Here you can find the source of rgb2luv(double[] rgb, double[] luv)
| Parameter | Description |
|---|---|
| rgb | Color components in the sRGB color space. |
| luv | Optional array for storing color components in the CIE L*u*v color space. |
public static double[] rgb2luv(double[] rgb, double[] luv)
//package com.java2s; //License from project: Open Source License public class Main { /**// w w w .j a va 2 s . com * Constant for the CIE XYZ and CIE L*u*v* color spaces: (6/29)^3 * */ private static final double CIE_EPSILON = 216.0 / 24389.0; /** * Constant for the CIE XYZ and CIE L*u*v* color spaces: (29/3)^3 * */ private static final double CIE_KAPPA = 24389.0 / 27.0; /** * Xr, Yr, Zr constants with D50 white point used for CIE XYZ to * CIE L*u*v* conversion * */ private static final double[] XYZ_R_D50 = { 0.964221, 1.000000, 0.825211 }; /** * sRGB to CIE XYZ conversion matrix. See * http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html#Specifications * * */ private static final double[] MATRIX_SRGB2XYZ_D50 = { 0.436052025, 0.385081593, 0.143087414, 0.222491598, 0.716886060, 0.060621486, 0.013929122, 0.097097002, 0.714185470 }; /** * Converts color components from the CIE L*u*v* to the sRGB color space. * A D50 white point is assumed for the sRGB conversion. If the <i>luv</i> * array is {@code null}, a new one will be created with the same * size as the <i>rgb</i> array. * * @param rgb Color components in the sRGB color space. * @param luv Optional array for storing color components in the CIE L*u*v* * color space. * @return Color components in the CIE L*u*v* color space. */ public static double[] rgb2luv(double[] rgb, double[] luv) { double[] xyz = rgb2xyz(rgb, null); return xyz2luv(xyz, luv); } /** * Converts color components from the sRGB to the CIE XYZ color space. * A D50 white point is assumed for the sRGB conversion. If the <i>xyz</i> * array is {@code null}, a new one will be created with the same * size as the <i>rgb</i> array. * * See http://www.brucelindbloom.com/index.html?Eqn_RGB_to_XYZ.html * * @param rgb Color components in the sRGB color space. * @param xyz Optional array to store color components in the CIE XYZ color * space. * @return Color components in the CIE XYZ color space. */ public static double[] rgb2xyz(double[] rgb, double[] xyz) { if (xyz == null) { xyz = new double[rgb.length]; } // Remove sRGB companding to make RGB components linear double[] rgbLin = new double[rgb.length]; for (int i = 0; i < rgb.length; i++) { if (rgb[i] <= 0.04045) { rgbLin[i] = rgb[i] / 12.92; } else { rgbLin[i] = Math.pow((rgb[i] + 0.055) / 1.055, 2.4); } } // Convert linear sRGB with D50 white point to CIE XYZ for (int i = 0; i < xyz.length; i++) { xyz[i] = MATRIX_SRGB2XYZ_D50[i * 3 + 0] * rgbLin[0] + MATRIX_SRGB2XYZ_D50[i * 3 + 1] * rgbLin[1] + MATRIX_SRGB2XYZ_D50[i * 3 + 2] * rgbLin[2]; } return xyz; } /** * Converts color components from the CIE XYZ to the CIE L*u*v* color * space. If the <i>luv</i> array is {@code null}, a new one will be * created with the same size as the <i>xyz</i> array. * * http://www.brucelindbloom.com/index.html?Eqn_XYZ_to_Luv.html * * @param xyz Color components in the CIE XYZ color space. * @param luv Optional array for storing color components in the CIE L*u*v* * color space. * @return Color components in the CIE L*u*v* color space. */ public static double[] xyz2luv(double[] xyz, double[] luv) { double tmp = xyz[0] + 15.0 * xyz[1] + 3.0 * xyz[2]; if (tmp == 0.0) { tmp = 1.0; } double u1 = 4.0 * xyz[0] / tmp; double v1 = 9.0 * xyz[1] / tmp; // Relative luminance double yr = xyz[1] / XYZ_R_D50[1]; double ur = 4.0 * XYZ_R_D50[0] / (XYZ_R_D50[0] + 15.0 * XYZ_R_D50[1] + 3.0 * XYZ_R_D50[2]); double vr = 9.0 * XYZ_R_D50[1] / (XYZ_R_D50[0] + 15.0 * XYZ_R_D50[1] + 3.0 * XYZ_R_D50[2]); // Mapping relative luminance to lightness if (luv == null) { luv = new double[xyz.length]; } if (yr > CIE_EPSILON) { luv[0] = 116.0 * Math.pow(yr, 1.0 / 3.0) - 16.0; } else { luv[0] = CIE_KAPPA * yr; } luv[1] = 13.0 * luv[0] * (u1 - ur); luv[2] = 13.0 * luv[0] * (v1 - vr); return luv; } }