Allow uncompressed TIFF images to be saved in chunks

Tests/test_file_tiff.py

@@ -484,13 +484,13 @@ def test_modify_exif(self, tmp_path):
         outfile = str(tmp_path / "temp.tif")
         with Image.open("Tests/images/ifd_tag_type.tiff") as im:
             exif = im.getexif()
-            exif[256] = 100
+            exif[264] = 100
 
             im.save(outfile, exif=exif)
 
         with Image.open(outfile) as im:
             exif = im.getexif()
-            assert exif[256] == 100
+            assert exif[264] == 100
 
     def test_reload_exif_after_seek(self):
         with Image.open("Tests/images/multipage.tiff") as im:
@@ -781,6 +781,27 @@ def test_get_photoshop_blocks(self):
                 4001,
             ]
 
+    def test_tiff_chunks(self, tmp_path):
+        tmpfile = str(tmp_path / "temp.tif")
+
+        im = hopper()
+        with open(tmpfile, "wb") as fp:
+            for y in range(0, 128, 32):
+                chunk = im.crop((0, y, 128, y + 32))
+                if y == 0:
+                    chunk.save(
+                        fp,
+                        "TIFF",
+                        tiffinfo={
+                            TiffImagePlugin.IMAGEWIDTH: 128,
+                            TiffImagePlugin.IMAGELENGTH: 128,
+                        },
+                    )
+                else:
+                    fp.write(chunk.tobytes())
+
+        assert_image_equal_tofile(im, tmpfile)
+
     def test_close_on_load_exclusive(self, tmp_path):
         # similar to test_fd_leak, but runs on unixlike os
         tmpfile = str(tmp_path / "temp.tif")

Tests/test_file_tiff_metadata.py

@@ -164,6 +164,7 @@ def test_change_stripbytecounts_tag_type(tmp_path):
 
         # Resize the image so that STRIPBYTECOUNTS will be larger than a SHORT
         im = im.resize((500, 500))
+        info[TiffImagePlugin.IMAGEWIDTH] = im.width
 
         # STRIPBYTECOUNTS can be a SHORT or a LONG
         info.tagtype[TiffImagePlugin.STRIPBYTECOUNTS] = TiffTags.SHORT

src/PIL/TiffImagePlugin.py

@@ -1704,28 +1704,27 @@ def _save(im, fp, filename):
             colormap += [0] * (256 - colors)
         ifd[COLORMAP] = colormap
     # data orientation
-    stride = len(bits) * ((im.size[0] * bits[0] + 7) // 8)
+    w, h = ifd[IMAGEWIDTH], ifd[IMAGELENGTH]
+    stride = len(bits) * ((w * bits[0] + 7) // 8)
     if ROWSPERSTRIP not in ifd:
         # aim for given strip size (64 KB by default) when using libtiff writer
         if libtiff:
             im_strip_size = encoderinfo.get("strip_size", STRIP_SIZE)
-            rows_per_strip = (
-                1 if stride == 0 else min(im_strip_size // stride, im.size[1])
-            )
+            rows_per_strip = 1 if stride == 0 else min(im_strip_size // stride, h)
             # JPEG encoder expects multiple of 8 rows
             if compression == "jpeg":
-                rows_per_strip = min(((rows_per_strip + 7) // 8) * 8, im.size[1])
+                rows_per_strip = min(((rows_per_strip + 7) // 8) * 8, h)
         else:
-            rows_per_strip = im.size[1]
+            rows_per_strip = h
         if rows_per_strip == 0:
             rows_per_strip = 1
         ifd[ROWSPERSTRIP] = rows_per_strip
     strip_byte_counts = 1 if stride == 0 else stride * ifd[ROWSPERSTRIP]
-    strips_per_image = (im.size[1] + ifd[ROWSPERSTRIP] - 1) // ifd[ROWSPERSTRIP]
+    strips_per_image = (h + ifd[ROWSPERSTRIP] - 1) // ifd[ROWSPERSTRIP]
     if strip_byte_counts >= 2**16:
         ifd.tagtype[STRIPBYTECOUNTS] = TiffTags.LONG
     ifd[STRIPBYTECOUNTS] = (strip_byte_counts,) * (strips_per_image - 1) + (
-        stride * im.size[1] - strip_byte_counts * (strips_per_image - 1),
+        stride * h - strip_byte_counts * (strips_per_image - 1),
     )
     ifd[STRIPOFFSETS] = tuple(
         range(0, strip_byte_counts * strips_per_image, strip_byte_counts)