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1.

CC_MIXED ( similar to other S3TC ): A 4x4 texel block is represented by two bits-per-texel for opaque textures.

Additionally, each block has two 16-bit colors stored in an RGB 565 format.

The two RGB 565 colors and two additional colors ( created by interpolating between the two RGB 565 colors ) form the primary colors for this texel block and its associated four color lookup table.

A 2-bit index is used to determine which color from the lookup table will be used for each texel in the 4x4 block.

Transparent textures are created by making one of the four colors transparent.