Embedding additional txt in a PNG file (IMAQ 8.2)

[Neville D]

Hi all,

Is there a way to embed some additional text information to a png image file? I want to be able to save some image crop information to the image to avoid having to maintain an additional file.

There seem to be some VI's "IMAQ Write Custom Data" and "IMAQ Read Custom Data", but they don't seem to be able to save the information to the png file.

Anybody know what those specific VI's are for?

Thanks,

Neville

[crelf]

QUOTE(Neville D @ Apr 25 2007, 05:23 AM)

There seem to be some VI's "IMAQ Write Custom Data" and "IMAQ Read Custom Data", but they don't seem to be able to save the information to the png file.

Right - I *think* those VIs are only for embedding extra data in a jpg file.

PS: Ever had a jpg emailed to you that was a relatively small image on screen, yet the file size was large? It could have had some data embedded in there. It's not an uncommon quasi-encryptive technique called steganography, where you can store heaps of stuff in there - including other images You can find out more about steganography in gerenal here, including some info on digital media steganography.

[eaolson]

QUOTE(crelf @ Apr 24 2007, 03:31 PM)

Right - I *think* those VIs are only for embedding extra data in a jpg file.

http://forums.ni.com/ni/board/message?board.id=170&message.id=123262&requireLogin=False' target="_blank">This thread from the NI forums suggests that they can write metadata to a png.

[Neville D]

QUOTE(eaolson @ Apr 24 2007, 03:01 PM)

http://forums.ni.com/ni/board/message?board.id=170&message.id=123262&requireLogin=False' target="_blank">This thread from the NI forums suggests that they can write metadata to a png.

Hmm.. I seem to be able to write the data and read it, while the image buffer is maintained.

But saving the image doesn't seem to save the meta data as well.

Silly me!! There is a SEPARATE VI "IMAQ Read image and vision info".. the regular "IMAQ Read Image" won't work..

Neville.

[crelf]

QUOTE(Neville D @ Apr 25 2007, 09:19 AM)

There is a SEPARATE VI "IMAQ Read image and vision info".. the regular "IMAQ Read Image" won't work..

Cool :thumbup:

[LAVA 1.0 Content]

The detailed help also points 2 example applications :

• Examples\Vision\3. Applications\Battery Clamp Inspection Example.vi
  
• Examples\Vision\2. Functions\Calibration\Simple Calibration Example.llb
  

They demonstates the way to use these metadata which, apparently, can only be "overlay information, pattern matching template information, and calibration information"

Hope this helps