[ros-users] cvMat -> ros message

[Dan Lazewatsky]

On 4/22/10 8:19 PM, Patrick Mihelich wrote:
> What is the type of the data in your cvMat? I assume it's either float 
> or double?
I probably should have included the line where the cvMat was declared.
CvMat _h = cvMat(3, 3, CV_64F, h);
>
> Are the publisher and subscriber on the same machine?
They are
>
> I suspect you meant h_m.mat[j*3+k], but that doesn't explain the 
> totally wrong numbers.
>
> Right before your publish() call, can you print out the contents of 
> h_m.mat and check that they're correct.
If I print out the numbers before publishing, they are indeed correct.
>
> As an aside, the new C++ interface 
> <http://opencv.willowgarage.com/documentation/cpp/introduction.html> 
> to OpenCV is a big improvement over cvMat/IplImage if you like 
> niceties like type safety, automatic freeing of memory and more 
> succinct code.
Awesome, I didn't know about that!
>
> -Patrick
>
> On Thu, Apr 22, 2010 at 5:52 PM, Dan Lazewatsky 
> <lazewatskyd at cse.wustl.edu <mailto:lazewatskyd at cse.wustl.edu>> wrote:
>
>     Hi all -
>     I have a cvMat that I'm trying to send out in a ROS message, but I'm
>     having some issues getting it to work right.
>
>     My message definition is: float64[9] mat
>     I'm loading data into the message as follows:
>     myMessage h_m;
>     for(int j=0; j<3;++j){
>         for(int k=0; k<3; ++k){
>             h_m.mat[j+k*3] = cvmGet(&_h, j, k);
>         }
>     }
>
>     No errors here, but when I look at the data from a subscriber (or
>     using
>     rostopic echo), but numbers are wrong. Numbers that should be in the
>     range of 0-10 end up in 10^6-10^-5. I've tried creating a
>     std_msgs::Float64 and casting to a Float64 first, neither of which
>     worked. I'm at a bit of a loss as to what's going on. Any help
>     would be
>     appreciated.
>
>     Thanks,
>     -Dan
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