Question: re Image Files.

Question: re Image Files.

[Austin Obyrne]

Question:

In Ada I can use the Ada Package “WITH Ada.Text_IO” to read in a character from ASCII and operate on it like so,

InChar      : Character;
InCharValue : Integer ;

Then,

Ada.Text_IO. Get (Item => Inchar);
InCharValue :=  Character ‘POS (Inchar);

I can then operate on InCharValue mathematically.

Question: Is there any way by which I can reading in from an image file and operate on the individual pixels in a similar arithmetical way.

If not how are image files handled in Ada is there any transformation process?.

Your help would be greatly appreciated.

 - adacrypt

Re: Question: re Image Files.

[Adam Beneschan]

On Thursday, August 30, 2012 3:33:34 PM UTC-7, Austin Obyrne wrote:
> Question:
> 
> 
> Question: Is there any way by which I can reading in from an image file and operate on the individual pixels in a similar arithmetical way.
> 
> If not how are image files handled in Ada is there any transformation process?.

You might want to check out "Generic Image Decoder":
 
http://sourceforge.net/projects/gen-img-dec/?source=directory

but I haven't looked into it, so I have no idea if it will do what you need.

                          -- Adam

Question: re Image Files.

[tmoran]

>Question: Is there any way by which I can reading in from an image file and
> operate on the individual pixels in a similar arithmetical way.

There are lots of different formats of image files.  Claw has packages
for Windows' internal, and external (bmp), formats.  You get an array with
8 1 bit pixels/byte if it's a monochrome image up to 4 bytes/pixel if it
has 2**24 color bits and an alpha channel (like a Javascript HTML5 canvas
image).  There are lots of other packages available to read/write jpg,
tga, etc file formats.  It's a whole wide world - what do you want to do?

Re: Question: re Image Files.

[Dmitry A. Kazakov]

On Thu, 30 Aug 2012 15:33:34 -0700 (PDT), in comp.lang.ada you wrote:

> Question: Is there any way by which I can reading in from an image file
> and operate on the individual pixels in a similar arithmetical way.
> 
> If not how are image files handled in Ada is there any transformation process?.

The issue of presentation already answered. As for arithmetical ways that
depends on the color model assuming that pixel represents a color space
point. There are various models L*a*b, RGB, HLS, HSV, IHLS. Mathematical
operations over color space points, e.g. "darken", "+", "average," are
implemented within these models slightly or very differently.

P.S. Ada has bindings to major graphical frameworks (Qt, GTK, Win32 GDI).

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

Re: Question: re Image Files.

[Mark Murray]

On 30/08/2012 23:33, Austin Obyrne wrote:
 > Question: Is there any way by which I can reading in from an image 
file and operate on the individual pixels in a similar arithmetical way.

Yes, but you have to handle each individual image format (GIF, JPEG,
BMP etc) separately. This is a LOT of work to write a general program.
Either pick one type that you are going to use, or look at what you
are really doing and see if ther is not a way to generalise.

 > If not how are image files handled in Ada is there any transformation 
process?

Would I be correct in guessing that you are planning in reading these
files with the intention of encrypting the contents?

If so, then you can save yourself a MASSIVE amount of work by ignoring
the structure of the files, and simply reading them byte-by-byte. That
way you get a stream of numbers, all in the range 0-255, and as long
as the decryption process returns the numbers to exactly what the
original number was without missing or adding any, you can encrypt any
file you like.

There is demo code to do this here:
http://people.freebsd.org/~markm/raw_io.adb

(Disclaimer: I've not been using Ada for long; this program is likely
not particularly idiomatic use of the language; suggestions for 
improvement gratefully accepted).

M
-- 
Mark "No Nickname" Murray
Notable nebbish, extreme generalist.

Re: Question: re Image Files.

[Brian Drummond]

On Thu, 30 Aug 2012 15:33:34 -0700, Austin Obyrne wrote:

> ... how are image files handled in Ada is there any transformation
> process?.
> 
> Your help would be greatly appreciated.
> 

See also
http://gen-img-dec.sourceforge.net/

- Brian

Re: Question: re Image Files.

[Austin Obyrne]

On Friday, August 31, 2012 8:18:11 AM UTC+1, Mark Murray wrote:
> On 30/08/2012 23:33, Austin Obyrne wrote: > Question: Is there any way by which I can reading in from an image file and operate on the individual pixels in a similar arithmetical way. Yes, but you have to handle each individual image format (GIF, JPEG, BMP etc) separately. This is a LOT of work to write a general program. Either pick one type that you are going to use, or look at what you are really doing and see if ther is not a way to generalise. > If not how are image files handled in Ada is there any transformation process? Would I be correct in guessing that you are planning in reading these files with the intention of encrypting the contents? If so, then you can save yourself a MASSIVE amount of work by ignoring the structure of the files, and simply reading them byte-by-byte. That way you get a stream of numbers, all in the range 0-255, and as long as the decryption process returns the numbers to exactly what the original number was without missing or adding any, you can encrypt any file you like. There is demo code to do this here: http://people.freebsd.org/~markm/raw_io.adb (Disclaimer: I've not been using Ada for long; this program is likely not particularly idiomatic use of the language; suggestions for improvement gratefully accepted). M -- Mark "No Nickname" Murray Notable nebbish, extreme generalist.

<If so, then you can save yourself a MASSIVE amount of work by ignoring 
<the structure of the files, and simply reading them byte-by-byte. That 
<way you get a stream of numbers, all in the range 0-255, and as long 
<as the decryption process returns the numbers to exactly what the 
<original number was without missing or adding any, you can encrypt any 
<file you like. 

That is precisely what I want to do - I have no other interest in the image file apart from using the alpha + pixels dat as the operands of encryption transformations.

Can I do explicitly and print out the bytes as they are read in with this link ?

Many thanks - adacrypt

Re: Question: re Image Files.

[Austin Obyrne]

On Friday, August 31, 2012 8:18:11 AM UTC+1, Mark Murray wrote:
> On 30/08/2012 23:33, Austin Obyrne wrote: > Question: Is there any way by which I can reading in from an image file and operate on the individual pixels in a similar arithmetical way. Yes, but you have to handle each individual image format (GIF, JPEG, BMP etc) separately. This is a LOT of work to write a general program. Either pick one type that you are going to use, or look at what you are really doing and see if ther is not a way to generalise. > If not how are image files handled in Ada is there any transformation process? Would I be correct in guessing that you are planning in reading these files with the intention of encrypting the contents? If so, then you can save yourself a MASSIVE amount of work by ignoring the structure of the files, and simply reading them byte-by-byte. That way you get a stream of numbers, all in the range 0-255, and as long as the decryption process returns the numbers to exactly what the original number was without missing or adding any, you can encrypt any file you like. There is demo code to do this here: http://people.freebsd.org/~markm/raw_io.adb (Disclaimer: I've not been using Ada for long; this program is likely not particularly idiomatic use of the language; suggestions for improvement gratefully accepted). M -- Mark "No Nickname" Murray Notable nebbish, extreme generalist.

I have compiled your program and I get an error meassge -"random is undefined" -perhaps you could save me the trouble of going through all your sorce code to determine how I should declare it.

Can I say 

random: Integer; -- ok or not

- adacrypt

Re: Question: re Image Files.

[Ludovic Brenta]

Austin Obyrne wrote on comp.lang.ada:
> That is precisely what I want to do - I have no other interest in
> the image file apart from using the alpha + pixels dat as the
> operands of encryption transformations.

So, you want an attacker of your encryption scheme to know that the
cleartext is an image? And to know the structure of the image file
format?  That doesn't sound like encryption to me.  Proper
encryption should not only obscure the contents but also, and most
importantly, the structure of the cleartext.  All current encryption
methods make an explicit effort to be agnostic about the structure
of whatever it is they encrypt.  For example, disk partitions can
be encrypted at the disk block level -- even directories, file
names and permissions can be encrypted just like everything else,
to give attackers a really hard time extracting any meaningful data
from an encrypted disk.

-- 
Ludovic Brenta.

Re: Question: re Image Files.

[Dmitry A. Kazakov]

On Fri, 31 Aug 2012 02:25:18 -0700 (PDT), Ludovic Brenta wrote:

> Austin Obyrne wrote on comp.lang.ada:
>> That is precisely what I want to do - I have no other interest in
>> the image file apart from using the alpha + pixels dat as the
>> operands of encryption transformations.
> 
> So, you want an attacker of your encryption scheme to know that the
> cleartext is an image?

To transmit messages undetected hidden within innocently looking images?
Usual scheme is to slightly manipulate channels.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

Re: Question: re Image Files.

[Mark Murray]

On 31/08/2012 10:14, Austin Obyrne wrote:
> Can I say
>
> random: Integer; -- ok or not

No. Just remove the "Shuffle" function; it isn't used. You also won't
need the "Block" type definition.

Please attempt to answer this sort of question by experimentation
and by examining the code; finding that "Shuffle" was not used and
can therefore be ignored would have been a helpful exercise in reading
and understanding the code.

M
-- 
Mark "No Nickname" Murray
Notable nebbish, extreme generalist.

Re: Question: re Image Files.

[Austin Obyrne]

On Friday, August 31, 2012 6:09:39 PM UTC+1, Mark Murray wrote:
> On 31/08/2012 10:14, Austin Obyrne wrote: > Can I say > > random: Integer; -- ok or not No. Just remove the "Shuffle" function; it isn't used. You also won't need the "Block" type definition. Please attempt to answer this sort of question by experimentation and by examining the code; finding that "Shuffle" was not used and can therefore be ignored would have been a helpful exercise in reading and understanding the code. M -- Mark "No Nickname" Murray Notable nebbish, extreme generalist.

That program is a disgrace - I have checked out the concept also and it does nothing for the problem - it is a mis application - you're not in that league that you can hand out rebukes and admonitions - you are deluding yourself - any body else who has checked your link wil agree - and to find it doesn't even complile properly on top of it all should surely make you cringe. LOL

Why don't you post a demonstartion here of a sample program that works.

I shouldn't have bothered listening to you knowing your past but I was being considerate to a foolish degree given your unfortunate record.

Yes put up a demo her for all to see.

- adacrypt

Re: Question: re Image Files.

[gautier_niouzes]

Le vendredi 31 août 2012 09:18:11 UTC+2, Mark Murray a écrit :

> Yes, but you have to handle each individual image format (GIF, JPEG,
> BMP etc) separately. This is a LOT of work to write a general program.

Sure. The good news is that it is already done :-)
Download or check-out GID: http://gen-img-dec.sf.net/ 
Then all the work is to define a container, say a flat byte buffer or a two-dimensional array, then define 2 procedures, e.g. here for a flat buffer:

    procedure Set_X_Y (x, y: Natural) is
    begin
      idx:= 3 * (x + image_width * (image_height - 1 - y));
    end Set_X_Y;
    --
    procedure Put_Pixel (
      red, green, blue : Primary_color_range;
      alpha            : Primary_color_range
    )
    is
    begin
      buffer(idx..idx+2):= (red, green, blue);
      idx:= idx + 3;
    end Put_Pixel;

plus a feedback procedure that can be null (just there for showing progess), then instanciate a procedure:

    procedure Load_image is
      new GID.Load_image_contents(
        Primary_color_range, 
        Set_X_Y,
        Put_Pixel, 
        Feedback, 
        GID.fast
      );

An that's it! PNG, BMP, GIF, JPEG, TGA are auto-detected.
You don't need to tell GID under what format the image is encoded.
I guess Austin is trying to do steganography.
The simplest way it to take test\mini.adb and customize it for that purpose.
Have fun!
_________________________ 
Gautier's Ada programming 
http://freecode.com/users/gdemont

Re: Question: re Image Files.

[Shark8]

Here's one for you then. It builds a shuffled array over the given type, which can be used to index into something like a deck of cards or somesuch.

Generic
    Type Element is (<>);
    Low  : Natural:= Element'Pos(Element'First);
    High : Natural:= Element'Pos(Element'Last);
Package Random is
    SubType Element_Range is Integer Range Low..High;
    Function Incrementor Return Element;
    Type Element_Array is Array(Element_Range) of Element;

    Values : Element_Array;
    Procedure Print;
End Random;

--------------------------

With
	Ada.Text_IO,
	Ada.Numerics.Discrete_Random;

Use
	Ada.Text_IO;

Package Body Random is
    Count : Element := Element'First;

    Function To_Integer( Input : in Element ) Return Element_Range is
    begin
	Return Low;
    end;
    
    
    Function Incrementor Return Element is
    begin
	Return Result : Element:= Count do
	    Null;
	    Count:= Element'Succ( Result );
	Exception
	    When Constraint_Error => Count:= Element'First;
	End Return;
    end Incrementor;

    Procedure Swap( Index_1, Index_2 : In Integer ) is
	Temp : Constant Element:= Values( Integer(Index_1) );
    begin
	Values( Integer(Index_1) ):= Values( Integer(Index_2) );
	Values( Integer(Index_2) ):= Temp;
    end Swap;

    Procedure Print is
    begin
	Put_Line( "Length: " & Values'Length'Img );
	Put( "(" );
	For Index in Values'First..Integer'Pred(Values'Last) loop
	    Put( Values(Index)'Img & ',' );
	end loop;
	Put( Values(Values'Last)'Img );
	Put_Line( ")" );
    end Print;


Begin
    null;
    Shuffle:
    Declare
	Package Random_Element is New
	  Ada.Numerics.Discrete_Random( Element_Range );
	Number : Random_Element.Generator;
	Use Random_Element;
	Function Random( Gen : Generator ) Return Element_Range
		 Renames Random_Element.Random;
    Begin
	Reset( Number );
	Values:= Element_Array'( Others => Incrementor );
	       For Index in Element_Array'Range loop
	          Swap( Index, Random(Number) );
	       end loop;
    End Shuffle;
End Random;

Re: Question: re Image Files.

[Austin Obyrne]

On Friday, August 31, 2012 10:12:59 PM UTC+1, (unknown) wrote:
> Le vendredi 31 août 2012 09:18:11 UTC+2, Mark Murray a écrit : > Yes, but you have to handle each individual image format (GIF, JPEG, > BMP etc) separately. This is a LOT of work to write a general program. Sure. The good news is that it is already done :-) Download or check-out GID: http://gen-img-dec.sf.net/ Then all the work is to define a container, say a flat byte buffer or a two-dimensional array, then define 2 procedures, e.g. here for a flat buffer: procedure Set_X_Y (x, y: Natural) is begin idx:= 3 * (x + image_width * (image_height - 1 - y)); end Set_X_Y; -- procedure Put_Pixel ( red, green, blue : Primary_color_range; alpha : Primary_color_range ) is begin buffer(idx..idx+2):= (red, green, blue); idx:= idx + 3; end Put_Pixel; plus a feedback procedure that can be null (just there for showing progess), then instanciate a procedure: procedure Load_image is new GID.Load_image_contents( Primary_color_range, Set_X_Y, Put_Pixel, Feedback, GID.fast ); An that's it! PNG, BMP, GIF, JPEG, TGA are auto-detected. You don't need to tell GID under what format the image is encoded. I guess Austin is trying to do steganography. The simplest way it to take test\mini.adb and customize it for that purpose. Have fun! _________________________ Gautier's Ada programming http://freecode.com/users/gdemont

Many thanks for your coding of the “Generic Image Decoder “ for my benefit.
- that was really appreciated - Austin

Re: Question: re Image Files.

[Anatoly Chernyshev]

> Would I be correct in guessing that you are planning in reading these
> 
> files with the intention of encrypting the contents?
> 
> If so, then you can save yourself a MASSIVE amount of work by ignoring
> 
> the structure of the files, and simply reading them byte-by-byte. That
> 
> way you get a stream of numbers, all in the range 0-255, and as long
> 
> as the decryption process returns the numbers to exactly what the
> 
> original number was without missing or adding any, you can encrypt any
> 
> file you like.

This way the image data will be lost, because the headers will be screwed as well. Apparently Austin is trying to play with the pixels only (e.g. for steganography purposes or whatever).

When I had similar problem I've chosen PNG format as input (because the IO library was immediately available at http://sourceforge.net/projects/png-io). For the output I had to write my own package for uncompressed 24 bpp BMPs (because the format is simple). Then PNG is converted into an integer matrix, which could be manipulated any way you like, and then written at any time as BMP (which could later be converted by any graphic editor to other formats if needed).

If interested, I put relevant files in www.achernyshev.com/tmp/bmp24bppout.rar

Re: Question: re Image Files.

[Mark Murray]

On 03/09/2012 07:02, Anatoly Chernyshev wrote:
> This way the image data will be lost, because the headers will be screwed as well. Apparently Austin is trying to play with the pixels only (e.g. for steganography purposes or whatever).

He's trying to play with the pixels only because he doesn't understand
file structure in general. If he can't see it, he dismisses it, so the
metainformation is not considered. Why he's now fixated on images is
anyone's guess; mine is that its a lame attempt to encrypt binary files
(see below).

Simply put, if he can't see it, he doesn't understand it, so when
encrypting plainTEXT he encrypts only ASCII (printable subset), thus
wrecking the file structure by losing newlines, tabs etc.

Its been explained to him many times before, but he just doesn't
"get" that he needs to encrypt 8-bit bytes while ignoring file
structure.

M
-- 
Mark "No Nickname" Murray
Notable nebbish, extreme generalist.

Re: Question: re Image Files.

[Antti Louko]

On 2012-08-31 20:36, Austin Obyrne wrote:

> That program is a disgrace - I have checked out the concept also and
> it does nothing for the problem - it is a mis application - you're
> not in that league that you can hand out rebukes and admonitions -
> you are deluding yourself - any body else who has checked your link
> wil agree - and to find it doesn't even complile properly on top of
> it all should surely make you cringe. LOL
>
> Why don't you post a demonstartion here of a sample program that
> works.
>
> I shouldn't have bothered listening to you knowing your past but I
> was being considerate to a foolish degree given your unfortunate
> record.

Austin Obyrne, you are a disgrace yourself.  Mark offers you a program
what does _exactly_ what you request, reading and writing raw files,
reading to integer values in range 0..255 and and writing them back to
file.  Applying this information in your crypto program would give you
_exactly_ the functionality you are looking for: a general file
encryption and decryption.

Instead of thanking him, you insult him.  His program, after removing
the suffle procedure, compiles and works. To get it run in speed in
Linux, one would of course replace /dev/random with /dev/urandom, but
that is also a detail any competent programmer would notice. And you
using Windows wouldn't even notice as in Windows you would need to
replace that with something else.

Austin Obyrne, you are a moron, go away and leave us alone.