saturate_cast()就是防止数据溢出,具体的原理可以大致描述如下:
if(data<0)
data=0;
if(data>255)
data=255
//使用图像混合例子中的C语言版本演示
for (int i=0; i<src1.rows; i++)
{
const uchar* src1_ptr = src1.ptr<uchar>(i);
const uchar* src2_ptr = src2.ptr<uchar>(i);
uchar* dst_ptr = dst.ptr<uchar>(i);
for (int j=0; j<src1.cols*nChannels; j++)
{
dst_ptr[j] = saturate_cast<uchar>(src1_ptr[j]*alpha + src2_ptr[j]*beta + gama);//gama = -100, alpha = beta = 0.5
// dst_ptr[j] = (src1_ptr[j]*alpha + src2_ptr[j]*beta + gama);
}
}
imshow("output2",dst);
这里加入了溢出保护,结果如下
//没加入溢出保护
for (int i=0; i<src1.rows; i++) { const uchar* src1_ptr = src1.ptr<uchar>(i); const uchar* src2_ptr = src2.ptr<uchar>(i); uchar* dst_ptr = dst.ptr<uchar>(i); for (int j=0; j<src1.cols*nChannels; j++) { //dst_ptr[j] = saturate_cast<uchar>(src1_ptr[j]*alpha + src2_ptr[j]*beta + gama);//gama = -100, alpha = beta = 0.5 dst_ptr[j] = (src1_ptr[j]*alpha + src2_ptr[j]*beta + gama); } } imshow("output2",dst);
if(data<0)
data=0;
else if(data>255)
data=255;