/// <summary>
/// 指定された単色ビットマップ画像をDXT3テクスチャへ変換する
/// </summary>
/// <param name="source">変換元画像</param>
/// <param name="color0">単色カラー</param>
/// <returns>DXT3圧縮された画像</returns>
public static Dxt3BitmapContent Compress(PixelBitmapContent<Color> source,
Color color0)
{
// DXT3ブロックデータを格納するためのバッファを確保
byte[] outputData = new byte[source.Width * source.Height];
// 単色カラーをBGR565に変換する
ushort packedColor = new Bgr565(color0.ToVector3()).PackedValue;
// 指定された画像を圧縮ブロック単位に処理をする
int outputIndex = 0;
for (int blockY = 0; blockY < source.Height; blockY += 4)
{
for (int blockX = 0; blockX < source.Width; blockX += 4)
{
CompressDxt3Block(source, blockX, blockY, packedColor,
outputData, outputIndex);
outputIndex += 16;
}
}
// DXT3テクスチャの生成と圧縮したブロックデータの設定
var result = new Dxt3BitmapContent(source.Width, source.Height);
result.SetPixelData(outputData);
return result;
}
// Compress the greyscale font texture page using a specially-formulated DXT3 mode
static public unsafe void CompressFontDXT3(TextureContent content)
{
if (content.Faces.Count > 1)
{
throw new PipelineException("Font textures should only have one face");
}
var block = new Vector4[16];
for (int i = 0; i < content.Faces[0].Count; ++i)
{
var face = content.Faces[0][i];
var xBlocks = (face.Width + 3) / 4;
var yBlocks = (face.Height + 3) / 4;
var dxt3Size = xBlocks * yBlocks * 16;
var buffer = new byte[dxt3Size];
var bytes = face.GetPixelData();
fixed(byte *b = bytes)
{
Vector4 *colors = (Vector4 *)b;
int w = 0;
int h = 0;
int x = 0;
int y = 0;
while (h < (face.Height & ~3))
{
w = 0;
x = 0;
var h0 = h * face.Width;
var h1 = h0 + face.Width;
var h2 = h1 + face.Width;
var h3 = h2 + face.Width;
while (w < (face.Width & ~3))
{
block[0] = colors[w + h0];
block[1] = colors[w + h0 + 1];
block[2] = colors[w + h0 + 2];
block[3] = colors[w + h0 + 3];
block[4] = colors[w + h1];
block[5] = colors[w + h1 + 1];
block[6] = colors[w + h1 + 2];
block[7] = colors[w + h1 + 3];
block[8] = colors[w + h2];
block[9] = colors[w + h2 + 1];
block[10] = colors[w + h2 + 2];
block[11] = colors[w + h2 + 3];
block[12] = colors[w + h3];
block[13] = colors[w + h3 + 1];
block[14] = colors[w + h3 + 2];
block[15] = colors[w + h3 + 3];
int offset = (x + y * xBlocks) * 16;
CompressFontDXT3Block(block, buffer, offset);
w += 4;
++x;
}
// Do partial block at end of row
if (w < face.Width)
{
var cols = face.Width - w;
Array.Clear(block, 0, 16);
for (int r = 0; r < 4; ++r)
{
h0 = (h + r) * face.Width;
for (int c = 0; c < cols; ++c)
{
block[(r * 4) + c] = colors[w + h0 + c];
}
}
int offset = (x + y * xBlocks) * 16;
CompressFontDXT3Block(block, buffer, offset);
}
h += 4;
++y;
}
// Do last partial row
if (h < face.Height)
{
var rows = face.Height - h;
w = 0;
x = 0;
while (w < (face.Width & ~3))
{
Array.Clear(block, 0, 16);
for (int r = 0; r < rows; ++r)
{
var h0 = (h + r) * face.Width;
block[(r * 4) + 0] = colors[w + h0 + 0];
block[(r * 4) + 1] = colors[w + h0 + 1];
block[(r * 4) + 2] = colors[w + h0 + 2];
block[(r * 4) + 3] = colors[w + h0 + 3];
}
int offset = (x + y * xBlocks) * 16;
CompressFontDXT3Block(block, buffer, offset);
w += 4;
++x;
}
// Do last partial block
if (w < face.Width)
{
var cols = face.Width - w;
Array.Clear(block, 0, 16);
for (int r = 0; r < rows; ++r)
{
var h0 = (h + r) * face.Width;
for (int c = 0; c < cols; ++c)
{
block[(r * 4) + c] = colors[w + h0 + c];
}
}
int offset = (x + y * xBlocks) * 16;
CompressFontDXT3Block(block, buffer, offset);
}
}
}
var dxt3 = new Dxt3BitmapContent(face.Width, face.Height);
dxt3.SetPixelData(buffer);
content.Faces[0][i] = dxt3;
}
}
