how to make line and drawing line in image

i try to make line between column in an image..first step i must find in column 1,in row what the first black pixel,and in row what the last black pixel in column 1...step 2 after i found the coordinat, i try to find the average which is the formula : (pixel black first+pixel black last)/2..and i will find the value..and then i will looping this unto the end of column that i have...if the task finished, i try to connected coordinat 1-2-3-4 until the last pixel..is there anybody can help me ?

this is the code :

baca = imread('88.bmp');

% %%========================pre processing===============================

% %convert to binary

glurus4=im2double(baca);

cannyawal = im2bw(glurus4,graythresh(glurus4));

cannyawal=~cannyawal

% figure,imshow (bacabwlurus4), title ('Citra black and white dari tulisan

garis dasar lurus');

%%*************Edge Detection*************************

% cannyawal = edge (bacabwlurus4,'canny');

% figure,imshow (cannyawal), title ('Citra tulisan canny');

% %%******************

[baris kolom] = size(cannyawal);

for kolom1=1:kolom

    for baris1=1:baris

        if cannyawal(baris1,kolom1)==1     

          bataskanan=kolom1;

            end

    end

end

for kolom2=kolom:-1:1

    for baris2=1:baris

    if cannyawal(baris2,kolom2)==1

        batas_kiri=kolom2;

        end

    end

end

for baris3=1:baris

     for kolom3=1:kolom

          if cannyawal(baris3,kolom3)==1

              batas_bawah=baris3;

            end

        end

end

    for baris4=baris:-1:1

        for kolom4=1:kolom

            if cannyawal(baris4,kolom4)==1

                batas_atas=baris4;

            end

        end

    end

   height=((batas_bawah-batas_atas));

   width=((bataskanan-batas_kiri));

Gamcrop = imcrop(cannyawal,[batas_kiri batas_atas width height]);%%position

vector, [xmin ymin width height].

 figure,imshow (Gamcrop), title ('Citra setelah proses Crop');

GbrAkhir =imresize(Gamcrop,[50,20]);

[x y] = size(GbrAkhir) ;

for c=1:1:y

        for baris1=x:-1:1

        for kolom1=c

            if GbrAkhir(baris1,kolom1)==1

                pixel_1_awal=baris1;

            end

        end

    end

for baris2=1:x

     for kolom2=c

          if GbrAkhir(baris2,kolom2)==1

              pixel_1_akhir=baris2;

            end

        end

end

% pixel_1_awal

% pixel_1_akhir

rata_rata(c) = [pixel_1_akhir+pixel_1_awal]/2;

% m(rata_rata,:)=[x y]

z=ceil(rata_rata);

if GbrAkhir(baris1,kolom1)~=1

                pixel_1_awal=0;

            end

if GbrAkhir(baris2,kolom2)~=1

              pixel_1_akhir=0;

            end

        end

[r u] =size(z);

for i=1:u

     input_uji_88=z(1:1:i);

end

uu=[21,30,25,26,33,31,35,32,37,0,34,39,41,42,0,38,0,0,42,46;]

hold on

M = size(uu,1);

N = size(uu,2);

for k = 1:1:M

    xx = [1 N];

    yy = [k k];

    plot(xx,yy,'Color','w','LineStyle','-');

    plot(xx,yy,'Color','k','LineStyle',':');

end

for k = 1:1:N

    xx = [k k];

    yy = [1 M];

    plot(xx,yy,'Color','w','LineStyle','-');

    plot(xx,yy,'Color','k','LineStyle',':');

end

hold off

[Dwi Putra Alexander]

this is sample for image :

[IMG]http://i42.tinypic.com/2qi8nrb.jpg[/IMG]