private static byte[] ReadColor(int pixelDepth, BinaryReader reader)
{
switch (pixelDepth)
{
case 16:
{
var color16 = reader.ReadInt16();
return(Tga.FlipRgb(
new[]
{
(byte)(((color16 >> 0) & 0x1f) * 0xff / 0x1f), (byte)(((color16 >> 5) & 0x1f) * 0xff / 0x1f),
(byte)(((color16 >> 10) & 0x1f) * 0xff / 0x1f),
// It seems the alpha value is not used here...
//(byte) ((color16 >> 15) * 0xff)
(byte)0xff
}
));
}
case 24:
return(Tga.FlipRgb(new[] { reader.ReadByte(), reader.ReadByte(), reader.ReadByte(), (byte)0xff }));
case 32:
return(Tga.FlipRgb(new[] { reader.ReadByte(), reader.ReadByte(), reader.ReadByte(), reader.ReadByte() }));
default:
return(new byte[4]);
}
}
public Tga(Stream stream)
{
using var reader = new BinaryReader(stream);
if (reader.ReadByte() != 0x00)
{
throw new Exception("Unsupported IDLength");
}
var colorMapType = reader.ReadByte();
if (colorMapType != 0x00 && colorMapType != 0x01)
{
throw new Exception("Unsupported ColorMapType");
}
var imageType = reader.ReadByte();
if (imageType != 0x00 && imageType != 0x01 && imageType != 0x02 && imageType != 0x0a)
{
throw new Exception("Unsupported ImageType");
}
var firstIndexEntry = 0;
var colorMapLength = 0;
var colorMapEntrySize = 0;
// This is a custom tga format, as this imageType means originally "no image".
if (imageType == 0x00)
{
reader.ReadBytes(3);
}
else
{
firstIndexEntry = reader.ReadUInt16();
colorMapLength = reader.ReadUInt16();
colorMapEntrySize = reader.ReadByte();
if (colorMapType == 0x01)
{
if (firstIndexEntry + colorMapLength > 256 || colorMapLength == 0)
{
throw new Exception("Unsupported ColorMap");
}
if (colorMapEntrySize != 16 && colorMapEntrySize != 24 && colorMapEntrySize != 32)
{
throw new Exception("Unsupported ColorMap");
}
}
else if (firstIndexEntry != 0 || colorMapLength != 0 || colorMapEntrySize != 0)
{
throw new Exception("Unsupported ColorMap");
}
if (reader.ReadUInt16() != 0x0000)
{
throw new Exception("Unsupported XOrigin");
}
if (reader.ReadUInt16() != 0x0000)
{
throw new Exception("Unsupported YOrigin");
}
}
this.Width = reader.ReadUInt16();
this.Height = reader.ReadUInt16();
var pixelDepth = reader.ReadByte();
if (colorMapType == 0x01)
{
if (pixelDepth != 8)
{
throw new Exception("Unsupported PixelDepth");
}
}
else if (pixelDepth != 16 && pixelDepth != 24 && pixelDepth != 32)
{
throw new Exception("Unsupported PixelDepth");
}
// TODO implement alphaBits
var alphaBits = 0;
var flipHorizontal = false;
var flipVertical = false;
if (imageType != 0x00)
{
var imageDescriptor = reader.ReadByte();
alphaBits = imageDescriptor & 0x0f;
flipHorizontal = (imageDescriptor & 0x10) != 0x00;
flipVertical = (imageDescriptor & 0x20) != 0x00;
if (imageDescriptor >> 6 != 0x00)
{
throw new Exception("Unsupported ImageDescriptor");
}
// TODO what does it mean when alphaBits are 8?
if (pixelDepth == 8 && alphaBits != 0 && alphaBits != 8)
{
throw new Exception("Unsupported AlphaBits");
}
// TODO what does it mean when alphaBits are 0?
if (pixelDepth == 16 && alphaBits != 1 && alphaBits != 0)
{
throw new Exception("Unsupported AlphaBits");
}
if (pixelDepth == 24 && alphaBits != 0)
{
throw new Exception("Unsupported AlphaBits");
}
// TODO what does it mean when alphaBits are 0?
if (pixelDepth == 32 && alphaBits != 8 && alphaBits != 0)
{
throw new Exception("Unsupported AlphaBits");
}
}
this.Pixels = new byte[this.Width * this.Height * 4];
var colorMap = new byte[colorMapLength * 4];
if (colorMapType == 0x01)
{
for (var i = 0; i < colorMapLength; i++)
{
Array.Copy(Tga.ReadColor(colorMapEntrySize, reader), 0, colorMap, i * 4, 4);
}
}
var pixelReader = reader;
if (imageType == 0x0a)
{
var bytesPerPixel = pixelDepth / 8;
var uncompressed = new byte[this.Width * this.Height * bytesPerPixel];
for (var i = 0; i < uncompressed.Length;)
{
var info = reader.ReadByte();
var mode = info >> 7;
var count = (info & 0x7f) + 1;
if (mode == 1)
{
var pixel = Tga.ReadColor(pixelDepth, reader);
for (var j = 0; j < count; j++, i += bytesPerPixel)
{
Array.Copy(pixel, 0, uncompressed, i, bytesPerPixel);
}
}
else
{
var numBytes = bytesPerPixel * count;
Array.Copy(reader.ReadBytes(numBytes), 0, uncompressed, i, numBytes);
i += numBytes;
}
}
pixelReader = new BinaryReader(new MemoryStream(uncompressed));
}
for (var y = 0; y < this.Height; y++)
{
for (var x = 0; x < this.Width; x++)
{
var rgba = new byte[4];
if (colorMapType == 0x01)
{
Array.Copy(colorMap, (pixelReader.ReadByte() - firstIndexEntry) * 4, rgba, 0, 4);
}
else
{
rgba = Tga.ReadColor(pixelDepth, pixelReader);
}
if (rgba[0] == 0xff && rgba[1] == 0x00 && rgba[2] == 0xff && rgba[3] == 0xff)
{
continue;
}
Array.Copy(rgba, 0, this.Pixels, ((flipVertical ? this.Height - 1 - y : y) * this.Width + (flipHorizontal ? this.Width - 1 - x : x)) * 4, 4);
}
}
}