add dcm_filehandle_find_frame_number()

[jcupitt]

• deprecate dcm_filehandle_get_frame_number()
• bump version to 1.3

See #117 for context

[jcupitt]

@bgilbert I tinkered a little and thought this was maybe the best way to fix it.

This PR adds:

bool dcm_filehandle_find_frame_number(DcmError **error,
                                      DcmFilehandle *filehandle,
                                      uint32_t column,
                                      uint32_t row,
                                      uint32_t *frame_number)

This new function only returns false on a parse error; if you have a missing tile, it sets frame_number to 0. DICOM frames number from 1, so this should be an unused value. It deprecates dcm_filehandle_get_frame_number().

With this obvious change to openslide:

        for (file_num = 0; file_num < l->file_count; file_num++) {
          DcmError *dcm_error = NULL;
          uint32_t n;
          if (!dcm_filehandle_find_frame_number(&dcm_error,
                                                l->files[file_num]->filehandle,
                                                tile_col, tile_row, &n)) {
            _openslide_dicom_propagate_error(err, dcm_error);
            return false;
          }
              
          if (n != 0) {
            // found one, record the file that has this tile and break
            l->tile_files[tile_index] = file_num;
            break; 
          } 
        }

Before this change, with the 6gb tiled full, no offset DICOM I have:

$ time slidetool slide open 4_1

real	0m1.861s
user	0m1.845s
sys	0m0.016s

With this PR and openslide change:

$ time slidetool slide open 4_1

real	0m0.328s
user	0m0.311s
sys	0m0.017s

Blimey!

[jcupitt]

The speed improvement is so useful I would be tempted to make the next openslide release require libdicom 1.3 with this change. It'd save an ugly #ifdef in openslide too.

What do you think?

[bgilbert]

The approach LGTM! Thanks for handling this. I agree with bumping the OpenSlide requirement directly to 1.3.0, since we haven't yet had a release that requires 1.2.0.

[jcupitt]

I think I fixed the things you saw, thanks for the careful review.

[bgilbert]

LGTM except for two small things.

[bgilbert]

LGTM, thanks for putting this together so quickly!