Support writing SIGNED_RATIONAL tag types

Author: radarhere

Tests/test_file_libtiff.py

@@ -355,12 +355,15 @@ def test_subifd(self, tmp_path: Path) -> None:
             # Should not segfault
             im.save(outfile)
 
-    def test_ifd(self, monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> None:
+    @pytest.mark.parametrize("tagtype", (TiffTags.SIGNED_RATIONAL, TiffTags.IFD))
+    def test_tag_type(
+        self, tagtype: int, monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+    ) -> None:
         monkeypatch.setattr(TiffImagePlugin, "WRITE_LIBTIFF", True)
 
         ifd = TiffImagePlugin.ImageFileDirectory_v2()
         ifd[37000] = 100
-        ifd.tagtype[37000] = TiffTags.IFD
+        ifd.tagtype[37000] = tagtype
 
         out = tmp_path / "temp.tif"
         im = Image.new("L", (1, 1))

src/encode.c

@@ -990,10 +990,6 @@ PyImaging_LibTiffEncoderNew(PyObject *self, PyObject *args) {
                 status = ImagingLibTiffSetField(
                     &encoder->state, (ttag_t)key_int, (FLOAT32)PyFloat_AsDouble(value)
                 );
-            } else if (type == TIFF_DOUBLE) {
-                status = ImagingLibTiffSetField(
-                    &encoder->state, (ttag_t)key_int, (FLOAT64)PyFloat_AsDouble(value)
-                );
             } else if (type == TIFF_SBYTE) {
                 status = ImagingLibTiffSetField(
                     &encoder->state, (ttag_t)key_int, (INT8)PyLong_AsLong(value)
@@ -1002,7 +998,8 @@ PyImaging_LibTiffEncoderNew(PyObject *self, PyObject *args) {
                 status = ImagingLibTiffSetField(
                     &encoder->state, (ttag_t)key_int, PyBytes_AsString(value)
                 );
-            } else if (type == TIFF_RATIONAL) {
+            } else if (type == TIFF_DOUBLE || type == TIFF_SRATIONAL ||
+                       type == TIFF_RATIONAL) {
                 status = ImagingLibTiffSetField(
                     &encoder->state, (ttag_t)key_int, (FLOAT64)PyFloat_AsDouble(value)
                 );