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2012.05.18 13:23 "[Tiff] TIFFGetField: count should be uint32_t (Bug in documentation)", by Sandro Mani
2012.05.18 14:27 "Re: [Tiff] TIFFGetField: count should be uint32_t (Bug in documentation)", by Bob Friesenhahn
2012.06.27 15:12 "[Tiff] variable sized tags and passcount", by David Hoese

2012.05.18 13:23 "[Tiff] TIFFGetField: count should be uint32_t (Bug in documentation)", by Sandro Mani

Hello,

according to [1], when querying multi-valued fields with TiffGetField, count should be of a 16-bit unsigned integer. However, in various places in the source libtiff source code, a 32-bit unsigned integer is used. Indeed, a nasty bug I encountered was caused by count being 16 bits wide:

  uint16_t count;
  uint32_t width;
  void* data;
  std::cout<<&width<<" "<<&count<<std::endl;

  TIFFGetField(tif, TIFFTAG_IMAGEWIDTH, &width);
  std::cout<<width<<std::endl;

  TIFFGetField(tif, TIFFTAG_MODELTIEPOINT, &count, &data);
  std::cout<<width<<std::endl;

Output:
0x7fffa4d38a68 0x7fffa4d38a66
7721
0
=> Count overflowed into width

If my analysis is correct, I guess the documentation should be fixed.

Thanks,
Sandro

[1] http://www.remotesensing.org/libtiff/man/TIFFGetField.3tiff.html