sobel算子，亲测，好用

#define EXTRA_NAME "@sobeledge."
#include "loadbmp.h"

#define Point(x,y) lpPoints[(x)+(y)*nWidth]
#define Point1(x,y) lpPoints1[(x)+(y)*nWidth]

void Sobel()
{
int x,y,x1,y1,i;
BYTE *lpPoints=new BYTE[nWidth*nHeight];
BYTE *lpPoints1=new BYTE[nWidth*nHeight];
memset(lpPoints1,0,nWidth*nHeight);
GetPoints(lpPoints);

int d,max;
static s[8][9]={
{-1,-2,-1,0,0,0,1,2,1},
{0,-1,-2,1,0,-1,2,1,0},
{1,0,-1,2,0,-2,1,0,-1},
{2,1,0,1,0,-1,0,-1,-2},
{1,2,1,0,0,0,-1,-2,-1},
{0,1,2,-1,0,1,-2,-1,0},
{-1,0,1,-2,0,2,-1,0,1},
{-2,-1,0,-1,0,1,0,1,2}
};
for(y=1;y<nHeight-1;y++)
{
for(x=1;x<nWidth-1;x++)
{
max=0;