it's waaay faster. Nice! My little test example dropped from 51s to 4.3s, so it's over 10x faster.