Function decodeBlockATC

3rdparty/bimg/src/image.cpp:2553–2610

ATC

	// ATC
	//
	static void decodeBlockATC(uint8_t _dst[16*4], const uint8_t _src[8])
	{
		if (!BX_ENABLED(BIMG_DECODE_ATC) )
		{
			return;
		}

		uint8_t colors[4*4];

		uint32_t c0 = _src[0] | (_src[1] << 8);
		uint32_t c1 = _src[2] | (_src[3] << 8);

		if (0 == (c0 & 0x8000) )
		{
			colors[ 0] = bitRangeConvert( (c0>> 0)&0x1f, 5, 8);
			colors[ 1] = bitRangeConvert( (c0>> 5)&0x1f, 5, 8);
			colors[ 2] = bitRangeConvert( (c0>>10)&0x1f, 5, 8);

			colors[12] = bitRangeConvert( (c1>> 0)&0x1f, 5, 8);
			colors[13] = bitRangeConvert( (c1>> 5)&0x3f, 6, 8);
			colors[14] = bitRangeConvert( (c1>>11)&0x1f, 5, 8);

			colors[ 4] = (2 * colors[0] + colors[12]) / 3;
			colors[ 5] = (2 * colors[1] + colors[13]) / 3;
			colors[ 6] = (2 * colors[2] + colors[14]) / 3;

			colors[ 8] = (colors[0] + 2 * colors[12]) / 3;
			colors[ 9] = (colors[1] + 2 * colors[13]) / 3;
			colors[10] = (colors[2] + 2 * colors[14]) / 3;
		}
		else
		{
			colors[ 0] = 0;
			colors[ 1] = 0;
			colors[ 2] = 0;

			colors[ 8] = bitRangeConvert( (c0>> 0)&0x1f, 5, 8);
			colors[ 9] = bitRangeConvert( (c0>> 5)&0x1f, 5, 8);
			colors[10] = bitRangeConvert( (c0>>10)&0x1f, 5, 8);

			colors[12] = bitRangeConvert( (c1>> 0)&0x1f, 5, 8);
			colors[13] = bitRangeConvert( (c1>> 5)&0x3f, 6, 8);
			colors[14] = bitRangeConvert( (c1>>11)&0x1f, 5, 8);

			colors[ 4] = colors[ 8] - colors[12] / 4;
			colors[ 5] = colors[ 9] - colors[13] / 4;
			colors[ 6] = colors[10] - colors[14] / 4;
		}

		for (uint32_t ii = 0, next = 8*4; ii < 16*4; ii += 4, next += 2)
		{
			int32_t idx = ( (_src[next>>3] >> (next & 7) ) & 3) * 4;
			_dst[ii+0] = colors[idx+0];
			_dst[ii+1] = colors[idx+1];
			_dst[ii+2] = colors[idx+2];
			_dst[ii+3] = colors[idx+3];
		}
	}