/// <summary>
/// Marks a color space tag.
/// </summary>
/// <param name="cube">The cube.</param>
/// <param name="label">A label.</param>
private void Mark(ColorRange cube, byte label)
{
for (int r = cube.R0 + 1; r <= cube.R1; r++)
{
for (int g = cube.G0 + 1; g <= cube.G1; g++)
{
for (int b = cube.B0 + 1; b <= cube.B1; b++)
{
tag[GetIndex(r, g, b)] = label;
}
}
}
}
/// <summary>
/// Builds the cube.
/// </summary>
/// <param name="colorCount">The color count.</param>
private ColorRange[] BuildCube(ref int colorCount)
{
var cube = new ColorRange[colorCount];
double[] vv = new double[colorCount];
for (int i = 0; i < colorCount; i++)
{
cube[i] = new ColorRange();
}
cube[0].R0 = cube[0].G0 = cube[0].B0 = 0;
cube[0].R1 = cube[0].G1 = cube[0].B1 = IndexCount - 1;
int next = 0;
for (int i = 1; i < colorCount; i++)
{
if (Cut(cube[next], cube[i]))
{
vv[next] = cube[next].Volume > 1 ? Variance(cube[next]) : 0.0;
vv[i] = cube[i].Volume > 1 ? Variance(cube[i]) : 0.0;
}
else
{
vv[next] = 0.0;
i--;
}
next = 0;
double temp = vv[0];
for (int k = 1; k <= i; k++)
{
if (vv[k] > temp)
{
temp = vv[k];
next = k;
}
}
if (temp <= 0.0)
{
colorCount = i + 1;
break;
}
}
return(cube);
}
/// <summary>
/// We want to minimize the sum of the variances of two sub-boxes.
/// The sum(c^2) terms can be ignored since their sum over both sub-boxes
/// is the same (the sum for the whole box) no matter where we split.
/// The remaining terms have a minus sign in the variance formula,
/// so we drop the minus sign and maximize the sum of the two terms.
/// </summary>
/// <param name="cube">The cube.</param>
/// <param name="direction">The direction.</param>
/// <param name="first">The first position.</param>
/// <param name="last">The last position.</param>
/// <param name="cut">The cutting point.</param>
/// <param name="wholeR">The whole red.</param>
/// <param name="wholeG">The whole green.</param>
/// <param name="wholeB">The whole blue.</param>
/// <param name="wholeW">The whole weight.</param>
/// <returns>The result.</returns>
private double Maximize(ColorRange cube, int direction, int first, int last, out int cut, double wholeR, double wholeG, double wholeB, double wholeW)
{
long baseR = Bottom(cube, direction, vmr);
long baseG = Bottom(cube, direction, vmg);
long baseB = Bottom(cube, direction, vmb);
long baseW = Bottom(cube, direction, vwt);
double max = 0.0;
cut = -1;
for (int i = first; i < last; i++)
{
double halfR = baseR + Top(cube, direction, i, vmr);
double halfG = baseG + Top(cube, direction, i, vmg);
double halfB = baseB + Top(cube, direction, i, vmb);
double halfW = baseW + Top(cube, direction, i, vwt);
if (halfW == 0)
{
continue;
}
double temp = ((halfR * halfR) + (halfG * halfG) + (halfB * halfB)) / halfW;
halfR = wholeR - halfR;
halfG = wholeG - halfG;
halfB = wholeB - halfB;
halfW = wholeW - halfW;
if (halfW == 0)
{
continue;
}
temp += ((halfR * halfR) + (halfG * halfG) + (halfB * halfB)) / halfW;
if (temp > max)
{
max = temp;
cut = i;
}
}
return(max);
}
/// <summary>
/// Computes the weighted variance of a box.
/// </summary>
/// <param name="cube">The cube.</param>
/// <returns>The result.</returns>
private double Variance(ColorRange cube)
{
double dr = Volume(cube, vmr);
double dg = Volume(cube, vmg);
double db = Volume(cube, vmb);
double xx = m2[GetIndex(cube.R1, cube.G1, cube.B1)]
- m2[GetIndex(cube.R1, cube.G1, cube.B0)]
- m2[GetIndex(cube.R1, cube.G0, cube.B1)]
+ m2[GetIndex(cube.R1, cube.G0, cube.B0)]
- m2[GetIndex(cube.R0, cube.G1, cube.B1)]
+ m2[GetIndex(cube.R0, cube.G1, cube.B0)]
+ m2[GetIndex(cube.R0, cube.G0, cube.B1)]
- m2[GetIndex(cube.R0, cube.G0, cube.B0)];
return(xx - (((dr * dr) + (dg * dg) + (db * db)) / Volume(cube, vwt)));
}
/// <summary>
/// Cuts a box.
/// </summary>
/// <param name="set1">The first set.</param>
/// <param name="set2">The second set.</param>
/// <returns>Returns a value indicating whether the box has been split.</returns>
private bool Cut(ColorRange set1, ColorRange set2)
{
double wholeR = Volume(set1, vmr);
double wholeG = Volume(set1, vmg);
double wholeB = Volume(set1, vmb);
double wholeW = Volume(set1, vwt);
int cutr;
int cutg;
int cutb;
double maxr = Maximize(set1, 2, set1.R0 + 1, set1.R1, out cutr, wholeR, wholeG, wholeB, wholeW);
double maxg = Maximize(set1, 1, set1.G0 + 1, set1.G1, out cutg, wholeR, wholeG, wholeB, wholeW);
double maxb = Maximize(set1, 0, set1.B0 + 1, set1.B1, out cutb, wholeR, wholeG, wholeB, wholeW);
int dir;
if ((maxr >= maxg) && (maxr >= maxb))
{
dir = 2;
if (cutr < 0)
{
return(false);
}
}
else if ((maxg >= maxr) && (maxg >= maxb))
{
dir = 1;
}
else
{
dir = 0;
}
set2.R1 = set1.R1;
set2.G1 = set1.G1;
set2.B1 = set1.B1;
switch (dir)
{
// Red
case 2:
set2.R0 = set1.R1 = cutr;
set2.G0 = set1.G0;
set2.B0 = set1.B0;
break;
// Green
case 1:
set2.G0 = set1.G1 = cutg;
set2.R0 = set1.R0;
set2.B0 = set1.B0;
break;
// Blue
case 0:
set2.B0 = set1.B1 = cutb;
set2.R0 = set1.R0;
set2.G0 = set1.G0;
break;
}
set1.Volume = (set1.R1 - set1.R0) * (set1.G1 - set1.G0) * (set1.B1 - set1.B0);
set2.Volume = (set2.R1 - set2.R0) * (set2.G1 - set2.G0) * (set2.B1 - set2.B0);
return(true);
}
