Obtain color with bilinear filtering on the CPU, equivalent to the default bilinear filtering on the GPU

bilinear_get_color.py

# type: (list, float, float) -> list
# img: the input image
# cx, cy: image coordinates in floats
def bilinear_get_color(img, cx, cy):
    x, y = [int(floor(cx)), int(ceil(cx))], [int(floor(cy)), int(ceil(cy))]
    u, v = cx - x[0], cy - y[0]
    r = np.zeros((2, 2, 3), np.uint8)
    w, h = len(img[0]), len(img)
    for i in range(2):
        for j in range(2):
            tx, ty = min(w - 1, max(0, x[i])), min(h - 1, max(0, y[j]))
            r[i][j] = img[ty][tx]
    return r[0][0] * (1 - u) * (1 - v) + r[0][1] * (1 - u) * v + r[1][0] * u * (1 - v) + r[1][1] * u * v