how to read a image's raw pixel infomation?

[IgG]

dear all,

right now i got a problem to read raw pixel information from a image grabbed by a vedio camera.
since the time stamp by the vedio camera is encoded in the each frame image's first 14 pixels.

i'm using "IMAQ GetRowCol.vi" to extract the 14 pixel information, but i only get the intensity value of that pixels.
i'm not sure if the intesity value indeed is the image's raw data.

if not, how could I extract the raw data from the image pixel to get those encoded timestamp?

thank you very much,

best,

Jack

[Nacree]

You might try the read JPG file.vi

It give you access to the other information in the image data.  Don't know if it will give you the timestamp data though.

-Nathan

[IgG]

Hi, Nathan,
thank you very much for your help
but my image data is directly from the camera.
is this type of data  so called the "raw " file? it should be different from jpg or bmp file, shouldn't it?
if so, how could i extract the raw info?

thanks,

Jack

[tst]

If you search for "raw image" or "raw file" you should find quite a few results.

If my understanding is correct, then there is no properly defined standard for these formats, so you are probably left to analyze the binary structure of the file on your own.

[IgG]

hi, tst

thank you so much for your reply
as you said, the BCD time stampe encoded in the image can't not be extracted out only by read out intensity infomation?
we have to read out the binary info by other way?

this binary info doesn't encode the intensity value, does it?

thanks

Jack

[RavensFan]

I think there may be a misunderstanding as to what Jack is trying to accomplish.

My interpretation is that the image has the time stamp in the picture itself like a watermark.  And he wants to extract the text out of the image.   While the replies to date have been interpreting this as the time code like that saved in the meta data of a jpeg file.

Never mind, I just reread the first message and it mentioned 14 pixels.  That wouldn't be enough to have any kind of readable text in the image.

Message Edited by Ravens Fan on 01-30-2007 09:36 AM

[IgG]

Hi, Ravens &all

thank you very much for your interpretation.
i guess it might be my fault not being able to discribe my problems clearly.
this is my case: each frame image from my camera is 16bit gray scale.
but only 8 bits are used to encode the timestamp. and firt 14 pixels of each frame image is used to code 28 digits timestamp information.
and the format of the BCD coding is attached as the pictures

now i'm just confused whether the intensity value represents the real raw data stored in each frame image?

thanks,

jack

[J.Harv]

jack-

       I would use ImagetoArray. This will give you all of the raw data, rather than just for a row or column. Then once you know how many pixels it will be across you will be able to see exactly which numbers are the timestamp and extract those out. But in answer to your question, yes, those numbers do represent the raw data.  The numbers are signed 16-bit numbers and represent the intensity.  Sounds like you are on the right track.  Let us know if you have any questions.

Regards,

John H
Applications Engineer
National Instruments
http://www.ni.com/support