How to crop license plate image automatically?

1.How to crop the attached license plate image automatically? 2.And using these coordinates how to draw red rectangle around license plate in original image?

Answer 1

[Image Analyst]

Get the bounding box with regionprops. Put up rectangle with rectangle. Crop with imcrop().

binaryImage = maskedImage > 0;
labeledImage = bwlabel(binaryImage);
measurements = regionprops(labeledImage, 'BoundingBox');
bb = [measurements.BoundingBox];
% Put up red rectangle
hold on;
rectangle('Position', bb, 'EdgeColor', 'r');
% Crop
croppedImage = imcrop(maskedImage, bb);

[NS]

Thanks! it worked. Now how to remove unnecessary things from background to get only letter and numbers?

[Image Analyst]

Try this: http://www.mathworks.com/help/vision/ref/ocr.html#bt548t1-2_1

[NS]

above link is for OCR. i have to first remove unnecessary parts to get image with only letters. like i want LEE8368 in the image. then i use OCR for recognition.

[Image Analyst]

For some arbitrarily-shaped blob, how do you know if it's a letter or not unless you check if it's a letter or not? That's why I suggested OCR. I haven't used it so I can't really be sure what it will say if it tries to evaluate a blob that's not a letter or number shape. Do you? Maybe it will say "this blob is not a letter or number" - if so, you're all set.

[NS]

Ok. I'll try. Thanks.

[mae magdadaro]

what is the output of this code?

binaryImage = maskedImage > 0; labeledImage = bwlabel(binaryImage); measurements = regionprops(labeledImage, 'BoundingBox'); bb = [measurements.BoundingBox]; % Put up red rectangle hold on; rectangle('Position', bb, 'EdgeColor', 'r'); % Crop croppedImage = imcrop(maskedImage, bb);

[Image Analyst]

It looks like the cropped image, croppedImage, is the output.