Function sam2_preprocess_image

sam3.cpp:3522–3548

SAM2 preprocessing: resize + ImageNet normalization. Returns [C, H, W] float, mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225].

// SAM2 preprocessing: resize + ImageNet normalization.
// Returns [C, H, W] float, mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225].
static std::vector<float> sam2_preprocess_image(const sam3_image& image, int img_size) {
    static const float mean[3] = {0.485f, 0.456f, 0.406f};
    static const float std_d[3] = {0.229f, 0.224f, 0.225f};
    const int C = 3;
    std::vector<float> result(C * img_size * img_size);

    std::vector<uint8_t> resized;
    const uint8_t* pixels = image.data.data();
    int w = image.width, h = image.height;

    if (w != img_size || h != img_size) {
        resized.resize(img_size * img_size * 3);
        sam3_resize_bilinear(pixels, w, h, resized.data(), img_size, img_size);
        pixels = resized.data();
    }

    for (int c = 0; c < C; ++c) {
        for (int y = 0; y < img_size; ++y) {
            for (int x = 0; x < img_size; ++x) {
                float v = pixels[(y * img_size + x) * 3 + c] / 255.0f;
                result[c * img_size * img_size + y * img_size + x] = (v - mean[c]) / std_d[c];
            }
        }
    }

    return result;
}

/*****************************************************************************
** RoPE — 2D axial rotary positional embeddings