空间滤波（掩模操作）

空间滤波就是由利用某像素周围的像素值和掩模矩阵来确定该像素的新值

1. 基础方法

void Sharpen(const Mat& myImage,Mat& Result)
{
    CV_Assert(myImage.depth() == CV_8U);  // accept only uchar images
    const int nChannels = myImage.channels();
    Result.create(myImage.size(),myImage.type());
    for(int j = 1 ; j < myImage.rows-1; ++j)
    {
        const uchar* previous = myImage.ptr<uchar>(j - 1);
        const uchar* current  = myImage.ptr<uchar>(j    );
        const uchar* next     = myImage.ptr<uchar>(j + 1);
        uchar* output = Result.ptr<uchar>(j);
        for(int i= nChannels;i < nChannels*(myImage.cols-1); ++i)
        {
            *output++ = saturate_cast<uchar>(5*current[i]
                         -current[i-nChannels] - current[i+nChannels] - previous[i] - next[i]);
        }
    }
    Result.row(0).setTo(Scalar(0));
    Result.row(Result.rows-1).setTo(Scalar(0));
    Result.col(0).setTo(Scalar(0));
    Result.col(Result.cols-1).setTo(Scalar(0));
}

• 关于Mat.depth()

#define CV_8U 0
#define CV_8S 1
#define CV_64F 6

• 图像的一行存储一般是连续的

2. The filter2D function

Mat kernel = (Mat_<char>(3,3) <<  0, -1,  0,
                                   -1,  5, -1,
                                    0, -1,  0);

filter2D( src, dst1, src.depth(), kernel );

非常常用，可以设计自己的滤波器。