Susan Corner Detector实施 [英] Susan Corner Detector implementation

问题描述

我还没有理解代码和函数的处理方式..

I have not understood the code and the way function is handled..

你能否详细说明函数声明

can you elaborate the function declaration

fun = @(img) susanFun(img);
map = nlfilter(img,maskSz,fun);

同样在苏珊角落检测器中，我们只有2个阈值..t和g..但是这里我们有thGeo，thGeo1，thGeo2，thT，thT1

Also in susan corner detector we have only 2 threshold values.. "t and g".. but here we have "thGeo,thGeo1,thGeo2,thT,thT1"

我无法理解这里使用的方法：

I am not able to understand the method employed here:

function [ map r c ] = susanCorner( img )
%SUSAN Corner detection using SUSAN method.
%   [R C] = SUSAN(IMG)  Rows and columns of corner points are returned.


maskSz = [7 7];
fun = @(img) susanFun(img);
map = nlfilter(img,maskSz,fun);
[r c] = find(map);

end

function res = susanFun(img)
% SUSANFUN  Determine if the center of the image patch IMG
%   is corner(res = 1) or not(res = 0)


mask = [...
    0 0 1 1 1 0 0
    0 1 1 1 1 1 0
    1 1 1 1 1 1 1
    1 1 1 1 1 1 1
    1 1 1 1 1 1 1
    0 1 1 1 1 1 0
    0 0 1 1 1 0 0];

% uses 2 thresholds to distinguish corners from edges
thGeo = (nnz(mask)-1)*.2;
thGeo1 = (nnz(mask)-1)*.4;
thGeo2 = (nnz(mask)-1)*.4;
thT = .07;
thT1 = .04;

sz = size(img,1);
usan = ones(sz)*img(round(sz/2),round(sz/2));

similar = (abs(usan-img)<thT);
similar = similar.*mask;
res = sum(similar(:));
if res < thGeo
    dark = nnz((img-usan<-thT1).*mask);
    bright = nnz((img-usan>thT1).*mask);
    res = min(dark,bright)<thGeo1 && max(dark,bright)>thGeo2;

else
    res = 0;
end

end

推荐答案

fun = @(img) susanFun(img);
map = nlfilter(img,maskSz,fun);

表示

• fun 是函数的句柄（或指针）。


• @（img）说 fun 接受一个名为 img 的参数。


• susanFun（img）是的主体乐趣

• fun is a handle (or pointer) to a function.
• @(img) says fun takes an argument called img.
• susanFun(img) is the body of fun

nlfilter 传递函数句柄 fun 并可以调用它。
实际上，它会将 fun 与参数 img 一起应用为图像的每个7x7滑动块 IMG 。
请注意，名称 img 在这里重载：它是包含图像的变量的名称，它是<$ c $参数的名称c>有趣。

nlfilter is passed the function handle fun and can call it. In fact, it will apply fun with the parameter img as each 7x7 sliding block of the image img. Note that the name img is overloaded here: it is name name of a variable holding an image, and it is the name of the parameter of fun.

参见 function_handle（@）

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