Re: Re: PCA - What next!?

Hi, I guess it should be because you did not cast to uchar.
Rather, I everytime think as why Ipl stores data as char not uchar....

Fadi Chakik wrote:
> I used the PCA.zip without changing the code.
>   
>   All I did is to add a loop to print the avg values like:
>   
>   for(i=0; i<avg->height; i+=10)
> {
>    for(j=(avg->widthStep)*i; j<(avg->widthStep)*(i+1);
>          j+=avg->nChannels)
>    {
>       printf("\nAVG: %d, %d, %d\n", avg->imageData[j], 
> avg->imageData[j+1], avg->imageData[j+2]);;
>      
>      }
>   }
>   
>   -Fadi
> 
> Parameswaran <cegparamesh@xxxxxxxxx> wrote:
>   No! Average values cannot be negative.
> There is some problem with your code. I didnt experience a negative
> value..
> 
> In order to display the image, you have to normalize the pixel values
> between 0 and 255, and then store it in a 8 bit image.
> Only 8 bit images can be displayed correctly in the Highgui window, i
> suppose..
> 
> Regards, :D
> Paramesh.
> 
> --- In OpenCV@xxxxxxxxxxxxxxx, Fadi Chakik <fadichakik@...> wrote:
>  >
>  > in the code inside the PCA.zip file, there is "avg" variable which
> defines the images 'pixels average.
>  >   I tried to print it to see its value, I can see that avg has some
> negative values.. is that normal!
>  >   the images from which "avg" is calculated are all gray levels..
> that means values of pixels are between 0..255. So the mean of
> positive values should be positive! why do we find negative values for
> "avg"? is there any explanation?
>  >   
>  >   However, in the HIGUI window showing the projection, I get
> sometimes black images for some of the projection.
>  >   
>  >   -Fadi
>  >
>  > Parameswaran <cegparamesh@...> wrote:
>  >   There are many available techniques for face recognition, which can be
>  > found in the face recognition homepage:
>  > www.face-rec.org
>  >
>  > The simplest and best approach is PCA or eigenfaces approach, which
>  > can be used either to recognize, or to reduce the dimensionality.
>  >
>  > To recognize using the weights, you can use euclidean distance,
>  > Correlation distance, covariance distance, and many other distances
>  > available.
>  >
>  > TO save the bounding rectangle of a face, you have to set the Image
>  > Region of Interest(ROI) and save the image.
>  > After saving, reset the ROI.
>  >
>  > Regards, :D
>  > Paramesh.
>  >
>  > --- In OpenCV@xxxxxxxxxxxxxxx, "kirkl_tamworth" <kirkl_tamworth@>
>  > wrote:
>  > >
>  > > Hi all,
>  > >
>  > > I have successfully compiled the PCA example provided in the files
>  > > section, which outputs the eigenvalues and such. I have two queries:
>  > >
>  > > 1. Can you help me with where I go from here to perform face-
>  > > recognition? I have 25 face images ready to use and would greatly
>  > > appreciate some help with completing the Eigenface approach.
>  > >
>  > > 2. I have also managed to incorporate the face detection sample
> into a
>  > > C# application, but I'm not sure how to extract the face from the
>  > > image, given that I know the bounding rectangle. Is there an OpenCV
>  > > function that can do this for me?
>  > >
>  > > My first query is much more important than the second and I would
>  > > really, really appreciate some help with this. Thanks.
>  > >
>  > > Kirk
>  > >
>  >
>  >
>  >
>  >
>  >
>  >
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