2018-10-03 18:59:01 +00:00
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# from: parakeet testbed
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# setup: import numpy as np ; M, N = 512, 512 ; I = np.random.randn(M,N)
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# run: harris(I)
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2018-04-05 22:07:33 +00:00
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2018-10-03 18:59:01 +00:00
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# pythran export harris(float64[][])
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2018-04-05 22:07:33 +00:00
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def harris(I):
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2018-10-03 18:59:01 +00:00
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m, n = I.shape
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dx = (I[1:, :] - I[:m - 1, :])[:, 1:]
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dy = (I[:, 1:] - I[:, :n - 1])[1:, :]
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2018-04-05 22:07:33 +00:00
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2018-10-03 18:59:01 +00:00
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#
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# At each point we build a matrix
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# of derivative products
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# M =
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# | A = dx^2 C = dx * dy |
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# | C = dy * dx B = dy * dy |
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#
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# and the score at that point is:
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# det(M) - k*trace(M)^2
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#
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A = dx * dx
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B = dy * dy
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C = dx * dy
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tr = A + B
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det = A * B - C * C
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k = 0.05
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return det - k * tr * tr
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