Function decodeBlockEtc2ModeT

3rdparty/bimg/src/image.cpp:2640–2697

	}

	static void decodeBlockEtc2ModeT(uint8_t _dst[16*4], const uint8_t _src[8])
	{
		uint8_t rgb[16];

		// 0       1       2       3       4       5       6       7
		// 7654321076543210765432107654321076543210765432107654321076543210
		// ...rr.rrggggbbbbrrrrggggbbbbDD.Dmmmmmmmmmmmmmmmmllllllllllllllll
		//    ^            ^           ^   ^               ^
		//    +-- c0       +-- c1      |   +-- msb         +-- lsb
		//                             +-- dist

		rgb[ 0] = ( (_src[0] >> 1) & 0xc)
			    |   (_src[0]       & 0x3)
			    ;
		rgb[ 1] = _src[1] >> 4;
		rgb[ 2] = _src[1] & 0xf;

		rgb[ 8] = _src[2] >> 4;
		rgb[ 9] = _src[2] & 0xf;
		rgb[10] = _src[3] >> 4;

		rgb[ 0] = bitRangeConvert(rgb[ 0], 4, 8);
		rgb[ 1] = bitRangeConvert(rgb[ 1], 4, 8);
		rgb[ 2] = bitRangeConvert(rgb[ 2], 4, 8);
		rgb[ 8] = bitRangeConvert(rgb[ 8], 4, 8);
		rgb[ 9] = bitRangeConvert(rgb[ 9], 4, 8);
		rgb[10] = bitRangeConvert(rgb[10], 4, 8);

		uint8_t dist = ((_src[3] >> 1) & 0x6) | (_src[3] & 0x1);
		int32_t mod = s_etc2Mod[dist];

		rgb[ 4] = uint8_satadd(rgb[ 8],  mod);
		rgb[ 5] = uint8_satadd(rgb[ 9],  mod);
		rgb[ 6] = uint8_satadd(rgb[10],  mod);

		rgb[12] = uint8_satadd(rgb[ 8], -mod);
		rgb[13] = uint8_satadd(rgb[ 9], -mod);
		rgb[14] = uint8_satadd(rgb[10], -mod);

		uint32_t indexMsb = (_src[4]<<8) | _src[5];
		uint32_t indexLsb = (_src[6]<<8) | _src[7];

		for (uint32_t ii = 0; ii < 16; ++ii)
		{
			const uint32_t idx  = (ii&0xc) | ( (ii & 0x3)<<4);
			const uint32_t lsbi = indexLsb & 1;
			const uint32_t msbi = (indexMsb & 1)<<1;
			const uint32_t pal  = (lsbi | msbi)<<2;

			_dst[idx + 0] = rgb[pal+2];
			_dst[idx + 1] = rgb[pal+1];
			_dst[idx + 2] = rgb[pal+0];
			_dst[idx + 3] = 255;

			indexLsb >>= 1;
			indexMsb >>= 1;
		}
	}