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# Image Comparison

On Programmer » Matlab

2,164 words with 0 Comments; publish: Mon, 28 Apr 2008 21:19:00 GMT; (200125.00, « »)

morrido <dr_morrido.matlab.todaysummary.com.hotmail.com> wrote in message

<27051782.1196203950106.JavaMail.jakarta.matlab.todaysummary.com.nitrogen.mathforum.

org>...

> I have extracted the numbers of a sudoku puzzle, i have a

number in each image..

> this image is the smallest crop possible of the number..

> Now I want to compare theses images (each containing a

number) with the images with numbers stored in a database..

> the thing is.. due to several transformations crucial to

obtaining the numbers from the sudoku puzzle..

> the images i extracted from the sudoku puzzle are

different from the ones in the database by 1 border pixel

or so...

> how can i compare the image i extracted with one in the

database when they have different sizes?

> thnx in advance =)

Here is an answer to a problem you didn't actually ask.

Suppose you image your complete Sudoko grid, complete will

all its numbers. Now take your database images of the

individual numbers (making sure that the digits themselves

are of comparable size to digits imaged from the grid), and

zero pad them to be the same size as the image of your

complete grid, Fourier transform these, and store the

transformed images in another database.

On getting the image of your Sudoko grid, Fourier transform

it, then take the first transformed digit reference matrix,

and do a 'pixel' by 'pixel' multiplication of both

transformed images. Applying the inverse Fourier transform

to the product should - if all is well - generate a grid

size image with bright spots corresponding to squares

occupied by that reference digit. Going through all of the

transformed digits in this way will allow you to generate a

set of bright spots which will allow you to identify the

layout of the original grid.

Probably no use to you what so ever, but you can't win them

all.

Regards

Dave Robinson

*http://matlab.todaysummary.com/q_matlab_30098.html*

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