Method preprocess_image

src/common/AutoModel/modeling_qwen3vl_image.cpp:161–245

@brief: preprocess the image for Qwen3VL model @note: Converts uint8 image to BF16 format, data is already in (3, H, W) CHW layout @param: image: the image to preprocess (already in CHW format) @return: the preprocessed image in BF16 format

///@param: image: the image to preprocess (already in CHW format)
///@return: the preprocessed image in BF16 format
void Qwen3VL::preprocess_image(qwen3vl_image_t& image, std::vector<bf16> &pixel_values) {
    const int width = image.width;
    const int height = image.height;
    const int channels = 3; // RGB
    int resized_height; 
    int resized_width;    
    // do the automatically resizing in here 
    smart_resize(
        height, width,
        resized_height, resized_width,
        QWEN3_PATCH_SIZE * QWEN3_IMAGE_MERGE_SIZE,
        QWEN3_SHORTEST_EDGE,
        QWEN3_LONGEST_EDGE
    );
    // std::cout << "resized_height "<< resized_height << " resized_width " << resized_width <<std::endl;

    // Cache size calculations for efficiency
    const uint32_t single_frame_size = resized_height * resized_width * channels;
    const uint32_t total_patch_size = single_frame_size * QWEN3_TEMPORAL_PATCH_SIZE;
    const uint32_t grid_h = resized_height / QWEN3_PATCH_SIZE;
    const uint32_t grid_w = resized_width / QWEN3_PATCH_SIZE;

    // Pre-allocate final buffer to avoid reallocation
    const uint32_t prev_pixel_values_size = pixel_values.size();
    pixel_values.resize(prev_pixel_values_size + total_patch_size);

    // Use non-optimized path for consistent results across platforms
    auto resize_image =  imgproc::avx512::resize_bicubic_antialias_rgb_planar_avx512(
        image._data.data(), width, height, resized_width, resized_height, true
    );

    // Reuse scratch buffer across calls to avoid repeated allocations
    static thread_local std::vector<float> patch_vector_scratch;
    if (patch_vector_scratch.size() < total_patch_size) {
        patch_vector_scratch.resize(total_patch_size);
    }
    
    // Apply rescale and normalization to first frame
    imgproc::avx512::rescale_and_normalize_avx512(
        resize_image.data(), patch_vector_scratch.data(),
        resized_width, resized_height, channels,
        true, QWEN3_VISION_RESCALE_FACTOR,
        true, QWEN3_VISION_RESCALE_IMAGE_MEAN, QWEN3_VISION_RESCALE_IMAGE_STD
    );
    
    // Replicate first frame for temporal patches (optimized for QWEN3_TEMPORAL_PATCH_SIZE = 2)
    // This is more efficient than a loop for the common case
    if constexpr (QWEN3_TEMPORAL_PATCH_SIZE == 2) {
        memcpy(
            patch_vector_scratch.data() + single_frame_size,
            patch_vector_scratch.data(),
            single_frame_size * sizeof(float)
        );
    } else {
        // Generic loop for other TEMPORAL_PATCH_SIZE values
        for(unsigned l = 1; l < QWEN3_TEMPORAL_PATCH_SIZE; l++){
            memcpy(
                patch_vector_scratch.data() + l * single_frame_size,