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#1 Posted : Thursday, March 12, 2009 3:04:00 PM(UTC)

mezzmo  
mezzmo

Groups: Registered
Posts: 6


Hello,

Can someone please advise me on the CMP header size? I'm doing hashing on the first few bytes of images and I want it to be as optimal as possible, but of course I need to hash at least the header + some image data. Unfortunately I don't know the header size, so can't really make this an optimal number.

Thanks in advance!

   Dennis

 

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#2 Posted : Sunday, March 15, 2009 6:41:21 AM(UTC)
Maen Hasan

Groups: Registered, Tech Support
Posts: 1,328

Was thanked: 1 time(s) in 1 post(s)

Dennis,

The structure of CMP header and image data is not published. Although you could try to deduct some information about it, for example by storing small files (like 1 pixel to 10 pixels in size), we don't recommend you base your work on any results you obtain this way. Since the header details are not documented, our engineers are at liberty to make any changes to the format in the future as long as they maintain compatibility with images saved by older versions.

This means our official recommendation is to make no assumptions about the header length or contents.

Thanks,
Maen Badwan
LEADTOOLS Technical Support
 
#3 Posted : Sunday, March 15, 2009 2:22:50 PM(UTC)

mezzmo  
mezzmo

Groups: Registered
Posts: 6


I understand. I just need to know whether it's smaller than (for example) 512 bytes or not. And if not, is smaller than 1024, etc... I don't actually need the exact byte count, as I work in data chunks anyway, so I'll have to align them to the next largest chunk size.

Thanks,

   Dennis
 
#4 Posted : Monday, March 16, 2009 6:49:47 AM(UTC)
Maen Hasan

Groups: Registered, Tech Support
Posts: 1,328

Was thanked: 1 time(s) in 1 post(s)

Dennis,

I saved a number of very small images (between 1 and 70 pixels total size) as CMP, and all of them had a size that ranged between 600 and 700 bytes. This means the header is definitely smaller than 1024 bytes, but like I wrote last time, there's no guarantee it won't change in the future.

Thanks,
Maen Badwan
LEADTOOLS Technical Support
 
#5 Posted : Monday, March 16, 2009 1:28:47 PM(UTC)

mezzmo  
mezzmo

Groups: Registered
Posts: 6


Thank you - I understand that, but knowing that it's smaller than 1024 bytes is enough for me at the moment.
 
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