first4.m

利用sobel算子和霍夫变换求出图像的边缘

%=======================================first4.m========================================
%i1~i4,j1~j4表示霍夫数组中前四大数的坐标
i1=1;
j1=1;
i2=1;
j2=1;
i3=1;
j3=1;
L = size(H);

%查找前四大的数据
for i = 1:L(1),
    for j = 1:L(2),
        if H(i,j)>H(i1,j1),
            i4 = i3;
            j4 = j3;
            i3 = i2;
            j3 = j2;
            i2 = i1;
            j2 = j1;
            i1 = i;
            j1 = j;
        end
    end
end

%求得四条直线的参数
th1 = pi*(j1 - 1)/(Nmax - 1)/2;
th2 = pi*(j2 - 1)/(Nmax - 1)/2;
th3 = pi*(j3 - 1)/(Nmax - 1)/2;
th4 = pi*(j4 - 1)/(Nmax - 1)/2;
r1 = 3000*(i1 -1)/(Mmax - 1);
r2 = 3000*(i2 -1)/(Mmax - 1);
r3 = 3000*(i3 -1)/(Mmax - 1);
r4 = 3000*(i4 -1)/(Mmax - 1);

%绘制4条直线
x = 1:2274;
y1 = round((r1 - x*cos(th1))/sin(th1));
y2 = round((r2 - x*cos(th2))/sin(th2));
y3 = round((r3 - x*cos(th3))/sin(th3));
y4 = round((r4 - x*cos(th4))/sin(th4));
plot(x,y1,x,y2,x,y3,x,y4);
%=====================================first4.m(end)=====================================