#!/usr/bin/env python # -*- coding: utf-8 -*- # https://en.wikipedia.org/wiki/SRGB (The reverse transformation) def lin(c): return 100 * ((c/12.92) if (c<=0.04045) else pow((c+0.055)/1.055, 2.4)) import sys sys.stdout.write("#include \n") sys.stdout.write("const int8_t lab_table[196608] = {\n") # 65536 * 3 for i in range(65536): r = ((((i >> 3) & 31) * 255) + 15.5) // 31 g = (((((i & 7) << 3) | (i >> 13)) * 255) + 31.5) // 63 b = ((((i >> 8) & 31) * 255) + 15.5) // 31 # https://en.wikipedia.org/wiki/SRGB (The reverse transformation) r_lin = lin(r / 255.0) g_lin = lin(g / 255.0) b_lin = lin(b / 255.0) x = (r_lin * 0.4124) + (g_lin * 0.3576) + (b_lin * 0.1805); y = (r_lin * 0.2126) + (g_lin * 0.7152) + (b_lin * 0.0722); z = (r_lin * 0.0193) + (g_lin * 0.1192) + (b_lin * 0.9505); # https://en.wikipedia.org/wiki/Lab_color_space (CIELAB-CIEXYZ conversions) def f(t): return pow(t, (1/3.0)) if (t>0.008856) else ((7.787037*t)+0.137931) x = f(x / 095.047) y = f(y / 100.000) z = f(z / 108.883) l = int(round(116 * y)) - 16; a = int(round(500 * (x-y))); b = int(round(200 * (y-z))); sys.stdout.write(" %4d, %4d, %4d" % (l, a, b)) if (i + 1) % 4: sys.stdout.write(", ") elif i != 65535: sys.stdout.write(",\n") else: sys.stdout.write("\n};\n") sys.stdout.write("const float xyz_table[256] = {\n") for i in range(256): if not (i % 8): sys.stdout.write(" ") sys.stdout.write("%9.6ff" % lin(i / 255.0)) if (i + 1) % 8: sys.stdout.write(", ") elif i != 255: sys.stdout.write(",\n") else: sys.stdout.write("\n};\n")