protected void DecompressColors(
byte[] data, int startIndex,
bool use1BitAlphaTrick,
byte[] result,
int resultX, int resultY,
int resultStride)
{
var packedColor0 = (ushort)(data[startIndex + 0] | (data[startIndex + 1] << 8));
var packedColor1 = (ushort)(data[startIndex + 2] | (data[startIndex + 3] << 8));
var color0 = ColorRgba.UnpackRgbFromBgr565(packedColor0);
var color1 = ColorRgba.UnpackRgbFromBgr565(packedColor1);
ColorRgba color2, color3;
if (!use1BitAlphaTrick || packedColor0 > packedColor1)
{
color2 = (2.0 / 3.0) * color0 + (1.0 / 3.0) * color1;
color3 = (1.0 / 3.0) * color0 + (2.0 / 3.0) * color1;
}
else
{
color2 = 0.5 * color0 + 0.5 * color1;
color3 = ColorRgba.TransparentBlack;
}
var colors = new[]
{
color0,
color1,
color2,
color3
};
var y = resultY;
for (var i = 4; i < 8; i++)
{
var byteValue = data[startIndex + i];
// 4 x 2-bit index values in each byte.
var x = resultX;
for (var j = 0; j < 4; j++)
{
var indexValue = (byteValue >> (j * 2)) & 0b11;
var color = colors[indexValue];
result[(y * resultStride) + (x + 0)] = color.R;
result[(y * resultStride) + (x + 1)] = color.G;
result[(y * resultStride) + (x + 2)] = color.B;
if (use1BitAlphaTrick)
{
result[(y * resultStride) + (x + 3)] = color.A;
}
x += 4;
}
y++;
}
}
