Help with Mathematica: Transforming Image Pixels to Natural Numbers

[Andreanne]

Hi, I am trying to do a transformation on an image with the program Mathematica in the same way stated in the following scientific article :
http://arxiv.org/PS_cache/arxiv/pdf/0710/0710.0021v1.pdf
I would like to associate each pixel of the picture with a pair of natural numbers. I used the command Flatten and created a set of all the pixels of the image, then I don't know what else to do...

 

[Bill Simpson]

Do you have any experience programming in Delphi so you can understand some of his 5 page program in the article?

Do you have any experience programming in Mathematica so you can implement simple things?

If you are lacking one or both of those skills then you might want to look for simple programming tutorials in the language you lack.

I don't see an obvious block of code which seems to be this-is-where-a-byte-is-encrypted. There is lots of fooling around with buttons and input and output, but I can't identify a tiny part of that which does the encryption that you could try to port to Mathematica. Perhaps someone else can see where that is.

 

[Andreanne]

I have no experience programming in Delphi, in Mathematica I can only program simple things.

Thank you for your help.

 

[Bill Simpson]

I suggest you find a nice introduction to Delphi, preferably a well written book. Learn enough about that to enable you to understand most of the statements in his five pages of Delphi code in his paper. You perhaps don't need to learn enough to be able to write programs in Delphi, just enough so you can understand programs someone else has written and gotten to run.

At the same time I suggest you try to understand enough about his non-code parts of the paper to roughly understand his encryption method.

While doing that perhaps you can sort through his code and see if you can identify and isolate a small part of the code that encrypts a single number or perhaps a single row of numbers.

If you can see how to separate all the stuff he has for buttons and input and output and I assume windows and other things like that then perhaps there may be only a page, or possibly even less, of code that actually encrypts a number. I'm always a fan of starting with the smallest possible task when doing something new. Can you correctly encrypt a single number? That would be an excellent start. I don't recall if he has a concrete example of encrypting a single number or a small row. If he has that then what you want to do is to be able to get exactly the same result he does. If he doesn't have that then (DO NOT tell him I sent you) try to contact the author and explain that you are just getting started and trying to understand and implement his code in a new language and you would really REALLY like to have an extremely simple first test case to verify your work. Perhaps if he is nice he will send you a paragraph of explanation and an unencrypted and encrypted list of numbers. That will be gold for you to use. Be REALLY polite when you contact this person and see if he will be nice to you.

Once you think you have simplified things down to just encrypting one number or one row and you can translate his Delphi into simple pseudocode the post another message with what you have done and what you don't understand and where you are stuck. Someone might be nice enough to provide you with hints then.

 

[alphy]

I would suggest using the "ImageData" function in Mathematica to extract the pixel values of the image. This will give you a matrix of numbers representing the color values of each pixel. From there, you can use the "Flatten" command to convert the matrix into a list of numbers. To associate each pixel with a pair of natural numbers, you can use the "MapIndexed" function to apply a function to each element in the list, where the function takes the position of the element in the list (which can be converted to a pair of natural numbers) as an argument. This will give you a list of pairs of natural numbers corresponding to each pixel in the image. I hope this helps in your transformation process.