Re: Re: How to access pixels - urgent question

Or, if you prefer...
   
  uchar getPixel( IplImage*img, int lin, int col, int channel ) {
   return ((uchar*)(img->imageData + img->widthStep*lin))[col+channel] ; 
}
   
  Where channel is 0 to first channel, 1 to second, etc...
   
  Regards, 
   
  Luiz Reginaldo

Parameswaran <cegparamesh@xxxxxxxxx> escreveu:
  The FAQs would say it all...


Suppose, we have 8-bit 3-channel image I (IplImage* img):

I(x,y)blue ~ ((uchar*)(img->imageData + img->widthStep*y))[x*3]
I(x,y)green ~ ((uchar*)(img->imageData + img->widthStep*y))[x*3+1]
I(x,y)red ~ ((uchar*)(img->imageData + img->widthStep*y))[x*3+2]


Regards, :D
Paramesh.

--- In OpenCV@xxxxxxxxxxxxxxx, "shadi_moudallal" <shadi_moudallal@...>
wrote:
>
> Hi,
> i think this code is great but i need it to work for multi channel 
> image. How can i use the iplgetpixel or if this code can be changed 
> to work for multi channel image.
> thx
> 
> --- In OpenCV@xxxxxxxxxxxxxxx, Luiz Curado <lutitus@> wrote:
> >
> > So, lets go in that code...
> >    
> >   uchar getPixel( IplImage*img, int lin, int col ) {
> >    return ((uchar*)(img->imageData + img->widthStep*lin))[col] ; 
> > }
> >    
> >   - uchar is a unsigned char type (8 bits)
> >   - img is a pointer to my IplImage
> >   - lin, col are the line and column of the pixel
> >   - imageDate is an "array" that contains the pixels: first line, 
> second line, etc, all in the same "array"
> >   - img->widhStep is the size of each line in my IplImage
> >    
> >   Now, it becomes more clear, dont? 
> >    
> >   img->imageData + img->widthStep*lin
> >    
> >   => With this piece of code, i'm in the beggining of line "lin"
> >    
> >   <my line>[col] ; 
> >    
> >   => With this piece of code, i'm in the column "col" of 
> line "lin" 
> >    
> >   I hope this can help. :)
> >    
> >   Regards,
> >    
> >   Luiz Reginaldo
> > 
> > evaspies <evaspies@> escreveu:
> >   Hi Luis,
> > 
> > thanx for your help.
> > But I dont quite understand this!
> > 
> > can you please comment that code?`
> > 
> > Thnx a lot
> > 
> > 
> > 
> > --- In OpenCV@xxxxxxxxxxxxxxx, Luiz Curado <lutitus@> wrote:
> > >
> > >   Hi, 
> > >    
> > >   Try this:
> > >    
> > >   uchar getPixel( IplImage*img, int lin, int col ) {
> > >   return ((uchar*)(img->imageData + img->widthStep*lin))[col] ; 
> > >   }
> > >    
> > >   void setPixel( IplImage*img, int lin, int col, uchar valor ) {
> > >   ((uchar*)(img->imageData + img->widthStep*lin))[col] = valor ;
> > >   }
> > >   
> > > Regards,
> > >    
> > >   Luiz Reginaldo
> > >   
> > > evaspies <evaspies@> escreveu:
> > >   Hi guys.
> > > 
> > > Im trying to access Pixels of a grayscale image to get a
> > > representantive   value. best of all would be if the value lies
> > > between 0 für black and 255 für white.
> > > Do you have an Idea?
> > > I tried to use iplGetPixel, but that function is only for 3 or 4
> > > channel pictures.
> > > 
> > > Thanx for xour help!
> > > 
> > > 
> > > 
> > > 
> > > 
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