Dave,
You will have to determine precisely what you're being given to work
with. Then either study the official JPEG/JFIF Standards, find the
standard that governs the file you're reading and from that determine
precisely where within the file the info is stored, and extract it...
(the Standards are not light reading)
OR
simply ask the file creator/publisher where in the file is the data
OR
do it the way I did it once by converting the entire file to ASCII and
examining the result.
Once you have the required offset the rest will be relatively
straightforward.
Years ago as part of a larger job I had to determine the exact
dimensions of a JPEG/JFIF so that a VFP window could be created, for
display etc.
I avoided the search through the official JPEG Standards; that would
have been a nightmare. Instead, using VFP low-level functions I
converted the entire file from HEX to ASCII, found what I thought looked
like the dimensions (in pixels from memory) and then ran the same test
on many other files. They all had the same info stored at exactly the
same offset and the rest of the job was easy.
Since QR codes are relatively new, I think you'll have more luck with
the file publisher - they MUST know exactly where in the file this data
is being placed, and it will be consistent. It's possible the official
Standards haven't even caught up with the outside world, so I would
begin with the file creator/publisher anyway.
GaryT
On 20/11/12 02:59, Dave Crozier wrote:
I have developed a QR Code print/read application in C# including a library
that does all the encoding/decoding. I use a canvas to produce the QR code on
and can decrypt a QR code embedded in a JPG or PNG.
I now want to produce an ActiveX/dll that VFP can use in reportsin order to
print out QR codes on a VFP report and I'm at a loss on how/what to pass back
to VFP from the ActiveX.
As for the physical activeX, I have no problem creating it in C# and have a
template that can send back numerics or strings as properties in the ActiveX
from C# so that VFP can receive them, I just have no idea where to look to get
an feel for what I should send back to VFP e.g Stream, string etc. Any ideas,
or help on where to look?
Dave
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