Fix setting of TIFF ExtraSamples tag.

- force cast ExtraSamples to a list.
- fix calls to ImagingLibTiffSetField to include array length.

PIL/TiffImagePlugin.py

@@ -1183,6 +1183,8 @@ def _save(im, fp, filename):
         atts = {}
         # bits per sample is a single short in the tiff directory, not a list.
         atts[BITSPERSAMPLE] = bits[0]
+        if EXTRASAMPLES in ifd:
+            atts[EXTRASAMPLES] = list(ifd[EXTRASAMPLES])
         # Merge the ones that we have with (optional) more bits from
         # the original file, e.g x,y resolution so that we can
         # save(load('')) == original file.

encode.c

@@ -770,7 +770,7 @@ PyImaging_LibTiffEncoderNew(PyObject* self, PyObject* args)
                         }
                         status = ImagingLibTiffSetField(&encoder->state,
                                                         (ttag_t) PyInt_AsLong(key),
-                                                        intav);
+                                                        len, intav);
                         free(intav);
                     }
                 } else {
@@ -782,7 +782,7 @@ PyImaging_LibTiffEncoderNew(PyObject* self, PyObject* args)
                         }
                         status = ImagingLibTiffSetField(&encoder->state,
                                                         (ttag_t) PyInt_AsLong(key),
-                                                        floatav);
+                                                        len, floatav);
                         free(floatav);
                     }
                 }