It depends on the content of the texture.I think I did not give to understand.
Which format is recommended to save it?
Is it RGB or ARGB?
For RGB BC1 / DXT1
For ARGB Alpha Exponent (DXT 5)?
I do not know what CG software this is,
In case of DDS
RGB is DXT1 non alpha
ARGB 4 bpp is DXT 1 1 bit alpha (in the case of white or black clipping)
ARGB 8 bpp is DXT 5
We will take two representative colors first with 8 bit grayscale (256 gradations). For the number of intermediate colors to be generated after this, color parts make up two colors, alpha creates six colors. It is a total of 8 colors.
DXT 3 is not used in black desert