Libtiff metadata writing fixes #2288

wiredfool · 2016-12-13T12:04:42Z

Fixes #1765, #1147, #1597 (among others, likely)

Libtiff's metadata support is tricky and dangerous. This patch is 1/3 of the work to clean up our support for it.

Understand and support writing basic metadata through libtiff. This includes casting numbers to the correct format and passing in arrays correctly for known items. (e.g., this fixes Save compressed TIFF only accepts float values for dpi #1765, writing ints to dpi, and writing the colormap for P mode images)
Consider supporting custom metadata tags safely. This is going to require reflection from libtiff to ensure that we're setting items correctly.
Coordinate this work with the python metadata implementation in two places: When reading images where the type conflicts with the spec, and when writing (in python) metadata of incorrect types.

While this is not finished, I believe that this is a material improvement in the support for tiff metadata, and can be merged (after I'm happy and rebased out some things) for 3.5.

…ach?

wiredfool · 2016-12-14T16:52:30Z

Last few commits are the start of 2 and 3, but there's an issue with the sampleformat due to the differences between how we've had it defined and in tiff files, and how it's in the api. Additionally, I think the failures on appveyor are due to a libtiff5 vs libtiff4 difference.

Upshot is, I think I've got to handle most of this to do it right, and doing just 1 isn't going to cut it.

radarhere · 2018-09-08T07:59:10Z

Note that PR #3338 added a fix for #1765, so this PR will have to consider that change, or maybe just revert it in favour of this work.

radarhere · 2020-05-25T23:07:02Z

encode.c

+                    int stride = 256;
+                    TRACE(("Setting ColorMap\n"));
+                  if (len != 768) {
+                        PyErr_SetString(PyExc_ValueError, "Requiring 768 items for for Colormap");


Suggested change

PyErr_SetString(PyExc_ValueError, "Requiring 768 items for for Colormap");

PyErr_SetString(PyExc_ValueError, "Requiring 768 items for Colormap");

radarhere · 2020-05-25T23:13:38Z

Tests/test_file_libtiff.py

+
+        reloaded = Image.open(out)
+        # colormap/palette tag
+        self.assertTrue(len(reloaded.tag_v2[320]), 768)


Suggested change

self.assertTrue(len(reloaded.tag_v2[320]), 768)

self.assertEqual(len(reloaded.tag_v2[320]), 768)

radarhere · 2021-08-01T13:46:02Z

PIL/TiffTags.py

-    280: ("MinSampleValue", LONG, 0),
-    281: ("MaxSampleValue", SHORT, 0),
+    280: ("MinSampleValue", LONG, 1),
+    281: ("MaxSampleValue", SHORT, 1),


I don't see why this change was made - https://www.awaresystems.be/imaging/tiff/tifftags/minsamplevalue.html and https://www.awaresystems.be/imaging/tiff/tifftags/maxsamplevalue.html

radarhere · 2022-08-02T09:04:52Z

docs/reference/tiff_metadata.rst

+Tiff Metadata
+=============
+
+Pillow currently reads TIFF metadata in pure python and writes either


Suggested change

Pillow currently reads TIFF metadata in pure python and writes either

Pillow currently reads TIFF metadata in pure Python and writes either

radarhere · 2025-07-26T11:18:49Z

PIL/TiffTags.py

    324: ("TileOffsets", LONG, 0),
    325: ("TileByteCounts", LONG, 0),

+    330: ("SubIFD", SHORT, 1),


#6569 added this tag, but as "SubIFDs", LONG and 0, which matches https://web.archive.org/web/20240329145255/https://www.awaresystems.be/imaging/tiff/tifftags/subifds.html

radarhere · 2025-07-26T11:24:42Z

PIL/TiffTags.py

-    340: ("SMinSampleValue", DOUBLE, 0),
-    341: ("SMaxSampleValue", DOUBLE, 0),
+    340: ("SMinSampleValue", DOUBLE, 1),
+    341: ("SMaxSampleValue", DOUBLE, 1),


I don't see why these changes were made -
https://web.archive.org/web/20240329145340/https://www.awaresystems.be/imaging/tiff/tifftags/sampleformat.html
https://web.archive.org/web/20240329145243/https://www.awaresystems.be/imaging/tiff/tifftags/sminsamplevalue.html
https://web.archive.org/web/20240329145243/https://www.awaresystems.be/imaging/tiff/tifftags/smaxsamplevalue.html

radarhere · 2025-10-12T05:02:51Z

PIL/TiffTags.py

+    32995:("Matteing", SHORT, 1),
+    32996:("DataType", SHORT, 1),
+    32997:("ImageDepth", LONG, 1),
+    32998:("TileDepth", LONG, 1),


Looking at https://gitlab.com/libtiff/libtiff/-/blob/master/libtiff/tif_dirinfo.c?ref_type=heads#L136, I've concluded "DataType" should be 0 rather than 1.

I've created #9245 to add these four tags.

radarhere · 2025-10-18T10:57:44Z

PIL/TiffTags.py

-LIBTIFF_CORE.remove(320)  # Array of short, crashes
-LIBTIFF_CORE.remove(301)  # Array of short, crashes
-LIBTIFF_CORE.remove(532)  # Array of long, crashes
+LIBTIFF_CORE.remove(330)  # subifd, requires extra support for uint64 payload


Given that #5120 blocked the tag when saving with libtiff, I don't think this is needed anymore.

radarhere · 2025-10-18T11:01:08Z

PIL/TiffTags.py


-LIBTIFF_CORE.remove(320)  # Array of short, crashes
-LIBTIFF_CORE.remove(301)  # Array of short, crashes
-LIBTIFF_CORE.remove(532)  # Array of long, crashes


These were since removed in #5384

radarhere · 2025-10-23T08:28:09Z

All of the tests added here now pass in main.

I've created #9276 to add the last functionality that I think this adds.

wiredfool added Cleanup Do Not Merge TIFF Needs Review labels Dec 13, 2016

wiredfool modified the milestone: 3.5.0 Dec 13, 2016

wiredfool force-pushed the tiff-metadata branch 3 times, most recently from ecf193a to 98268b8 Compare December 14, 2016 12:33

wiredfool added 7 commits December 14, 2016 04:33

initial take of proper tiff metadata support

18b0a37

pulling out special cases, referenceblackwhite works

1ad3dd7

Added support for saving colormaps

8a77275

Tests for issue python-pillow#1765

320884d

Docs

713d383

Whitepoint, Primary Chromaticities working

e1110b5

doc updates

c69500e

wiredfool force-pushed the tiff-metadata branch from 98268b8 to c69500e Compare December 14, 2016 12:34

wiredfool added 2 commits December 14, 2016 07:42

Warning on count or type mismatch on exif data

d79b1d4

Mismatch on count of items, sampleformat is troublesome UNDONE--appro…

5c9de81

…ach?

radarhere modified the milestones: 4.1.0, 4.0.0 Jan 7, 2017

wiredfool mentioned this pull request Jan 20, 2017

Docker images for additional travis runs #2368

Merged

wiredfool modified the milestones: 4.1.0, 4.2.0 Apr 1, 2017

radarhere added the Needs Rebase label Jun 14, 2017

wiredfool removed the Needs Rebase label Jun 21, 2017

radarhere removed this from the 4.2.0 milestone Oct 4, 2017

This was referenced Sep 7, 2018

Convert int values of RATIONAL TIFF tags to floats #3338

Merged

Save compressed TIFF only accepts float values for dpi #1765

Closed

radarhere mentioned this pull request Sep 20, 2018

Corrected TIFF tags #3369

Merged

radarhere added the Needs Rebase label Oct 3, 2018

radarhere reviewed May 25, 2020

View reviewed changes

radarhere mentioned this pull request May 26, 2020

Allow libtiff to write COLORMAP tag #4647

Merged

hugovk force-pushed the master branch from 747e44b to 9e3ad5e Compare December 18, 2020 20:12

radarhere reviewed Aug 1, 2021

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radarhere reviewed Aug 2, 2022

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radarhere reviewed Jul 26, 2025

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radarhere mentioned this pull request Oct 12, 2025

Added four private SGI TIFF tags #9245

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radarhere reviewed Oct 12, 2025

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radarhere reviewed Oct 18, 2025

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radarhere closed this Oct 23, 2025

	PyErr_SetString(PyExc_ValueError, "Requiring 768 items for for Colormap");
	PyErr_SetString(PyExc_ValueError, "Requiring 768 items for Colormap");

	self.assertTrue(len(reloaded.tag_v2[320]), 768)
	self.assertEqual(len(reloaded.tag_v2[320]), 768)

	Pillow currently reads TIFF metadata in pure python and writes either
	Pillow currently reads TIFF metadata in pure Python and writes either

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Libtiff metadata writing fixes #2288

Libtiff metadata writing fixes #2288

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