straighten the jagged boundary and how to count lenght of boundary.

I want to find the edge of a line image, but If i detect with canny and sobel, thats not suitable, not straight but the problem is the line still irregular lines,,, I NEED M-FILE CODING : How to straighten out the jagged lines on the edges and calculate the length of the edge :

my problem : <http://tinypic.com/view.php?pic=33oglzp&s=6>

link picture 1 : <http://tinypic.com/view.php?pic=k4yyyd&s=6>

link picture 1 : <http://tinypic.com/view.php?pic=zumsjm&s=6>

[Ryan]

You have had more than enough help and examples given to you by this point that you should be able to figure out this out. Just find the perimeter, locate the corners and then calculate the distance between the corners.

Answer 1

[Image Analyst]

I'm not sure I understand why you don't have this yet. I gave you a snippet of code that uses imtransform() to warp an image to make it rectangular. All you had to do was to find the corners, and I think I gave you hints for that.

For that matter, I'm not even sure why you need to do this at all when the problem could be completely avoided by having your camera directly overhead from your tile and a jig to ensure precise positioning of tile samples in the field of view. Why go through all this bother when you don't have to?

As far as the jaggies go, don't worry about them. You don't need to "straighten them out" - you just don't. Why do you think you do?

You could use regionprops() on the transformed image and calculate the length of the perimeter that way, or use bwboundaries() and use the Pythagorean theorem. I think the outer perimeter length would only vary if the tile were chipped or broken.

[KURNIAWAN]

yeah,, thanks before image analyst, ur code about imtransform to warp an image,, but how to plot that code automaticly the corner of tile,,, because in my experiment will use interface later, so need automatic without tag the corner one by one, can u give code m-file how tag automaticallly the corner of tile and directly know the cordinate of edge corner..

i use this code ( to count the lenght of edge,, but the line of edge still jaggies , i think its not accurately in value of lenght edge with jagges line,,

_________________________________________

[B,L] = bwboundaries(bw,'holes');

% Display the label matrix and draw each boundary

imshow(label2rgb(L, @jet, [.1 .1 .1]))

hold on

for k = 1:length(B)

boundary = B{k};

plot(boundary(:,2), boundary(:,1), 'w', 'LineWidth', 2)

end

%deklarasi variable

stats = regionprops(L,'Area','Perimeter', 'MajorAxisLength' )

jml_panjang = 0

panjang_terpanjang = 0

panjang_terpendek = 0

%Perhitungan

for k = 1:length(B)

boundary = B{k};

delta_sq = diff(boundary).^2;

perimeter =sum(sqrt(sum(delta_sq,2)));

area = stats(k).Area;

metric = 4*pi*area/perimeter^2;

if metric < 0.75 && area >300

panjang = stats(k).MajorAxisLength;

text(boundary(1,2)-35, boundary(1,1)+35, sprintf('%2.2f', panjang),'Color','y', 'Fontsize',12, 'FontWeight','bold');

jml_panjang = jml_panjang

if panjang_terpanjang < panjang

panjang_terpanjang = panjang

end

if panjang_terpendek <= 0

panjang_terpendek = panjang

end

if panjang_terpendek > panjang

panjang_terpendek = panjang

end

end

end

_________________________________________________

and the result picture still have jaggies on edge, i think count the lenght not acurrately,, my picture after bwboundaries become this : <http://tinypic.com/view.php?pic=15chlpk&s=6>

please help me,,

[Image Analyst]

That's why it's called DIGITAL image analysis. That happens everywhere in the computer world because that's what happens if you quantize/digitize data. If you don't want to sum the length of the pixels in the line, then just find the endpoint locations and use the Pythagorean theorem.

[KURNIAWAN]

yah ,, the point one that i dont know,, how to find coordinat pixel ofcorner tile automatically ,, can u help me in code m-file please

[Walter Roberson]

http://www.mathworks.com/help/toolbox/vision/ref/cornerdetection.html

http://www.mathworks.com/matlabcentral/fileexchange/7652

[KURNIAWAN]

thanks walter roberson,, but im still confuse,, after we detect the corner and next how to know the location pixel of corner,, thats fileexchange that u gave before about detect the timing to detect corner,, but i need detect the corner and fine coordinate of corner,, can u help me

[Walter Roberson]

The source code for #7652 is in a .rar file, so I cannot look at it. I see nothing in the documentation that would suggest that "timing" is being examined.

[Image Analyst]

Maybe you could try the corner() function in the Image Processing Toolbox.

[Walter Roberson]

Ah, that function is newer than the release I normally run.

[KURNIAWAN]

hemm??? im confuse,, pls help

[Walter Roberson]

At the MATLAB command prompt, command

help corner

If it gives you help information then you can use that corner-finding routine to find the corners in your image.