ExifTag.TimeZoneOffset is defined as uint[], but the TIFF spec defines it as signed short #2437
Description
Prerequisites
- I have written a descriptive issue title
- I have verified that I am running the latest version of ImageSharp
- I have verified if the problem exist in both
DEBUGandRELEASEmode - I have searched open and closed issues to ensure it has not already been reported
ImageSharp version
3.0.1
Other ImageSharp packages and versions
?
Environment (Operating system, version and so on)
Windows 10 x64
.NET Framework version
.NET 7
Description
The TimeZoneOffset Exif tag is defined in the code as a uint[] (
)However, the specifications for TIFF/EP which defines that tag seem to require a signed short (optionally two signed shorts). See Page 19 and 40 of the TIFF/EP spec : https://web.archive.org/web/20060212163025/http://www.map.tu.chiba-u.ac.jp/IEC/100/TA2/recdoc/N4378.pdf
This requirement is also encoded in the TIFF verification code in JHove, which then flags the file as non-conformant (https://jhove.openpreservation.org/modules/tiff/tags/ , https://jhove.openpreservation.org/)
As a side note, since ExifTag doesn't have a public constructor, I cannot create my own tags to work around this issue (or to add custom tags to the file).
Steps to Reproduce
Set the DateTimeOffsetTag in a tiff file, then save the file
var image = Image.Load(sourceTifFile);
image.Frames[0].Metadata.ExifProfile = new ExifProfile();
image.Frames[0].Metadata.ExifProfile.SetValue(ExifTag.TimeZoneOffset, new uint[] {1});
image.Save(outputTifFile);
Now run the output tiff file through jhove verification
robin@ubuntu:~$ jhove -m TIFF-hul Output.tif
Jhove (Rel. 1.20.0, 2019-01-19)
Date: 2023-04-13 13:33:05 PDT
RepresentationInformation: Output.tif
ReportingModule: TIFF-hul, Rel. 1.8 (2017-05-11)
LastModified: 2023-04-13 13:27:13 PDT
Size: 343128
Format: TIFF
Status: Not well-formed
SignatureMatches:
TIFF-hul
ErrorMessage: Type mismatch for tag 34858; expecting 8, saw 4
MIMEtype: image/tiff
You can install jhove on an ubuntu box with
sudo apt-get install jhove default-jre
Note: I ran the ImageSharp test code on Windows, just used Ubuntu for testing as the jhove install is easier
Images
No response