License Plate Recognition - need help to improve code.. :)

Hello everybody. At start sorry for my English..:P I have code for LPR:

I = imread('tablice\4.jpg'); 

BW = im2bw(I,0.4); 

% figure;imshow(BW) 

se = strel('rectangle', [2 20]); 
BW_opened = imclose(BW,se); 
figure, imshow(BW_opened,[]) 

s=regionprops(BW_opened,'Area','BoundingBox'); 
[~,ii] = sort([s.Area],'descend'); 
out = imcrop(I,s(ii(2)).BoundingBox); 
figure 
imshow(out);

At this photo:

https://dl.dropbox.com/u/19214852/7.jpg

After compilation i have output image:

https://dl.dropbox.com/u/19214852/output.jpg

I want to have an output image of same license plate- with no other parts of car body and background.. If someone can help me and will improve my code ? I will be very grateful.

Regards

Michal

Answer 1

[Image Analyst]

That algorithm you have is way to simple to be of any real world use. But we don't do major algorithm development here. Look at section 16.7.2.5 on "License Plate Recognition, Extraction, Analysis" in Vision Bib to see how people do it successfully.

Answer 2

[Matt Kindig]

Hi Michal,

You might have more luck thresholding the three color planes (red, green, and blue) separately, rather than thresholding all three planes to the same level (0.4 in your code). I found some luck with this approach:

I = imread('https://dl.dropbox.com/u/19214852/7.jpg');
r = I(:,:,1);  %red plane 
g = I(:,:,2);  %green plane
b = I(:,:,3);  %blue plane
BW = (r >= 230) & (r <= 260) & (g >= 160) & (g <= 240) & (b >= 160) & (b <= 240);
s = regionprops(BW, 'Area', 'BoundingBox');
[~, ii] = sort([s.Area], 'descend');
out = imcrop(I, s(ii(1)).BoundingBox);
imshow(out);