Method get_image_info

external/basisu/transcoder/basisu_transcoder.cpp:9992–10055

	}

	bool basisu_transcoder::get_image_info(const void* pData, uint32_t data_size, basisu_image_info& image_info, uint32_t image_index) const
	{
		if (!validate_header_quick(pData, data_size))
		{
			BASISU_DEVEL_ERROR("basisu_transcoder::get_image_info: header validation failed\n");
			return false;
		}

		int slice_index = find_first_slice_index(pData, data_size, image_index, 0);
		if (slice_index < 0)
		{
			BASISU_DEVEL_ERROR("basisu_transcoder::get_image_info: invalid slice index\n");
			return false;
		}

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

		if (image_index >= pHeader->m_total_images)
		{
			BASISU_DEVEL_ERROR("basisu_transcoder::get_image_info: invalid image_index\n");
			return false;
		}

		const basis_slice_desc* pSlice_descs = reinterpret_cast<const basis_slice_desc*>(static_cast<const uint8_t*>(pData) + pHeader->m_slice_desc_file_ofs);

		uint32_t total_levels = 1;
		for (uint32_t i = slice_index + 1; i < pHeader->m_total_slices; i++)
			if (pSlice_descs[i].m_image_index == image_index)
				total_levels = basisu::maximum<uint32_t>(total_levels, pSlice_descs[i].m_level_index + 1);
			else
				break;

		if (total_levels > 16)
		{
			BASISU_DEVEL_ERROR("basisu_transcoder::get_image_info: invalid image_index\n");
			return false;
		}

		const basis_slice_desc& slice_desc = pSlice_descs[slice_index];

		image_info.m_image_index = image_index;
		image_info.m_total_levels = total_levels;
		
		image_info.m_alpha_flag = false;

		// For ETC1S, if anything has alpha all images have alpha. For UASTC, we only report alpha when the image actually has alpha.
		if (pHeader->m_tex_format == (int)basis_tex_format::cETC1S)
			image_info.m_alpha_flag = (pHeader->m_flags & cBASISHeaderFlagHasAlphaSlices) != 0; 
		else
			image_info.m_alpha_flag = (slice_desc.m_flags & cSliceDescFlagsHasAlpha) != 0;

		image_info.m_iframe_flag = (slice_desc.m_flags & cSliceDescFlagsFrameIsIFrame) != 0;

		image_info.m_width = slice_desc.m_num_blocks_x * 4;
		image_info.m_height = slice_desc.m_num_blocks_y * 4;
		image_info.m_orig_width = slice_desc.m_orig_width;
		image_info.m_orig_height = slice_desc.m_orig_height;
		image_info.m_num_blocks_x = slice_desc.m_num_blocks_x;