Handle detecting the need for big tiff in offsets.

CHANGELOG.md

@@ -1,7 +1,12 @@
 # Change Log
 
-## Unreleased
-- More tags
+## Version 1.2.1
+
+### Improvements
+- More tags (#42)
+
+### Bug fixes
+- Better detect the need to write bigtiff files (#43)
 
 ## Version 1.2.0
 

tests/test_write_tiff.py

@@ -75,6 +75,23 @@ def test_write_bigtiff_with_long_data(tmp_path):
     assert destinfo['bigtiff'] is True
 
 
+def test_write_bigtiff_with_offset_data(tmp_path):
+    path = datastore.fetch('hamamatsu.ndpi')
+    info = tifftools.read_tiff(path)
+    info['ifds'][0]['tags'][tifftools.Tag.FreeOffsets.value] = {
+        'datatype': tifftools.Datatype.LONG,
+        'data': [8] * 256,
+    }
+    info['ifds'][0]['tags'][tifftools.Tag.FreeByteCounts.value] = {
+        'datatype': tifftools.Datatype.LONG,
+        'data': [16777216] * 256,
+    }
+    destpath = tmp_path / 'sample.tiff'
+    tifftools.write_tiff(info, destpath)
+    destinfo = tifftools.read_tiff(destpath)
+    assert destinfo['bigtiff'] is True
+
+
 def test_write_bytecount_data(tmp_path):
     path = os.path.join(os.path.dirname(__file__), 'data', 'good_single.tif')
     info = tifftools.read_tiff(path)

tifftools/tifftools.py

@@ -341,6 +341,9 @@ def write_ifd(dest, bom, bigtiff, ifd, ifdPtr, tagSet=Tag):
                 else:
                     data = write_tag_data(
                         dest, src, data, [tag.bytecounts] * count, ifd['size'])
+                if not bigtiff and any(val for val in data if val >= 0x100000000):
+                    raise MustBeBigTiffException(
+                        'The file is large enough it must be in bigtiff format.')
                 taginfo = taginfo.copy()
                 taginfo['datatype'] = Datatype.LONG8 if bigtiff else Datatype.LONG
             if not bigtiff and Datatype[taginfo['datatype']] in {Datatype.LONG8, Datatype.SLONG8}: