POV-Ray : Newsgroups : povray.programming : Targa format specifics Server Time
28 Mar 2024 18:23:13 EDT (-0400)
  Targa format specifics (Message 1 to 3 of 3)  
From: Anthony D  Baye
Subject: Targa format specifics
Date: 30 May 2009 15:55:00
Message: <web.4a218df39d8a58d2231d6f4b0@news.povray.org>
I understand that POV does not use color-mapped images of any format, but I am
working on a program that reads targa files, and the information I've found
regarding the pseudo-color format is descriptively vague in places.  I'm hoping
that someone here can remedy my ignorance.

The documentation for the Truevision targa format states that color map indices
are stored in the image data as an integral number of bytes - usually one or
two - but does not say how to tell if it's one or two.  Seeing as how the
images can have depths up to 32 bit, I could see the index values approaching
four bytes but, again, there's no indication of how big I should expect the
index values to be.

Then too, the Targa format tends to put two byte values in little-endian form,
or maybe it places all numeric values in little-endian form, but this
information, which I would think important, is simply left out of every piece
of documentation I have found to date.

If anyone can help me with this problem, I'd be grateful.

A.D.B.


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From: Christian Froeschlin
Subject: Re: Targa format specifics
Date: 30 May 2009 19:05:11
Message: <4a21bba7$1@news.povray.org>
> I understand that POV does not use color-mapped images of any format

actually you can read them into an image_map just fine ;)

> The documentation for the Truevision targa format states that color map indices
> are stored in the image data as an integral number of bytes - usually one or
> two - but does not say how to tell if it's one or two.

It seems to be unclear on this point, but my guess would be that
the size is the same for all pixels and depends solely on the color
map length (if number of colors <= 256 then 1 byte else ...).

> Then too, the Targa format tends to put two byte values in little-endian form,
> or maybe it places all numeric values in little-endian form, but this
> information, which I would think important, is simply left out of every piece
> of documentation I have found to date.

I didn't work with TGA before but Google turned up

   http://www.martinreddy.net/gfx/2d/TGA.txt

where it says "The low-order byte of a two-byte field is
stored first" under Image Data Field.


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From: DungBeatle
Subject: Re: Targa format specifics
Date: 2 Oct 2009 18:46:02
Message: <4ac682aa$1@news.povray.org>
Found this:

http://en.wikipedia.org/wiki/Truevision_TGA
http://www.organicbit.com/closecombat/formats/tga.html
http://tfcduke.developpez.com/tutoriel/format/tga/fichiers/tga_specs.pdf

Some source code:
http://local.wasp.uwa.edu.au/~pbourke/dataformats/tga/tgatest.c

I have a pretty book on Graphics File Formats and if you
can't find what you need here, I'll scan the pages in over
the weekend...




"Anthony D. Baye" <Sha### [at] spamnomorehotmailcom>
wrote in message
news:web.4a218df39d8a58d2231d6f4b0@news.povray.org...
> I understand that POV does not use color-mapped images of
any format, but I am
> working on a program that reads targa files, and the
information I've found
> regarding the pseudo-color format is descriptively vague
in places.  I'm hoping
> that someone here can remedy my ignorance.
>
> The documentation for the Truevision targa format states
that color map indices
> are stored in the image data as an integral number of
bytes - usually one or
> two - but does not say how to tell if it's one or two.
Seeing as how the
> images can have depths up to 32 bit, I could see the index
values approaching
> four bytes but, again, there's no indication of how big I
should expect the
> index values to be.
>
> Then too, the Targa format tends to put two byte values in
little-endian form,
> or maybe it places all numeric values in little-endian
form, but this
> information, which I would think important, is simply left
out of every piece
> of documentation I have found to date.
>
> If anyone can help me with this problem, I'd be grateful.
>
> A.D.B.
>
>


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