Allow passing None instead of np.array

[laggykiller]

I want to be able to pass None to trns_color.

I have read: https://nanobind.readthedocs.io/en/latest/porting.html and I have changed to "trns_color"_a.none(). I have also tried "trns_color"_a = nb::none()

NB_MODULE(MODULE_NAME, m) {
    m.doc() = "A nanobind API for apngasm, a tool/library for APNG assembly/disassembly";
    m.attr("__version__") = VERSION_INFO;

    m.def("create_frame_from_rgb", [](
        nb::ndarray<unsigned char, nb::shape<nb::any, nb::any, 3>> *pixels,
        unsigned int width, unsigned int height,
        nb::ndarray<unsigned char, nb::shape<3>> *trns_color,
        unsigned delayNum = apngasm::DEFAULT_FRAME_NUMERATOR,
        unsigned delayDen = apngasm::DEFAULT_FRAME_DENOMINATOR
    ) APNGASM_PY_DECLSPEC {
        apngasm::rgb *pixelsNew = new apngasm::rgb[pixels->shape(0)*pixels->shape(1)];
        unsigned char *pixels_ptr = pixels->data();

        for (int y = 0; y < pixels->shape(0); ++y) {
            for (int x = 0; x < pixels->shape(1); ++x) {
                pixelsNew[pixels->shape(1)*y + x].r = pixels_ptr[pixels->shape(2)*pixels->shape(1)*y + pixels->shape(2)*x];
                pixelsNew[pixels->shape(1)*y + x].g = pixels_ptr[pixels->shape(2)*pixels->shape(1)*y + pixels->shape(2)*x + 1];
                pixelsNew[pixels->shape(1)*y + x].b = pixels_ptr[pixels->shape(2)*pixels->shape(1)*y + pixels->shape(2)*x + 2];
            }
        }

        apngasm::rgb *trns_color_new = new apngasm::rgb;

        if (trns_color != NULL) {
            unsigned char *trns_color_ptr = trns_color->data();
            trns_color_new->r = trns_color_ptr[0];
            trns_color_new->g = trns_color_ptr[1];
            trns_color_new->b = trns_color_ptr[2];
        } else {
            trns_color_new = NULL;
        }

        const apngasm::APNGFrame frame(pixelsNew, width, height, trns_color_new, delayNum, delayDen);
        delete[] pixelsNew;
        delete trns_color_new;
        return frame;
    },
    "pixels"_a, "width"_a, "height"_a, "trns_color"_a.none(), "delay_num"_a = apngasm::DEFAULT_FRAME_NUMERATOR, "delay_den"_a = apngasm::DEFAULT_FRAME_DENOMINATOR,
    R"pbdoc(
    Creates an APNGFrame from a bitmapped array of RBG pixel data.
    
    :param numpy.typing.NDArray pixels: The RGB pixel data, expressed as 3D numpy array.
    :param int width: The width of the pixel data.
    :param int height: The height of the pixel data.
    :param Optional[numpy.typing.NDArray] trns_color: The color [r, g, b] to be treated as transparent, expressed as 1D numpy array.
    :param int delay_num: The delay numerator for this frame (defaults to DEFAULT_FRAME_NUMERATOR).
    :param int delay_den: The delay denominator for this frame (defaults to DEFAULT_FRAME_DENMINATOR).
    
    :return: A APNGFrame object.
    :rtype: apngasm_python._apngasm_python.APNGFrame
    )pbdoc");

However:

>>> from apngasm_python._apngasm_python import APNGAsm, APNGFrame, create_frame_from_rgb, create_frame_from_rgba
>>> import numpy as np
>>> frame = create_frame_from_rgb(pixels=np.array([[[0,0,0]]]), width=1, height=1, trns_color=np.array([0,0,0])) # No error
>>> frame = create_frame_from_rgb(pixels=np.array([[[0,0,0]]]), width=1, height=1, trns_color=None)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: create_frame_from_rgb(): incompatible function arguments. The following argument types are supported:
    1. create_frame_from_rgb(pixels: ndarray[dtype=uint8, shape=(*, *, 3)], width: int, height: int, trns_color: Optional[ndarray[dtype=uint8, shape=(3)]], delay_num: int = 100, delay_den: int = 1000) -> apngasm_python._apngasm_python.APNGFrame

Invoked with types: kwargs = { pixels: ndarray, width: int, height: int, trns_color: NoneType }

I have also tried to change the lambda function into a separate function, but still does not work.

Full code: https://github.com/laggykiller/apngasm-python/tree/3d-array

[laggykiller]

Nevermind, I figured it out. As mentioned in https://nanobind.readthedocs.io/en/latest/porting.html#none-null-arguments

None-valued arguments are only supported by two of the three parameter passing styles described in the section on information exchange. In particular, they are supported by bindings and wrappers, but not by type casters.

I am using type casters, so it did not work.