2023.04.12 15:14 "[Tiff] TIffWriteDirectory() causes problems", by David
C. Partridge
Thread
2023.04.12 15:14 "[Tiff] TIffWriteDirectory() causes problems", by David C. Partridge
So the code I have to open a TIFF file ends as follows:
//
// Now that all the EXIF tags are written, need to write the EXIF
// custom directory into the file...
//
// WriteCustomDirectory returns the actual offset of the EXIF directory.
//
TIFFWriteCustomDirectory(m_tiff, &dir_offset_EXIF);
// Go back to the first (main) directory, and set correct value of the
// EXIFIFD pointer. Note that the directory is reloaded from the file!
//
TIFFSetDirectory(m_tiff, 0);
TIFFSetField(m_tiff, TIFFTAG_EXIFIFD, dir_offset_EXIF);
}
else
{
TIFFClose(m_tiff);
m_tiff = nullptr;
};
};
return bResult;
};
m_tiff should still be valid on exit
I also have code to write the image data:
Which starts like:
bool CTIFFWriter::Write()
{
ZFUNCTRACE_RUNTIME();
bool bResult = false;
bool bError = false;
//
// Multipliers of 256.0 and 65536.0 were not correct and resulted in a fully saturated
// pixel being written with a value of zero because the value overflowed the data type
// which was being stored. Change the code to use UCHAR_MAX and USHRT_MAX
//
if (m_tiff)
{
tmsize_t scanLineSize;
tdata_t buff;
scanLineSize = TIFFScanlineSize(m_tiff);
That works but ends up with the root IFD being written at the end of the file what TIFFClose calls TIFFReWriteDirectory().
If I insert TIFFWriteDIrectory(m_tiff); immediately after the line that reads TIFFSetField(m_tiff, TIFFTAG_EXIFID, dir_offset_EXIF);
then when I call into Write the value returned by TiffScanlinesSize() is ZERO!
WHY is that and what can/should it do to fix this
Thanks, David