類似度--歐氏距離（歸一化）

<!-- lang: cpp -->
double CalcSimilarity(IplImage* S,IplImage* T)

{ double r = 0.f; int width = T->width; int height = T->height;

uchar* ptrS = NULL;
uchar* ptrT = NULL;
float a = 0,b = 0,c = 0;
for(int i=0;i<height;i++)
{
	ptrS = (uchar*)S->imageData+i*S->widthStep;
	ptrT = (uchar*)T->imageData+i*T->widthStep;
	for(int j=0;j<width;j++)
	{
		a += ptrS[j]*ptrS[j];
		c += ptrT[j]*ptrT[j];
		b += ptrS[j]*ptrT[j];
	}
}

return b / (sqrt(a) * sqrt(c));

}