Function transcode_hdr

example/example.cpp:235–323

This example function loads a .KTX2 file and then transcodes it to various compressed/uncompressed texture formats. It writes .DDS and .ASTC files. ARM's astcenc tool can be used to unpack the .ASTC file: astcenc-avx2.exe -dh test_uastc_hdr_astc.astc out.exr

// ARM's astcenc tool can be used to unpack the .ASTC file: 
// astcenc-avx2.exe -dh test_uastc_hdr_astc.astc out.exr
static bool transcode_hdr()
{
    // Note: The encoder already initializes the transcoder, but if you haven't initialized the encoder you MUST call this function to initialize the transcoder.
    basist::basisu_transcoder_init();

    // Read the .KTX2 file's data into memory.
    uint8_vec ktx2_file_data;
    if (!read_file_to_vec("test_uastc_hdr.ktx2", ktx2_file_data))
        return false;

    // Create the KTX2 transcoder object.
    basist::ktx2_transcoder transcoder;

    // Initialize the transcoder.
    if (!transcoder.init(ktx2_file_data.data(), ktx2_file_data.size_u32()))
        return false;

    const uint32_t width = transcoder.get_width();
    const uint32_t height = transcoder.get_height();

    printf("Texture dimensions: %ux%u, levels: %u\n", width, height, transcoder.get_levels());

    // This example only transcodes UASTC HDR textures.
    if (!transcoder.is_hdr())
        return false;
        
    // Begin transcoding (this will be a no-op with UASTC HDR textures, but you still need to do it. For ETC1S it'll unpack the global codebooks.)
    transcoder.start_transcoding();
            
    // Transcode to BC6H and write a BC6H .DDS file.
    {
        gpu_image tex(texture_format::cBC6HUnsigned, width, height);

        bool status = transcoder.transcode_image_level(0, 0, 0,
            tex.get_ptr(), tex.get_total_blocks(),
            basist::transcoder_texture_format::cTFBC6H, 0);
        if (!status)
            return false;

        gpu_image_vec tex_vec;
        tex_vec.push_back(tex);
        if (!write_compressed_texture_file("test_uastc_hdr_bc6h.dds", tex_vec, false))
            return false;
    }

    // Transcode to ASTC HDR 4x4 and write a ASTC 4x4 HDR .astc file.
    {
        gpu_image tex(texture_format::cASTC_HDR_4x4, width, height);

        bool status = transcoder.transcode_image_level(0, 0, 0,
            tex.get_ptr(), tex.get_total_blocks(),
            basist::transcoder_texture_format::cTFASTC_HDR_4x4_RGBA, 0);
        if (!status)
            return false;

        if (!write_astc_file("test_uastc_hdr_astc.astc", tex.get_ptr(), 4, 4, tex.get_pixel_width(), tex.get_pixel_height()))
            return false;
    }