ulab 2x, 3x image upscaling in CircuitPython

code_2x.py

# Double size upscaling of an array by @v923z 
import ulab

n = 4 # input size, the thermal sensor is 8x8
b = ulab.array(range(n * n)).reshape((n, n)) # dummy data for testing
a = ulab.zeros((2*n-1, 2*n-1)) # the upscaled image

# Some magic by @v923z
a[::2,::2] = b
a[1::2,::2] = 0.5 * (b[:-1,:] + b[1:, :])

if False: # Solution by @v923z potentially more memory effective as it always take slice of b as source
    a[::2,1::2] = 0.5 * (b[:,1:] + b[:,:-1])
    a[1::2,1::2] = 0.25 * (b[:-1,1:] + b[1:,:-1] + b[1:,1:] + b[:-1,:-1])
else: # Alternative by @David.Glaude that is using two view of a to compute piece of a
    a[::,1::2]=0.5 * (a[::,:-1:2] + a[::,2::2])

print(b)
#array([[0.0, 1.0, 2.0, 3.0],
#       [4.0, 5.0, 6.0, 7.0],
#       [8.0, 9.0, 10.0, 11.0],
#       [12.0, 13.0, 14.0, 15.0]], dtype=float32)

print(a)
#array([[0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0],
#       [2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0],
#       [4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0],
#       [6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0],
#       [8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0],
#       [10.0, 10.5, 11.0, 11.5, 12.0, 12.5, 13.0],
#       [12.0, 12.5, 13.0, 13.5, 14.0, 14.5, 15.0]], dtype=float32)

code_3x.py

# Triple size upscaling of an array based on magic by @v923z 
import ulab

n = 2 # input size, the thermal sensor is 8x8
b = ulab.array(range(0, n * n * 3, 3)).reshape((n, n)) # dummy data for testing
a = ulab.zeros((3*n-2, 3*n-2)) # the upscaled image

a[::3,::3] = b
a[1::3,::3] = b[:-1,:] * (2/3) + b[1:, :] /3 
a[2::3,::3] = b[:-1,:] / 3 + b[1:, :] * (2/3) 
a[::,1::3] = a[::,:-1:3] * (2/3) + a[::,3::3] * (1/3) 
a[::,2::3] = a[::,:-1:3] * (1/3) + a[::,3::3] * (2/3) 

print(b)
#array([[0.0, 3.0],
#       [6.0, 9.0]], dtype=float32)

print(a)
#array([[0.0, 1.0, 2.0, 3.0],
#       [2.0, 3.0, 4.0, 5.0],
#       [4.0, 5.0, 6.0, 7.0],
#       [6.0, 7.0, 8.0, 9.0]], dtype=float32)

code_4x.py

# Quadruple size upscaling of an array based on magic by @v923z 
import ulab

n = 2 # input size, the thermal sensor is 8x8
b = ulab.array(range(0, n * n * 4, 4)).reshape((n, n)) # dummy data for testing
a = ulab.zeros((4*n-3, 4*n-3)) # the upscaled image

a[::4,::4] = b

a[1::4,::4] = b[:-1,:] * (3/4) + b[1:, :] * (1/4)
a[2::4,::4] = b[:-1,:] * (2/4) + b[1:, :] * (2/4)
a[3::4,::4] = b[:-1,:] * (1/4) + b[1:, :] * (3/4)

a[::,1::4] = a[::,:-1:4] * (3/4) + a[::,4::4] * (1/4) 
a[::,2::4] = a[::,:-1:4] * (2/4) + a[::,4::4] * (2/4) 
a[::,3::4] = a[::,:-1:4] * (1/4) + a[::,4::4] * (3/4) 

print(b)
#array([[0.0, 4.0],
#       [8.0, 12.0]], dtype=float32)

print(a)
#array([[0.0, 1.0, 2.0, 3.0, 4.0],
#       [2.0, 3.0, 4.0, 5.0, 6.0],
#       [4.0, 5.0, 6.0, 7.0, 8.0],
#       [6.0, 7.0, 8.0, 9.0, 10.0],
#       [8.0, 9.0, 10.0, 11.0, 12.0]], dtype=float32)