Re: [Libexif-devel] Question about JPG file access and ExifHeader access

[Benny S. <ich...@pa...>]

Dan,

I looked at the example "cam_features.c" and realized that there is another
library "libjpeg" with files that contain the file-access functions.

This is tricky for me because I am not using libexif on a high-level system
and so I cannot do an install of the whole exif functionality, as the
library assumes.

I have to tailor the libraries to fit the embedded platform on which I am
working (Rabbit Semiconductor core modules).

I have finally converted all of the libexif library files over to Rabbit's
Dynamic C environment.  Now, I will need to convert the libjpeg library as
well.

Since the compact flash card I am using is full of digital-camera JPG files,
it is formatted and partitioned with FAT16.  Rabbit Dynamic C has a whole
set of file access functions dedicated to FAT file systems.  So, I must
convert all of the fwrite), fread(), fopen(), etc. calls in the libjpeg
files over to Dynamic C FAT-file parlance.  I assume that such concerns are
transparent in a high-level application of libexif since the operating
system would know that the CF card is FAT-enabled and take care of such
things, right?

Back to the memory issue (not an issue in high-level applications on a PC,
etc.), are the libjpeg library functions reading/writing an entire JPG file?
This matters because the Rabbit core module I selected only has 128K of RAM.
I figured that would be enough for a complete Exif header (64K bytes), but
JPG files are bigger than 128K.  This could be a deal-breaker for the Rabbit
module I have chosen.  Maybe for the entire Rabbit platform.

I keep dreaming of finding someone who has done all this before in an
embedded environment and can just hand me the keys.

Whew!

Benny

-----Original Message-----
From: Dan Fandrich [mailto:da...@co...] 
Sent: Tuesday, December 30, 2008 2:06 PM
To: lib...@li...
Subject: Re: [Libexif-devel] Question about JPG file access and ExifHeader
access

> Also, I am trying to understand how libexif will know about and be able to
> write to/read from the memory on my microcontroller module ((I have 128K
of
> RAM available).

Did you want more specific information than you got a few weeks ago?
libexif
uses memory on both the stack and heap, using the standard C allocation
methods..

>>> Dan
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