require(hyperSpec)
spc <- read.spe("paracetamol.SPE")
baseline <- spc.rubberband(spc)

corrected <- spc - baseline

import numpy as np
from scipy.spatial import ConvexHull

def rubberband(x, y):
    # Find the convex hull
    v = ConvexHull(np.array(zip(x, y))).vertices

# Rotate convex hull vertices until they start from the lowest one
    v = np.roll(v, -v.argmin())
    # Leave only the ascending part
    v = v[:v.argmax()]

    # Create baseline using linear interpolation between vertices
    return np.interp(x, x[v], y[v])

y = y - rubberband(x, y)