2006.08.04 14:48 "Re: [Tiff] newbiequestion: [?] backup complete ifd > private ifd", by Gerben Vos

Karin Hoehne wrote:

> [2]

and in the very end, what i want to have is:

| header | ifd[0] | data | ifd[1] (=exact! copy of ifd[0]) |

[3]

i want to backup the ifd[0] >one< time and just leave it in what ever position in the file. since ifd[0] does not have any pointers to the backuped ifd[1], there shouldn't be any problems with the file, because ifd[1] is just a chunk of data. am i right with that assumption?

Correct.

with every loading-function (in the to-be-programmed app) i want compare >every< (numerical) value of ifd[0] and the backup ifd[1]. if >anything< is different (e.g. a single bit), i want to copy the values of ifd[1] to ifd[0].

Note that programs that change ifd[0] will be very likely to destroy or overwrite ifd[1]. I don't understand what it is you are trying to accomplish, but maybe you will want to store ifd[1] in a separate file.

i have to admit: it was mentioned and i know, thet i >can< somehow copy the ifd, but i still couldn't figue aut >how<. (sorry... newbie)

Libtiff can't really help you with that. Best is to write a program yourself that follows the IFD chain. See the code of tiffdump for an example; it is a lower-level utility than tiffinfo and doesn't even use libtiff. It should be easy to adapt its code to give you a hexdump of the IFD.

Gerben Vos.

--

I will be on holiday next week.