public static float GetDistanceSq(LABColor c1, LABColor c2)
{
float da = c2.af - c1.af;
float db = c2.bf - c1.bf;
return(da * da + db * db);
}
public static LABColor[] PickKMeansCentroids(int numCentroids, LABColor[] dataPoints)
{
LABColor[] centroids = new LABColor[numCentroids];
//Use K-means++ to choose initial centroid values
//Choose one center uniformly at random from among the data points.
centroids[0] = dataPoints[(int)(rand.NextDouble() * numCentroids)];
//For each data point x, compute D(x), the distance between x and the nearest center that has already been chosen.
float highestD = 0;
int highestDIndex = 0;
float[] D = new float[dataPoints.Length];
for (int d = 0; d < dataPoints.Length; ++d)
{
D[d] = GetDistanceSq(centroids[0], dataPoints[d]);
if (D[d] > highestD)
{
highestD = D[d];
highestDIndex = d;
}
}
//Choose one new data point at random as a new center, using a weighted probability distribution where a point x is chosen with probability proportional to D(x)^2.
//Repeat until k centers have been chosen.
//Note: for now, just choose the datapoint with highest D
for (int c = 1; c < centroids.Length; ++c)
{
centroids[c] = dataPoints[highestDIndex];
//recalculate D's
highestD = 0;
highestDIndex = 0;
for (int d = 0; d < dataPoints.Length; ++d)
{
float currD = GetDistanceSq(centroids[c], dataPoints[d]);
if (currD < D[d])
{
D[d] = currD;
if (D[d] > highestD)
{
highestD = D[d];
highestDIndex = d;
}
}
}
}
return(centroids);
}
public static LABColor[] GenerateRandomLABColors(int numColors)
{
LABColor[] colors = new LABColor[numColors];
for (int i = 0; i < numColors; ++i)
{
colors[i] = new LABColor();
colors[i].Lf = (float)rand.NextDouble() * 100f;
colors[i].af = -128f + (float)rand.NextDouble() * 256f;
colors[i].bf = -128f + (float)rand.NextDouble() * 256f;
}
return(colors);
}
public static LABColor[] GetLABPixelData(Bitmap bmp)
{
LABColor[] labPixelData = new LABColor[bmp.Width * bmp.Height];
FastBitmap fastBmp = new FastBitmap(bmp);
fastBmp.LockImage();
for (int i = 0; i < labPixelData.Length; ++i)
{
labPixelData[i] = RGBToLAB(fastBmp.GetPixel());
fastBmp.NextPixel();
}
fastBmp.UnlockImage();
return(labPixelData);
}
public static LABColor RGBToLAB(Color rgb)
{
LABColor labColor = new LABColor();
// RGB to XYZ
// http://www.brucelindbloom.com/index.html?Eqn_RGB_to_XYZ.html
//Normalize rgb to [0,1]
float Vr = rgb.R / 255f;
float Vg = rgb.G / 255f;
float Vb = rgb.B / 255f;
//Inverse sRGB Companding
// (sRGB (V) to linear RGB (v))
float vr = Vr;
float vg = Vg;
float vb = Vb;
if (vr <= 0.04045)
{
vr = vr / 12.92f;
}
else
{
vr = (float)Math.Pow((vr + 0.055) / 1.055, 2.4);
}
if (vg <= 0.04045)
{
vg = vg / 12.92f;
}
else
{
vg = (float)Math.Pow((vg + 0.055) / 1.055, 2.4);
}
if (vb <= 0.04045)
{
vb = vb / 12.92f;
}
else
{
vb = (float)Math.Pow((vb + 0.055) / 1.055, 2.4);
}
// Linear RGB to XYZ
// [X,Y,Z] = [M][v]
// [M]: sRGB to XYZ matrix (with D50 ref white):
//http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html
float X = 0.4360747f * vr + 0.3850649f * vg + 0.1430804f * vb;
float Y = 0.2225045f * vr + 0.7168786f * vg + 0.0606169f * vb;
float Z = 0.0139322f * vr + 0.0971045f * vg + 0.7141733f * vb;
// XYZ to Lab
// http://www.brucelindbloom.com/index.html?Eqn_XYZ_to_Lab.html
float xr = X / Xr;
float yr = Y / Yr;
float zr = Z / Zr;
float fx, fy, fz;
if (xr > epsilon)
{
fx = (float)Math.Pow(xr, 1 / 3f);
}
else
{
fx = (k * xr + 16f) / 116f;
}
if (yr > epsilon)
{
fy = (float)Math.Pow(yr, 1 / 3f);
}
else
{
fy = (k * yr + 16f) / 116f;
}
if (zr > epsilon)
{
fz = (float)Math.Pow(zr, 1 / 3f);
}
else
{
fz = (k * zr + 16f) / 116f;
}
labColor.Lf = (116 * fy) - 16;
labColor.af = 500 * (fx - fy);
labColor.bf = 200 * (fy - fz);
return(labColor);
}
public static Color LABToRGB(LABColor lab)
{
int R, G, B;
// Lab to XYZ
// http://www.brucelindbloom.com/index.html?Eqn_Lab_to_XYZ.html
float fy = (lab.Lf + 16) / 116;
float fz = fy - (lab.bf / 200);
float fx = (lab.af / 500) + fy;
float xr = (float)Math.Pow(fx, 3);
float yr;
float zr = (float)Math.Pow(fz, 3);
if (!(xr > epsilon))
{
xr = (116 * fx - 16) / k;
}
if (lab.Lf > (k * epsilon))
{
yr = (float)Math.Pow((lab.Lf + 16) / 116, 3);
}
else
{
yr = lab.Lf / k;
}
if (!(zr > epsilon))
{
xr = (116 * fz - 16) / k;
}
float X = xr * Xr;
float Y = yr * Yr;
float Z = zr * Zr;
// XYZ to RGB
// http://www.brucelindbloom.com/index.html?Eqn_XYZ_to_RGB.html
// XYZ to Linear RGB (v)
// [v] = [M]^-1[X,Y,Z]
// [M]^-1: XYZ to sRGB matrix (with D50 ref white):
// http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html
float vr = 3.1338561f * X - 1.6168667f * Y - 0.4906146f * Z;
float vg = -0.9787684f * X + 1.9161415f * Y + 0.0334540f * Z;
float vb = 0.0719453f * X - 0.2289914f * Y + 1.4052427f * Z;
// sRGB Companding
// (linear RGB (v) to sRGB (V))
float Vr, Vg, Vb;
if (vr <= 0.0031308)
{
Vr = 12.92f * vr;
}
else
{
Vr = 1.055f * (float)Math.Pow(vr, 1 / 2.4f) - 0.055f;
}
if (vg <= 0.0031308)
{
Vg = 12.92f * vg;
}
else
{
Vg = 1.055f * (float)Math.Pow(vg, 1 / 2.4f) - 0.055f;
}
if (vb <= 0.0031308)
{
Vb = 12.92f * vb;
}
else
{
Vb = 1.055f * (float)Math.Pow(vb, 1 / 2.4f) - 0.055f;
}
//Normalize rgb to [0,255]
R = (int)(Vr * 255);
G = (int)(Vg * 255);
B = (int)(Vb * 255);
if (R > 255)
{
R = 255;
}
else if (R < 0)
{
R = 0;
}
if (G > 255)
{
G = 255;
}
else if (G < 0)
{
G = 0;
}
if (B > 255)
{
B = 255;
}
else if (B < 0)
{
B = 0;
}
return(Color.FromArgb(255, R, G, B));
}
