Re: California License Plate font issues with OCR

Tue, 10 Aug 2010 10:01:32 -0700 

Dear Zia:
Leptonica can be easily integrated with Tesseract. As a matter of fact the new version of Tesseract will use Leptonica for layout analysis. Actually I'm on holiday (on a sailing boat around Sardinia island), I'm unable to answer you, but I will give you all technical details when I will return to my office on September 2°, As a starting point the subdirectory prog of the Leptonicadownload contains a lot of examples, I learn there, 
Giuseppe

--------------------------------------------------
From: "ZIA" <[email protected]>
Sent: Thursday, August 05, 2010 8:26 PM
To: "tesseract-ocr" <[email protected]>
Subject: Re: California License Plate font issues with OCR


Hello Giuseppe

I never heard about Leptonica, I am going to read about it and see how
it will help in my case. I went through your sample code, be honest,
it didn't make a lot of sense, I think should read about leptonica
first and then it will make sense. Just few question, as you said that
you are using this to locate the box contour. So,  can you explain
what is *seed_sequence value are and what it represent (dimension of
the box of medicine or what). I will read more about it and then I
will ask you more, but once again thanks for giving me something that
may work.

regards,
Zia

On Aug 2, 3:47 am, "Giuseppe Menga" <[email protected]> wrote:

Dear Zia,
I may give you a different idea for recovering the plate rectangle that
worked for me.
In my case I had to recover the box contour of a medicine in order to detect 
the expiration date in it.
I'm using Leptonica for this:
  static const char *seed_sequence = "o3.3 + r11 + o10.1 + c15.10 + x4";
  Pix* pix; // the input gray picture
  Pix  *pixm,*pixM; //the minima and maxima loci
  //int w,h;
  //pixGetDimensions(pix,&w,&h,NULL);
  pixLocalExtrema(pix,0,0,&pixm,&pixM); // to get minima and maxima
Pix *pixMd2 = pixMorphSequence(pixM, seed_sequence, 0); // some cleaning 
with opening and closing
  float skewAngle,conf;
Pix* pixMdd = pixFindSkewAndDeskew(pixMd2,1,&skewAngle,&conf); // deskew 
  // find baselines
  PTA* pta;
NUMA* numa = pixFindBaselines(pixMdd,&pta,0); // find the horizontal lines 
/*numa is an array of ordinates, pta is an array of points (x,y) - the
extreme points of  the horizontal  lines found for  each  ordinate. */
Extraxting with a simple logic the key four points ( or just three) of the 
main rectangle I build the clipping box.
Among different techniques this was the one more reliable, as the search for 
maxima is fairly insensitive to flares and reflections.
Let me know.
Giuseppe

----- Original Message -----
From: "ZIA" <[email protected]>
To: "tesseract-ocr" <[email protected]>
Sent: Monday, August 02, 2010 2:13 AM
Subject: Re: California License Plate font issues with OCR

Thanks Andre for finding the font. I will see how can i use that. As
you suggested using coreldraw, i don't have this software, i will try
to see if i can use some other software like MS word.

I was asking how to extract license plate from image. What I am doing,
i get the image, re-sized, convert to binary image and then run the
sobel edge filter. So now i have an image that shows me the rectangle
part of LP clearly, and I know the ration of height to width is 1 to
2. I just need to scan the image and look for rectangle and calculate
their ration, to get the correct LP from image, or is there any other
more efficient way. I hope this clear things, if not, I will send you
the image as input image and after edge filter image.

Zia

On Jul 31, 9:10 pm, Andres <[email protected]> wrote:
> > Anyway, any of you have any idea, about scanning image and getting > > the > >> LP (image was filtered using edge filter, i can see the rectangle > >> box 
> >> of LP, just need to figure out, how to scan and how to extract. The
> >> ratio of CA LP is 1 to 2, or 6 to 12 inches (height=6, width=12)
> >> I'm not sure about being understanding completelly. Could you extend > >> a 

> little ?

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