/// <summary>
/// Uploads the mip0 stored in the Content to the Texture2D and generates new mips.
/// </summary>
public unsafe void UploadContentToTexture()
{
GL.BindTexture(TextureTarget.Texture2D, Texture);
var data = Content.Pin();
GL.TexImage2D(TextureTarget.Texture2D, 0,
srgb ? PixelInternalFormat.Rgba8Snorm : PixelInternalFormat.Rgba8,
Content.Width, Content.Height, 0,
PixelFormat.Rgba, PixelType.UnsignedByte,
new IntPtr(data + Content.GetMipStartIndex(0))
);
Content.Unpin();
GL.GenerateMipmap(GenerateMipmapTarget.Texture2D);
GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)TextureMinFilter.LinearMipmapLinear);
GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)TextureMagFilter.Linear);
GL.BindTexture(TextureTarget.Texture2D, 0);
}
public unsafe static FontContent Build(Stream fontDataStream)
{
var faceBytes = new byte[fontDataStream.Length];
fontDataStream.Read(faceBytes, 0, faceBytes.Length);
using (var library = new Library())
{
using (var face = new Face(library, faceBytes, 0))
{
//Collect glyph boundings information.
face.SetPixelSizes(FontSizeInPixels, FontSizeInPixels);
var sortedCharacterSet = new char[characterSet.Length];
var sortedCharacterData = new CharacterData[characterSet.Length];
for (int i = 0; i < characterSet.Length; ++i)
{
sortedCharacterSet[i] = characterSet[i];
face.LoadGlyph(face.GetCharIndex(characterSet[i]), LoadFlags.Default, LoadTarget.Normal);
ref var characterData = ref sortedCharacterData[i];
characterData.SourceSpan.X = face.Glyph.Metrics.Width.ToInt32();
characterData.SourceSpan.Y = face.Glyph.Metrics.Height.ToInt32();
characterData.Bearing.X = face.Glyph.Metrics.HorizontalBearingX.ToInt32();
characterData.Bearing.Y = face.Glyph.Metrics.HorizontalBearingY.ToInt32();
characterData.Advance = face.Glyph.Metrics.HorizontalAdvance.ToInt32();
}
//Next, allocate space in the atlas for each character.
//Sort the characters by height, and then scan from one side of the atlas to the other placing characters.
//Once the other side is reached, flip directions and repeat. Continue until no more characters remain.
Array.Sort(sortedCharacterData, sortedCharacterSet, new CharacterHeightComparer());
const int padding = 1 << MipLevels;
var characters = new Dictionary <char, CharacterData>();
var packer = new FontPacker(AtlasWidth, MipLevels, padding, characterSet.Length);
for (int i = 0; i < sortedCharacterSet.Length; ++i)
{
//The packer class handles the placement logic and sets the SourceMinimum in the character data, too.
packer.Add(ref sortedCharacterData[i]);
}
//Now that every glyph has been positioned within the sheet, we can actually rasterize the glyph alphas into a bitmap proto-atlas.
//We're building the rasterized set sequentially first so we don't have to worry about threading issues in the underlying library.
var rasterizedAlphas = new Texture2DContent(AtlasWidth, packer.Height, 1, 1);
for (int i = 0; i < sortedCharacterSet.Length; ++i)
{
//Rasterize the glyph.
var character = sortedCharacterSet[i];
face.LoadGlyph(face.GetCharIndex(character), LoadFlags.Default, LoadTarget.Normal);
face.Glyph.RenderGlyph(RenderMode.Normal);
//Copy the alphas into the pixel alpha buffer at the appropriate position.
int glyphWidth = face.Glyph.Bitmap.Width;
int glyphHeight = face.Glyph.Bitmap.Rows;
var glyphBuffer = (byte *)face.Glyph.Bitmap.Buffer;
Int2 location;
location.X = sortedCharacterData[i].SourceMinimum.X;
location.Y = sortedCharacterData[i].SourceMinimum.Y;
for (int glyphRow = 0; glyphRow < glyphHeight; ++glyphRow)
{
Unsafe.CopyBlockUnaligned(
ref rasterizedAlphas.Data[rasterizedAlphas.GetRowOffsetForMip0(glyphRow + location.Y) + location.X],
ref glyphBuffer[glyphRow * glyphWidth], (uint)glyphWidth);
}
}
//Preallocate memory for full single precision float version of the atlas. This will be used as scratch memory (admittedly, more than is necessary)
//which will be encoded into the final single byte representation after the mips are calculated. The full precision stage makes the mips a little more accurate.
var preciseAtlas = new Texture2DContent(AtlasWidth, packer.Height, MipLevels, 4);
var atlas = new Texture2DContent(AtlasWidth, packer.Height, MipLevels, 1);
//Compute the distances for every character-covered texel in the atlas.
var atlasData = atlas.Pin();
var preciseData = (float *)preciseAtlas.Pin();
var alphaData = rasterizedAlphas.Pin();
var pool = new PassthroughArrayPool <Int2>();
//for (int i = 0; i < sortedCharacterData.Length; ++i)
Parallel.For(0, sortedCharacterData.Length, i =>
{
//Note that the padding around characters should also have its distances filled in. That way, the less detailed mips can pull from useful data.
ref var charData = ref sortedCharacterData[i];
var min = new Int2(charData.SourceMinimum.X, charData.SourceMinimum.Y);
var max = new Int2(charData.SourceMinimum.X + charData.SourceSpan.X, charData.SourceMinimum.Y + charData.SourceSpan.Y);
var paddedMin = new Int2(min.X - padding, min.Y - padding);
var paddedMax = new Int2(max.X + padding, max.Y + padding);
//Initialize every character texel to max distance. The following BFS only ever reduces distances, so it has to start high.
var maxDistance = Math.Max(AtlasWidth, packer.Height);
for (int rowIndex = paddedMin.Y; rowIndex < paddedMax.Y; ++rowIndex)
{
var rowOffset = preciseAtlas.GetRowOffsetForMip0(rowIndex);
var distancesRow = preciseData + rowOffset;
for (int columnIndex = paddedMin.X; columnIndex < paddedMax.X; ++columnIndex)
{
distancesRow[columnIndex] = maxDistance;
}
}
//Scan the alphas. Add border texels of the glyph to the point set. We collect both the nonzero alpha outline and the 'negative space' zero alpha outline.
//While scanning distances, nonzero alpha texels will look for the shortest distance to a zero alpha texel, while zero alpha texels will look for the shortest
//distance to a nonzero alpha texel.
var glyphOutline = new List <Int2>((max.X - min.X) * (max.Y - min.Y));
int coverageThreshold = 127;
for (int rowIndex = min.Y; rowIndex < max.Y; ++rowIndex)
{
//Alphas and atlas have same dimensions, so sharing row offset is safe.
Debug.Assert(padding > 0, "This assumes at least one padding; no boundary checking is performed on the alpha accesses.");
var rowOffset = preciseAtlas.GetRowOffsetForMip0(rowIndex);
var alphasRow0 = alphaData + rowOffset - preciseAtlas.Width;
var alphasRow1 = alphaData + rowOffset;
var alphasRow2 = alphaData + rowOffset + preciseAtlas.Width;
for (int columnIndex = min.X; columnIndex < max.X; ++columnIndex)
{
if (alphasRow1[columnIndex] >= coverageThreshold)
{
//This texel is considered covered.
//Only add this to the point set if there is at least one adjacent uncovered texel.
//If there isn't an uncovered texel next to this one, then it can't be on the surface.
if (alphasRow0[columnIndex] < coverageThreshold ||
alphasRow1[columnIndex - 1] < coverageThreshold ||
alphasRow1[columnIndex + 1] < coverageThreshold ||
alphasRow2[columnIndex] < coverageThreshold)
{
Int2 texelCoordinates;
texelCoordinates.X = columnIndex;
texelCoordinates.Y = rowIndex;
glyphOutline.Add(texelCoordinates);
}
}
}
}
//For every texel in the character's region, scan the glyph point set for the nearest texel.
//Cache the largest distance as we go so that we can maximize precision within this character.
float largestDistanceMagnitude = 0;
for (int rowIndex = paddedMin.Y; rowIndex < paddedMax.Y; ++rowIndex)
{
var rowOffset = preciseAtlas.GetRowOffsetForMip0(rowIndex); //Same dimensions; can be shared.
var distancesRow = preciseData + rowOffset;
var alphasRow = alphaData + rowOffset;
for (int columnIndex = paddedMin.X; columnIndex < paddedMax.X; ++columnIndex)
{
//This is an uncovered texel. Look for a glyph outline.
float lowestDistance = float.MaxValue;
for (int pointIndex = 0; pointIndex < glyphOutline.Count; ++pointIndex)
{
var point = glyphOutline[pointIndex];
var offsetX = point.X - columnIndex;
var offsetY = point.Y - rowIndex;
var candidateDistance = (float)Math.Sqrt(offsetX * offsetX + offsetY * offsetY);
if (candidateDistance < lowestDistance)
{
lowestDistance = candidateDistance;
}
}
//If it's uncovered, use a positive distance. If it's covered, use a negative distance.
distancesRow[columnIndex] = alphasRow[columnIndex] < coverageThreshold ? lowestDistance : -lowestDistance;
if (lowestDistance > largestDistanceMagnitude)
{
largestDistanceMagnitude = lowestDistance;
}
}
}
//Build the mips. We already have all the data in cache on this core; 256KiB L2 can easily hold the processing context of a 128x128 glyph.
//(Though worrying about performance in the content builder too much is pretty silly. We aren't going to be building fonts often.)
//Note that we aligned and padded each glyph during packing. For a given texel in mip(n), the four parent texels in mip(n-1) can be safely sampled.
for (int mipLevel = 1; mipLevel < preciseAtlas.MipLevels; ++mipLevel)
{
var mipMin = new Int2(paddedMin.X >> mipLevel, paddedMin.Y >> mipLevel);
var mipMax = new Int2(paddedMax.X >> mipLevel, paddedMax.Y >> mipLevel);
//Yes, these do some redundant calculations, but no it doesn't matter.
var parentMipStart = preciseData + preciseAtlas.GetMipStartIndex(mipLevel - 1);
var parentMipRowPitch = preciseAtlas.GetRowPitch(mipLevel - 1);
var mipStart = preciseData + preciseAtlas.GetMipStartIndex(mipLevel);
var mipRowPitch = preciseAtlas.GetRowPitch(mipLevel);
for (int mipRowIndex = mipMin.Y; mipRowIndex < mipMax.Y; ++mipRowIndex)
{
var mipRow = mipStart + mipRowIndex * mipRowPitch;
var parentRowIndex = mipRowIndex << 1;
var parentMipRow0 = parentMipStart + parentRowIndex * parentMipRowPitch;
var parentMipRow1 = parentMipStart + (parentRowIndex + 1) * parentMipRowPitch;
for (int mipColumnIndex = mipMin.X; mipColumnIndex < mipMax.X; ++mipColumnIndex)
{
var parentMipColumnIndex0 = mipColumnIndex << 1;
var parentMipColumnIndex1 = parentMipColumnIndex0 + 1;
mipRow[mipColumnIndex] = 0.25f * (
parentMipRow0[parentMipColumnIndex0] + parentMipRow0[parentMipColumnIndex1] +
parentMipRow1[parentMipColumnIndex0] + parentMipRow1[parentMipColumnIndex1]);
}
}
}
//Now that all mips have been filled, bake the data into the final single byte encoding.
//Use the largest absolute distance as the encoding multiplier to maximize precision.
charData.DistanceScale = largestDistanceMagnitude;
var encodingMultiplier = 1f / largestDistanceMagnitude;
for (int mipLevel = 0; mipLevel < atlas.MipLevels; ++mipLevel)
{
var mipMin = new Int2(paddedMin.X >> mipLevel, paddedMin.Y >> mipLevel);
var mipMax = new Int2(paddedMax.X >> mipLevel, paddedMax.Y >> mipLevel);
//Note signed bytes. We're building an R8_SNORM texture, not UNORM.
var encodedStart = (sbyte *)atlasData + atlas.GetMipStartIndex(mipLevel);
var preciseStart = preciseData + preciseAtlas.GetMipStartIndex(mipLevel);
var rowPitch = atlas.GetRowPitch(mipLevel);
for (int rowIndex = mipMin.Y; rowIndex < mipMax.Y; ++rowIndex)
{
var preciseRow = preciseStart + rowIndex * rowPitch;
var encodedRow = encodedStart + rowIndex * rowPitch;
for (int columnIndex = mipMin.X; columnIndex < mipMax.X; ++columnIndex)
{
encodedRow[columnIndex] = (sbyte)(127 * Math.Max(-1, Math.Min(1, encodingMultiplier * preciseRow[columnIndex])));
}
}
}
});