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python: cross the binding with exact bfloat16 / float8 dtypes

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Signed-off-by: Abhishek Gola <abhishek.gola@bigvisionllc.com>
This commit is contained in:
Abhishek Gola
2026-10-08 14:29:16 +05:30
parent 3b3a414c9c
commit 252b03de39
4 changed files with 144 additions and 9 deletions
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33
modules/python/src2/cv2_convert.cpp
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@@ -151,6 +151,8 @@ bool pyopencv_to(PyObject* o, Mat& m, const ArgInfo& info)
bool needcopy = false, needcast = false;
int typenum = PyArray_TYPE(oarr), new_typenum = typenum;
int type = numpyTypeToCvDepth(typenum);
if( type < 0 )
type = mlDtypeToCvDepth(typenum); // bfloat16 / float8, when ml_dtypes is installed
if( type < 0 )
{
@@ -332,12 +334,41 @@ bool pyopencv_to(PyObject* o, Mat& m, const ArgInfo& info)
return true;
}
// Hands a bfloat16 / float8 Mat back with its exact dtype; `descr` is the caller's to check.
static PyObject* pyopencv_from_mldtype(const cv::Mat& m, PyArray_Descr* descr)
{
cv::Mat cont;
if( m.isContinuous() )
cont = m;
else
ERRWRAP2(cont = m.clone());
const int cn = cont.channels();
int dims = cont.dims;
cv::AutoBuffer<npy_intp> _sizes(dims + 1);
for( int i = 0; i < dims; i++ )
_sizes[i] = (npy_intp)cont.size[i];
if( cn > 1 )
_sizes[dims++] = cn;
Py_INCREF(descr); // PyArray_NewFromDescr steals the reference
PyObject* o = PyArray_NewFromDescr(&PyArray_Type, descr, dims, _sizes.data(),
nullptr, nullptr, 0, nullptr);
if( !o )
return nullptr;
if( !cont.empty() )
memcpy(PyArray_DATA((PyArrayObject*)o), cont.data, cont.total() * cont.elemSize());
return o;
}
template<>
PyObject* pyopencv_from(const cv::Mat& m)
{
// NumPy has no bfloat16 or float8 dtype: widen these to float32 (lossless).
if( m.depth() == CV_16BF || m.depth() == CV_8F_E4M3FN || m.depth() == CV_8F_E4M3FNUZ )
{
if( PyArray_Descr* descr = mlDtypeDescrForCvDepth(m.depth()) )
return pyopencv_from_mldtype(m, descr);
// Without ml_dtypes NumPy cannot name these; widen to float32 (lossless).
cv::Mat m32f;
ERRWRAP2(m.convertTo(m32f, CV_32F));
return pyopencv_from(m32f);