2017.08.26 14:19 "Re: [Tiff] Determining use of "w" or "w8" in TIFFOpen", by John

Hello Paul,

On 26 August 2017 at 14:56, Paul Hemmer <paulhemmer@hotmail.com> wrote:

If that size is greater than 4GB, I should specify "w8" and if less than, I should specify "w" when calling TIFFOpen() in order to get the BigTIFF format when needed.

But what if the use of COMPRESSION_LZW would result in a file that is much smaller than 4GB? I can't know that ahead of time (can I?) Should I still use w8 if the uncompressed dimensions require more than 4GB?

I handle this by enabling bigtiff mode automatically if I'm writing an uncompressed TIFF which will be over 4GB. If compression is turned on, users have to tick a box (or pass an option) to enable bigtiff write. It's a bit unsatisfactory.

I'm finding that I can't simply specify "w8" for all, as those that are less than 4GB end up failing to open.

They should only fail to open if the program you are using does not support bigtiff.

Sadly, rather few programs support bigtiff, hence the need to have it as an option that users must explicitly turn on.

John