Total Reflectance from Human Skin

Scott Prahl

Nov 2021

version 1

Test the ability to grab an arbitrary sample from the 100 available.

The paper is available at

Reference Data Set of Human Skin Reflectance

The data is available at

The Data Set

import numpy as np
import matplotlib.pyplot as plt

import iadpython.nist

%config InlineBackend.figure_format='retina'

subject_number = 5

λ,R1,R2,R3,_ = iadpython.nist.subject_reflectances(subject_number)
plt.plot(λ,R1)
plt.plot(λ,R2)

plt.plot(λ,R3)


plt.xlabel("Wavelength (nm)")
plt.ylabel("Total Reflectance")
plt.title("Subject #%d" % subject_number)
plt.show()

subject_number = 5

λ,R = iadpython.nist.subject_average_reflectance(subject_number)
plt.plot(λ,R)
plt.xlabel("Wavelength (nm)")
plt.ylabel("Total Reflectance")
plt.title("Subject #%d" % subject_number)
plt.show()

λ,R = iadpython.nist.all_average_reflectances()

for i in range(100):
    plt.plot(λ,R[:,i]-np.min(R[:,i]))

plt.xlabel("Wavelength (nm)")
plt.ylabel("Total Reflectance")
plt.title("All Subjects")
plt.show()

λ,R = iadpython.nist.all_average_reflectances()

j = np.abs(λ-800).argmin()

R_near_800nm = R[j,:]

R = np.sort(R_near_800nm)

plt.plot(R, 'o', markersize=1)

plt.xlabel("Subject")
plt.ylabel("Total Reflectance")
plt.title("Reflectance at 800nm")
plt.show()

def dawson_melanin(λ,R):

    L = -np.log(R)

    j700 = np.abs(λ-700).argmin()
    j650 = np.abs(λ-650).argmin()

    M = 100 * (L[j650] - L[j700] + 0.015)

    return M

def kollias_melanin(λ,R):

    L = -np.log(R)

    j720 = np.abs(λ-700).argmin()
    j620 = np.abs(λ-650).argmin()

    C2, C1 = np.polyfit(λ[j620:j720],L[j620:j720],1)
#    linear_model_fn=np.poly1d([C2,C1])
#    fitted = linear_model_fn(λ)
#    print(linear_model)

#    plt.xlim(400,800)
#    plt.plot(λ,L)
#    plt.plot(λ,fitted)
#    plt.show()
    return C1, C2

λ,R = iadpython.nist.subject_average_reflectance(25)

kollias_melanin(λ,R)

(1.301623639826864, -0.0011112599552051414)

λ,R = iadpython.nist.all_average_reflectances()

L = -np.log(R)

j700 = np.abs(λ-700).argmin()
j650 = np.abs(λ-650).argmin()

M = 100 * (L[j650] - L[j700] + 0.015)

plt.plot(λ,L)

plt.xlim(500,800)
plt.ylim(0,2.5)
plt.axvspan(620,720,color='cyan',alpha=0.5)

plt.xlabel("Subject")
plt.ylabel("Total Reflectance")
plt.title("Reflectance at 800nm")
plt.show()

λ,R = iadpython.nist.all_average_reflectances()

c = np.array([])
m = np.array([])
for i in range(100):
    c1, c2 = kollias_melanin(λ, R[:,i])
    m1 = dawson_melanin(λ, R[:,i])
    c = np.append(c, c1)
    m = np.append(m, m1)

csort = np.sort(c)
plt.title("NIST Skin Reflectance Database")
plt.plot(csort, 'bo',markersize=2)
plt.xlabel("Increase Subject Pigmentation")
plt.ylabel("Kollias Melanin Metric")
plt.show()

λ,R = iadpython.nist.all_average_reflectances()

c = np.array([])
m = np.array([])
for i in range(100):
    c1, c2 = kollias_melanin(λ, R[:,i])
    m1 = dawson_melanin(λ, R[:,i])
    c = np.append(c, c1)
    m = np.append(m, m1)

plt.title("NIST Skin Reflectance Database")
plt.plot(c, m, 'bo',markersize=2)
plt.ylabel("Dawson Melanin Metric")

plt.xlabel("Kollias Melanin Metric")
plt.show()