trilinear_interpolation.py

import numba
def FindLowAndHighIndices(x, m):
    xf = np.floor(x)
    

    l = np.clip(xf, 0, m-1).astype(int)
    h = np.clip(xf + 1, 0, m-1).astype(int)
    
    return l, h 

@numba.autojit
def TriLinearInterpolate(xa, ya, za, V):
    x0, x1 = FindLowAndHighIndices(xa, V.shape[0])
    y0, y1 = FindLowAndHighIndices(ya, V.shape[1])
    z0, z1 = FindLowAndHighIndices(za, V.shape[2])
    
    xDif, yDif, zDif = xa - x0, ya - y0, za - z0
    
    xd = (xa - x0) / (x1 - x0)
    yd = (ya - y0) / (y1 - y0)
    zd = (za - z0) / (z1 - z0)
    
    out = np.zeros([xa.shape[0], ya.shape[0],za.shape[0]])
    for ix, x in enumerate(xa):
        for iy, y in enumerate(ya):
            for iz, z in enumerate(za):
               
                if x1[ix] - x0[ix] == 0:
                    xd[ix] = 1
                if y1[iy] - y0[iy] == 0:
                    yd[iy] = 1
                if z1[iz] - z0[iz] == 0:
                    zd[iz] = 1
                    
                c00 = V[x0[ix], y0[iy], z0[iz]] * (1 - xd[ix])+ V[x1[ix], y0[iy], z0[iz]] * xd[ix]
                c01 = V[x0[ix], y0[iy], z1[iz]] * (1 - xd[ix])+ V[x1[ix], y0[iy], z1[iz]] * xd[ix]
                c10 = V[x0[ix], y1[iy], z0[iz]] * (1 - xd[ix])+ V[x1[ix], y1[iy], z0[iz]] * xd[ix]
                c11 = V[x0[ix], y1[iy], z1[iz]] * (1 - xd[ix])+ V[x1[ix], y1[iy], z1[iz]] * xd[ix]
    
                c0 = c00 * (1 - yd[iy]) + c10 * yd[iy]
                c1 = c01 * (1 - yd[iy]) + c11 * yd[iy]

                c = c0 * (1 - zd[iz]) + c1 * zd[iz]
                
                out[ix,iy,iz] = c
    return out

x = np.linspace(0, 600-1, 600//4)
y = np.linspace(0, 600-1, 600//4)
z = np.linspace(0, 3-1, 3)

im_pil = Image.open("/home/dulyanov/CROPPED-Lempitsky and Ulyanov 3.jpg")
im = np.array(im_pil)
im2 = TriLinearInterpolate(x,y,z, im)