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Date: Fri, 31 Aug 2012 01:58:04 -0700 (PDT)
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Subject: Re: Question: re Image Files.
From: Austin Obyrne <austin.obyrne@hotmail.com>
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Date: 2012-08-31T01:58:04-07:00
List-Id: <comp.lang.ada>

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 pi=
xels in a similar arithmetical way. Yes, but you have to handle each indivi=
dual 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, o=
r look at what you are really doing and see if ther is not a way to general=
ise. > If not how are image files handled in Ada is there any transformatio=
n 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 retu=
rns 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 thi=
s here: http://people.freebsd.org/~markm/raw_io.adb (Disclaimer: I've not b=
een using Ada for long; this program is likely not particularly idiomatic u=
se 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=20
<the structure of the files, and simply reading them byte-by-byte. That=20
<way you get a stream of numbers, all in the range 0-255, and as long=20
<as the decryption process returns the numbers to exactly what the=20
<original number was without missing or adding any, you can encrypt any=20
<file you like.=20

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 l=
ink ?

Many thanks - adacrypt