Decoding jpeg string

[BruceAmmons]

Here is the original code, updated to the newer Vision controls.  The only functions I really use are encode and decode, but I included the whole library.  You can replace the encode with the IMAQ Write String, but for some reason NI has not provided an IMAQ Read String to complement it.  I would like them to do so, but they seem fairly resistant for some unknown reason.  Perhaps in the next version.

Bruce

[waldemar.hersacher]

Bruce thank you for providing the library again. I know they are sometimes resistant against any changes.

[Jean-Philippe]

Bruce,

Thanx for the IMAQ JPEG Decode.vi but there seems to be a big memory leak in your dll.

I slightly modified the demo code and introduced a while loop: in the Task manager I observe the memory usage going continuously up and Labview is crashing after a short while.

best regards,

Jean-Philippe

[BruceAmmons]

Hmm, I never noticed that.  I will have to do some testing myself before I use it again.  I haven't had any problem with it, though.  Perhaps the memory leak is very slow.  For the record, I didn't write the code.  I just downloaded it from NI a long time ago.

Depending on what you are trying to do, NI now has the ability to read/write images to strings using flatten to string.  Unfortunately, they use a proprietary format for the strings so you can't read the files from any other program.  However, they work well if you stay within LabVIEW.  I keep suggesting they implement a JPEG string to image, but they don't think anybody would use it.  Perhaps if other people submitted product suggestions, they would realize that it would be a useful feature.

Bruce

[Jean-Philippe]

Hi Bruce,

Thx for your input.

It seems that the leaking pb (massive in my case) occurs only with RGB images.

I looked around and found another thread speaking of that pb: 

http://forums.ni.com/ni/board/message?board.id=170&message.id=325881&requireLogin=False

Since I wanted to transfer a compressed image over the net I will use the solution (flatten_image_to_string_lv70.vi) discussed here:

http://sine.ni.com/devzone/cda/epd/p/id/3314

regards,

JPh

[BruceAmmons]

That explains it.  I have never tried anything but grayscale images, for which it works fine with no memory leak.

I didn't realize flatten image to string has been around since LV 7.  I thought it was introduced around 8.0.  Or are you using a different function?

Bruce

[Jean-Philippe]

Bruce,

I will use the solution with flatten image to string and "IMAQ Remote Compression".

I tried and it seems to work fine with RGB images.

Cheers,

JPh