Method transcode_image_level

engine/dlib/src/basis/transcoder/basisu_transcoder.cpp:10685–10834

	}

	bool basisu_transcoder::transcode_image_level(
		const void* pData, uint32_t data_size,
		uint32_t image_index, uint32_t level_index,
		void* pOutput_blocks, uint32_t output_blocks_buf_size_in_blocks_or_pixels,
		transcoder_texture_format fmt,
		uint32_t decode_flags, uint32_t output_row_pitch_in_blocks_or_pixels, basisu_transcoder_state *pState, uint32_t output_rows_in_pixels) const
	{
		const uint32_t bytes_per_block_or_pixel = basis_get_bytes_per_block_or_pixel(fmt);

		if (!m_ready_to_transcode)
		{
			BASISU_DEVEL_ERROR("basisu_transcoder::transcode_image_level: must call start_transcoding() first\n");
			return false;
		}

		//const bool transcode_alpha_data_to_opaque_formats = (decode_flags & cDecodeFlagsTranscodeAlphaDataToOpaqueFormats) != 0;

		if (decode_flags & cDecodeFlagsPVRTCDecodeToNextPow2)
		{
			BASISU_DEVEL_ERROR("basisu_transcoder::transcode_image_level: cDecodeFlagsPVRTCDecodeToNextPow2 currently unsupported\n");
			// TODO: Not yet supported
			return false;
		}

		if (!validate_header_quick(pData, data_size))
		{
			BASISU_DEVEL_ERROR("basisu_transcoder::transcode_image_level: header validation failed\n");
			return false;
		}

		const basis_file_header* pHeader = reinterpret_cast<const basis_file_header*>(pData);

		const uint8_t* pDataU8 = static_cast<const uint8_t*>(pData);

		const basis_slice_desc* pSlice_descs = reinterpret_cast<const basis_slice_desc*>(pDataU8 + pHeader->m_slice_desc_file_ofs);

		const bool basis_file_has_alpha_slices = (pHeader->m_flags & cBASISHeaderFlagHasAlphaSlices) != 0;

		int slice_index = find_first_slice_index(pData, data_size, image_index, level_index);
		if (slice_index < 0)
		{
			BASISU_DEVEL_ERROR("basisu_transcoder::transcode_image_level: failed finding slice index\n");
			// Unable to find the requested image/level 
			return false;
		}

		if ((fmt == transcoder_texture_format::cTFPVRTC1_4_RGBA) && (!basis_file_has_alpha_slices))
		{
			// Switch to PVRTC1 RGB if the input doesn't have alpha.
			fmt = transcoder_texture_format::cTFPVRTC1_4_RGB;
		}
				
		if (pHeader->m_tex_format == (int)basis_tex_format::cETC1S)
		{
			if (pSlice_descs[slice_index].m_flags & cSliceDescFlagsHasAlpha)
			{
				BASISU_DEVEL_ERROR("basisu_transcoder::transcode_image_level: alpha basis file has out of order alpha slice\n");