public static TextureMipMapData[] GenerateMipMaps(
int width,
int height,
byte[] rgbaData)
{
var numLevels = CalculateMipMapCount(width, height);
var mipMapData = new TextureMipMapData[numLevels];
int previousWidth = -1, previousHeight = -1;
for (int level = 0; level < numLevels; level++)
{
if (level > 0)
{
var levelData = new byte[width * height * ByteRgba.BytesPerPixel];
for (int y = 0; y < height; y++)
{
for (int x = 0; x < width; x++)
{
int previousLevelX = x * (previousWidth / width);
int previousLevelY = y * (previousHeight / height);
var moreDetailedMipLevel = mipMapData[level - 1];
var c00 = ByteRgba.FromByteArray(moreDetailedMipLevel.Data, previousLevelX, previousLevelY, previousWidth);
var c10 = ByteRgba.FromByteArray(moreDetailedMipLevel.Data, ClampToDimension(previousLevelX + 1, previousWidth), previousLevelY, previousWidth);
var c01 = ByteRgba.FromByteArray(moreDetailedMipLevel.Data, previousLevelX, ClampToDimension(previousLevelY + 1, previousHeight), previousWidth);
var c11 = ByteRgba.FromByteArray(moreDetailedMipLevel.Data, ClampToDimension(previousLevelX + 1, previousWidth), ClampToDimension(previousLevelY + 1, previousHeight), previousWidth);
var interpolatedColor = ByteRgba.Average(c00, c10, c01, c11);
interpolatedColor.CopyTo(levelData, x, y, width);
}
}
mipMapData[level] = new TextureMipMapData
{
Data = levelData,
BytesPerRow = width * ByteRgba.BytesPerPixel
};
}
else
{
mipMapData[level] = new TextureMipMapData
{
Data = rgbaData,
BytesPerRow = width * ByteRgba.BytesPerPixel
};
}
previousWidth = width;
previousHeight = height;
width = Math.Max((int)Math.Floor(width / 2.0), 1);
height = Math.Max((int)Math.Floor(height / 2.0), 1);
}
return(mipMapData);
}
public static ByteRgba Average(ByteRgba v0, ByteRgba v1, ByteRgba v2, ByteRgba v3)
{
return(new ByteRgba
{
R = (byte)((v0.R + v1.R + v2.R + v3.R) / 4),
G = (byte)((v0.G + v1.G + v2.G + v3.G) / 4),
B = (byte)((v0.B + v1.B + v2.B + v3.B) / 4),
A = (byte)((v0.A + v1.A + v2.A + v3.A) / 4)
});
}
