public static Dictionary <String, int> CalculateKerning(char[] charSet, GLFontGlyph[] glyphs, List <GLFontBitmap> bitmapPages, GLFontKerningConfiguration config)
{
var kerningPairs = new Dictionary <String, int>();
//we start by computing the index of the first and last non-empty pixel in each row of each glyph
XLimits[][] limits = new XLimits[charSet.Length][];
int maxHeight = 0;
for (int n = 0; n < charSet.Length; n++)
{
var rect = glyphs[n].Rect;
var page = bitmapPages[glyphs[n].Page];
limits[n] = new XLimits[rect.Height];
maxHeight = Math.Max(rect.Height, maxHeight);
int yStart = rect.Y;
int yEnd = rect.Y + rect.Height;
int xStart = rect.X;
int xEnd = rect.X + rect.Width;
for (int j = yStart; j < yEnd; j++)
{
int last = xStart;
bool yetToFindFirst = true;
for (int i = xStart; i < xEnd; i++)
{
if (!GLFontBitmap.EmptyAlphaPixel(page.bitmapData, i, j, config.AlphaEmptyPixelTolerance))
{
if (yetToFindFirst)
{
limits[n][j - yStart].Min = i - xStart;
yetToFindFirst = false;
}
last = i;
}
}
limits[n][j - yStart].Max = last - xStart;
if (yetToFindFirst)
{
limits[n][j - yStart].Min = xEnd - 1;
}
}
}
//we now bring up each row to the max (or min) of it's two adjacent rows, this is to stop glyphs sliding together too closely
var tmp = new XLimits[maxHeight];
for (int n = 0; n < charSet.Length; n++)
{
//clear tmp
for (int j = 0; j < limits[n].Length; j++)
{
tmp[j] = limits[n][j];
}
for (int j = 0; j < limits[n].Length; j++)
{
if (j != 0)
{
tmp[j].Min = Math.Min(limits[n][j - 1].Min, tmp[j].Min);
tmp[j].Max = Math.Max(limits[n][j - 1].Max, tmp[j].Max);
}
if (j != limits[n].Length - 1)
{
tmp[j].Min = Math.Min(limits[n][j + 1].Min, tmp[j].Min);
tmp[j].Max = Math.Max(limits[n][j + 1].Max, tmp[j].Max);
}
}
for (int j = 0; j < limits[n].Length; j++)
{
limits[n][j] = tmp[j];
}
}
for (int i = 0; i < charSet.Length; i++)
{
for (int j = 0; j < charSet.Length; j++)
{
kerningPairs.Add("" + charSet[i] + charSet[j], 1 - Kerning(glyphs[i], glyphs[j], limits[i], limits[j], config));
}
}
return(kerningPairs);
}
private static int Kerning(GLFontGlyph g1, GLFontGlyph g2, XLimits[] lim1, XLimits[] lim2, GLFontKerningConfiguration config)
{
int yOffset1 = g1.YOffset;
int yOffset2 = g2.YOffset;
int startY = Math.Max(yOffset1, yOffset2);
int endY = Math.Min(g1.Rect.Height + yOffset1, g2.Rect.Height + yOffset2);
int w1 = g1.Rect.Width;
int worstCase = w1;
//TODO - offset startY, endY by yOffset1 so that lim1[j-yOffset1] can be written as lim1[j], will need another var for yOffset2
for (int j = startY; j < endY; j++)
{
worstCase = Math.Min(worstCase, w1 - lim1[j - yOffset1].Max + lim2[j - yOffset2].Min);
}
worstCase = Math.Min(worstCase, g1.Rect.Width);
worstCase = Math.Min(worstCase, g2.Rect.Width);
//modify by character kerning rules
GLFontCharacterKerningRule kerningRule = config.GetOverridingCharacterKerningRuleForPair("" + g1.Character + g2.Character);
if (kerningRule == GLFontCharacterKerningRule.Zero)
{
return(0);
}
else if (kerningRule == GLFontCharacterKerningRule.NotMoreThanHalf)
{
return((int)Math.Min(Math.Min(g1.Rect.Width, g2.Rect.Width) * 0.5f, worstCase));
}
return(worstCase);
}
