private void Decode_COMPRESSED_DXT1()
{
var colors = new OutputPixel[4];
for (int y = 0, ni = 0; y < _height; y += 4)
{
for (int x = 0; x < _width; x += 4, ni++)
{
var block = ((Dxt1Block *)_inputByte)[ni];
colors[0] = Decode_RGBA_5650_Pixel(block.Color0)
.Transform((r, g, b, a) => OutputPixel.FromRgba(b, g, r, a));
colors[1] = Decode_RGBA_5650_Pixel(block.Color1)
.Transform((r, g, b, a) => OutputPixel.FromRgba(b, g, r, a));
if (block.Color0 > block.Color1)
{
colors[2] = OutputPixel.OperationPerComponent(colors[0], colors[1],
(a, b) => (byte)(a * 2 / 3 + b * 1 / 3));
colors[3] = OutputPixel.OperationPerComponent(colors[0], colors[1],
(a, b) => (byte)(a * 1 / 3 + b * 2 / 3));
}
else
{
colors[2] = OutputPixel.OperationPerComponent(colors[0], colors[1],
(a, b) => (byte)(a * 1 / 2 + b * 1 / 2));
colors[3] = OutputPixel.FromRgba(0, 0, 0, 0);
}
var no = 0;
for (var y2 = 0; y2 < 4; y2++)
{
for (var x2 = 0; x2 < 4; x2++, no++)
{
var color = (block.ColorLookup >> (2 * no)) & 0x3;
var rx = x + x2;
var ry = y + y2;
var n = ry * _width + rx;
_output[n] = colors[color];
}
}
}
}
}
/// <summary>
/// DXT2 and DXT3 (collectively also known as Block Compression 2 or BC2) converts 16 input pixels
/// (corresponding to a 4x4 pixel block) into 128 bits of output, consisting of 64 bits of alpha channel data
/// (4 bits for each pixel) followed by 64 bits of color data, encoded the same way as DXT1 (with the exception
/// that the 4 color version of the DXT1 algorithm is always used instead of deciding which version to use based
/// on the relative values of and ). In DXT2, the color data is interpreted as being premultiplied by alpha, in
/// DXT3 it is interpreted as not having been premultiplied by alpha. Typically DXT2/3 are well suited to images
/// with sharp alpha transitions, between translucent and opaque areas.
/// </summary>
private void Decode_COMPRESSED_DXT3()
{
var colors = new OutputPixel[4];
var ni = 0;
for (var y = 0; y < _height; y += 4)
{
for (var x = 0; x < _width; x += 4, ni++)
{
var block = ((Dxt3Block *)_inputByte)[ni];
colors[0] = Decode_RGBA_5650_Pixel(block.Color0)
.Transform((r, g, b, a) => OutputPixel.FromRgba(b, g, r, a));
colors[1] = Decode_RGBA_5650_Pixel(block.Color1)
.Transform((r, g, b, a) => OutputPixel.FromRgba(b, g, r, a));
colors[2] = OutputPixel.OperationPerComponent(colors[0], colors[1],
(a, b) => (byte)(((a * 2) / 3) + ((b * 1) / 3)));
colors[3] = OutputPixel.OperationPerComponent(colors[0], colors[1],
(a, b) => (byte)(((a * 1) / 3) + ((b * 2) / 3)));
var no = 0;
for (var y2 = 0; y2 < 4; y2++)
{
for (var x2 = 0; x2 < 4; x2++, no++)
{
var alpha = (block.Alpha >> (4 * no)) & 0xF;
var color = (block.ColorLookup >> (2 * no)) & 0x3;
var rx = (x + x2);
var ry = (y + y2);
var n = ry * _width + rx;
_output[n] = colors[color];
_output[n].A = (byte)((alpha * 0xFF) / 0xF);
}
}
}
}
}
private void Decode_COMPRESSED_DXT5()
{
//Console.Error.WriteLine("Not Implemented: Decode_COMPRESSED_DXT5");
//throw new NotImplementedException();
//_Decode_Unimplemented();
var colors = new OutputPixel[4];
var ni = 0;
for (var y = 0; y < _height; y += 4)
{
for (var x = 0; x < _width; x += 4, ni++)
{
var block = ((Dxt5Block *)_inputByte)[ni];
colors[0] = Decode_RGBA_5650_Pixel(block.Color0)
.Transform((r, g, b, a) => OutputPixel.FromRgba(b, g, r, a));
colors[1] = Decode_RGBA_5650_Pixel(block.Color1)
.Transform((r, g, b, a) => OutputPixel.FromRgba(b, g, r, a));
colors[2] = OutputPixel.OperationPerComponent(colors[0], colors[1],
(a, b) => (byte)(a * 2 / 3 + b * 1 / 3));
colors[3] = OutputPixel.OperationPerComponent(colors[0], colors[1],
(a, b) => (byte)(a * 1 / 3 + b * 2 / 3));
// Create Alpha Lookup
var alphaLookup = new byte[8];
var alphas = (ushort)(block.Alpha >> 48);
var alpha0 = (byte)((alphas >> 0) & 0xFF);
var alpha1 = (byte)((alphas >> 8) & 0xFF);
alphaLookup[0] = alpha0;
alphaLookup[1] = alpha1;
if (alpha0 > alpha1)
{
alphaLookup[2] = (byte)((6 * alpha0 + alpha1) / 7);
alphaLookup[3] = (byte)((5 * alpha0 + 2 * alpha1) / 7);
alphaLookup[4] = (byte)((4 * alpha0 + 3 * alpha1) / 7);
alphaLookup[5] = (byte)((3 * alpha0 + 4 * alpha1) / 7);
alphaLookup[6] = (byte)((2 * alpha0 + 5 * alpha1) / 7);
alphaLookup[7] = (byte)((alpha0 + 6 * alpha1) / 7);
}
else
{
alphaLookup[2] = (byte)((4 * alpha0 + alpha1) / 5);
alphaLookup[3] = (byte)((3 * alpha0 + 2 * alpha1) / 5);
alphaLookup[4] = (byte)((2 * alpha0 + 3 * alpha1) / 5);
alphaLookup[5] = (byte)((alpha0 + 4 * alpha1) / 5);
alphaLookup[6] = (byte)0x00;
alphaLookup[7] = (byte)0xFF;
}
var no = 0;
for (var y2 = 0; y2 < 4; y2++)
{
for (var x2 = 0; x2 < 4; x2++, no++)
{
var alpha = alphaLookup[(block.Alpha >> (3 * no)) & 0x7];
var color = (block.ColorLookup >> (2 * no)) & 0x3;
var rx = x + x2;
var ry = y + y2;
var n = ry * _width + rx;
_output[n] = colors[color];
_output[n].A = alpha;
}
}
}
}
}