To get the R, G, B values of a pixel from a packed or interlaced frame

#define BCHANNEL 0
#define GCHANNEL 1
#define RCHANNEL 2
unsigned char Clip(int iVal)
{
 return ( iVal > 255 ? 255 : ( iVal < 0 ) ? 0 : iVal) ;
}

//Pixel Functions
int GetValue(int iX, int iY, int iImageWidth, int iImageHeight, int iChannel, int iBPP, BYTE *pbySrc)
{
 Clip(iX);
 Clip(iY);
 return pbySrc[iY * iImageWidth * iBPP + iX * iBPP + iChannel];
}

int GetValueR(int iX, int iY, int iImageWidth, int iImageHeight, int iBPP, BYTE *pbySrc)
{
 return GetValue(iX, iY, iImageWidth, iImageHeight, RCHANNEL, iBPP,pbySrc);
}

int GetValueG(int iX, int iY, int iImageWidth, int iImageHeight, int iBPP, BYTE *pbySrc)
{
 return GetValue(iX, iY, iImageWidth, iImageHeight, GCHANNEL, iBPP, pbySrc);
}

int GetValueB(int iX, int iY, int iImageWidth, int iImageHeight, int iBPP, BYTE *pbySrc)
{
 return GetValue(iX, iY, iImageWidth, iImageHeight, BCHANNEL, iBPP, pbySrc);
}

Here the iX and iY values are the pixel positions
iImageWidth  -> Width of the Image
iImageHeight -> Height of the Image
iBPP                -> Bytes per pixel ie bitsperPixel/8. For eg. RGB 24 it is 3.
pbySrc            -> Address of the Source buffer

Call the GetValueR() for Red value of a pixel, Call the GetValueG() for Green value of a pixel and Call the GetValueB() for Blue value of a pixel from your application.

NB: These functions are applicatoion for interlaced fromat or packed RGB formats and not for the planar formats