To solve the issue of reading EXIF copyright data using the C-API, I added a simple function in libraw_c_api.c:

  DllDef int libraw_datastream_read(void *ifp, void *ptr, size_t size, size_t nmemb)
  {
    if (!ifp)
      return -1;
    return ((LibRaw_abstract_datastream *)ifp)->read(ptr, size, nmemb);
  }

Then from my application I can call that function from the exifparser callback installed using libraw_set_exifparser_handler.

Simple and easy.
Of course other similar functions may be added to call various LibRaw_abstract_datastream methods .

I wrote the code to install the callback and the callback gets called when a RAW file is read. Now, from the callback, when the wanted tag is seen, how to I call the datastream read method to read the tag value. The call back receive a pointer to LibRaw_abstract_datastream input stream. The question is how the datastream read method is called from the callback code which is [equivalent to] C code and as such has to use LibRaw C-API. I don't see anything in LibRaw C-API to use a datastream.

That is not a question related to Delphi but related to LibRaw C-API.
The question is: Using LibRaw C-API, how to call the datastream reader to read an EXIF tag value from the exif parser callback.

I have setup an exif parser callback. I correctly receive the copyright tag. I assume I have to read his value using passed ifp argument (The pointer to LibRaw_abstract_datastream input stream, positioned to start of data). But how can I do that using the C API?

Context: My program is written with Delphi which can use any C-API from DLL, but Delphi can't use C++ objects.

Thanks. I will try using EXIF callback. I come here again if I can't make it work.
Regards

Exif tag 0x8298 is not parsed by LibRaw

Thanks.

:Jack

return this->operator[](_fpos - _bstart);

We are happy to accept additions if they do not violate the general ideology of the library and solve a problem of interest to more than one user.
Please use github pull requests for such a contributions.

Delphi/other language wrappers are out of our interest because we'll unable to support such improvements.

> LibRaw should....

LibRaw is open-source, we welcome contributions from other developers

Yes, ppm_tiff_writer is a sample code only to allow LibRaw samples to write output files.

You may re-implement it, or use dcraw_mem_image() to create in-memory bitmap and save it using your own code.

Thank you.