Question

need some help with this one. I have some reflectance values for a colour and need to convert these to L* a* b* C* h values.

I have found some visual basic source that claims to do this but I have no knowledge of visual basic to convert it into C sharp.

Anyone able to help?

http://www.vbforums.com/showthread.php?p=821074

Sample Data
Reflectance Values : 0.35380, 0.44130, 0.50230, 0.51650, 0.52210, 0.52780, 0.53110, 0.53350, 0.53630, 0.53900, 0.54130, 0.54330, 0.54500, 0.54630, 0.54690, 0.54680, 0.54640, 0.54710, 0.54940, 0.55240, 0.55330, 0.55250, 0.55200, 0.55190, 0.55220, 0.55310, 0.55260, 0.55340, 0.55500, 0.55540, 0.55400

Answer 1

I have managed to answer my own question!

double[] d65Vals_X = new double[31] { 0.137, 0.676, 1.603, 2.451, 3.418, 3.699, 3.064, 1.933, 0.802, 0.156, 0.039, 0.347, 1.070, 2.170, 3.397, 4.732, 6.070, 7.311, 8.291, 8.634, 8.672, 7.930, 6.446, 4.669, 3.095, 1.859, 1.056, 0.570, 0.274, .0121, 0.058 };
        double[] d65Vals_Y = new double[31] { 0.014, 0.069, 0.168, 0.300, 0.554, 0.890, 1.290, 1.838, 2.520, 3.226, 4.320, 5.621, 6.907, 8.059, 8.668, 8.855, 8.581, 7.951, 7.106, 6.004, 5.079, 4.065, 2.999, 2.042, 1.290, 0.746, 0.417, 0.223, 0.107, 0.047, 0.023 };
        double[] d65Vals_Z = new double[31] { 0.612, 3.110, 7.627, 12.095, 17.537, 19.888, 17.695, 13.000, 7.699, 3.938, 2.046, 1.049, 0.544, 0.278, 0.122, 0.035, 0.001, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000 };

        private double FXYZ(double[] REF, int A){
            double XYZref = 0;
            double illXYZ = 0;
            int i;

            for (i = 0; i < 31; i++)
            {
                if (A == 0){
                    XYZref = XYZref + (REF[i] * d65Vals_X[i]);
                    illXYZ = illXYZ + d65Vals_X[i];
                } else if (A == 1){
                    XYZref = XYZref + (REF[i] * d65Vals_Y[i]);
                    illXYZ = illXYZ + d65Vals_Y[i];
                } else {
                    XYZref = XYZref + (REF[i] * d65Vals_Z[i]);
                    illXYZ = illXYZ + d65Vals_Z[i];
                }                
            }
            return (XYZref / (100 * illXYZ));
        }
        private void btnCalculate_Click(object sender, EventArgs e)
        {
            int i;

            double L, A, B;

            double[] reflexVals = new double[31];
            Console.Write("Reflex Data: ");
            for (i = 0; i < 31; i++)
            {
                TextBox reflex = this.Controls["txtReflex_" + (i + 1)] as TextBox;                
                reflexVals[i] = double.Parse(reflex.Text);
                Console.Write(reflexVals[i].ToString() + ", ");
            }
            Console.Write("\n");

            double[] FFXYZ = new double[3];
            double[] XYZ = new double[3];
            double CR = (1 / 3);
            CR = 0.33333333333333333333333333333333;
            for (i = 0; i < 3; i++)
            {
                XYZ[i] = FXYZ(reflexVals, i);
                Console.WriteLine("XYZ[" + i + "] = " + XYZ[i]);
                if (XYZ[i] > 0.008856)
                {

                    FFXYZ[i] = Math.Pow(XYZ[i], CR);
                    Console.WriteLine("FFXYZ[" + i + "] = " + Math.Pow(XYZ[i], CR));
                }
                else
                {
                    FFXYZ[i] = (7.787 * XYZ[i]) + (16 / 116);
                    Console.WriteLine("FFXYZ[" + i + "] = (7.787 * " + XYZ[i] + ") + (16 / 116)");
                }
            }

            if (XYZ[1] > 0.00856)
            {
                L = (116 * FFXYZ[1]) - 16;
                Console.WriteLine("L = (116 * " + FFXYZ[1] + ") - 16");
            }
            else
            {
                L = 903.3 * XYZ[1];
                Console.WriteLine("L = 903.3 * " + XYZ[1] + ")");
            }

            A = 500 * (FFXYZ[0] - FFXYZ[1]);
            B = 200 * (FFXYZ[1] - FFXYZ[2]);

            Console.WriteLine("A = 500 * (" + FFXYZ[0] + " - " + FFXYZ[1] + ")");
            Console.WriteLine("A = 200 * (" + FFXYZ[1] + " - " + FFXYZ[2] + ")");

            txtCalcL.Text = L.ToString();
            txtCalcA.Text = A.ToString();
            txtCalcB.Text = B.ToString();
        }