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2009.01.06 11:04 "Re: How to delete a TIFF image from a Mulit-TIFF file efficiently", by Mark Pereira
Hi Rob,
Thanks for the information. I need to remove the TIFF image that is deleted.
I tried using tiffcp as follows:
int main(int argc, char* argv[])
{
TIFF* in = TIFFOpen (argv[1], "r");
TIFF* out = TIFFOpen (argv[2], "w");
do {
if (current image is not be deleted) then {
tiffcp(in, out);
TIFFWriteDirectory(out);
}
}
while (TIFFReadDirectory(in));
TIFFClose(out);
}
It works fine but its not linear and seems have complexity O(N x N).
I ran gprof and most of the time is spent in TIFFLinkDirectory(). Seems
like each time TIFFWriteDirectory() is called all the directory entries
are traversed to link the last directory that is written and sort of
explains the non linear behavior.
Please comment on this analysis. Is there any way in which this linking
can be done more efficiently.
Mark
rob.tillaart@chello.nl wrote:
> Hi Mark,
>
> A Multipage TIFF is a chain of images linked to each other. The most time
> efficient way to delete an image is get them out of the list. To do this
> one must change the "pointer" to the image to the one that's next in the
> file.
>
> In pseudo code: previous_image.next = to_be_deleted_image.next
>
> This is very fast but the complete image with all tags is kept in the
> file, increasing the slack%.
>
> sofar my 2 cents,
> rob tillaart
>
> ---- Mark Pereira <mark@softjin.com> schreef:
>
>> Hi,
>>
>> I would like to know an efficient way of deleting a TIFF image from a
>> Multi-TIFF file?
>>
>> Currently I am doing a tiffsplit followed by a merge (tiffcp). This
>> works fine but its extremely in-efficient
>>
>> Thanks,
>> Mark
>>
>
>
>
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