Jpegpixi - JPEG pixel interpolator
==================================


What is it?
-----------

"Jpegpixi" is short for "JPEG pixel interpolator". The intent of the program
is to interpolate pixels in JFIF images (commonly referred to as "JPEG
images"). This is useful to correct images from a digital camera with CCD
defects. For example, if one pixel is always bright green, this pixel can be
interpolated away with jpegpixi.

Jpegpixi is unique in that it tries to preserve the quality of the JFIF
image as much as possible. Usual graphics programs decode JFIF images when
they are loaded, and re-encode them when they are saved, which results in an
overall loss of quality. Jpegpixi, on the other hand, does not decode and
re-encode the image, but manipulates the encoded image data (known as the
"discrete cosine transformation coefficients"). Therefore, the blocks
(typically 8x8, 8x16, or 16x16 pixel areas) which contain the pixels to be
interpolated are minimally disturbed, and other blocks remain pixel-by-pixel
identical to the original image.

Jpegpixi is a command line utility. It is Free Software, released under the
GNU General Public License (GPL). The full text of the GPL is contained in
the file `COPYING'.

This software is based in part on the work of the Independent JPEG Group.
See `README.jpeglib' for copyright and license information.


Installation
------------

The file `INSTALL' contains general installation instructions. If you have not
yet read it, please do so now.

To build jpegpixi, you must have the JPEG library by the Independent JPEG Group
(version 6b or later) installed. It can be downloaded from
<ftp://ftp.uu.net/graphics/jpeg/jpegsrc.v6b.tar.gz>.

You can specify the location of the JPEG library when you run the `configure'
script with the option `--with-jpeglib' or the options `--with-jpeglib-include'
and `--with-jpeglib-lib'. Please type `./configure --help' for more information.

The files `optpixi.c' and `optpixi.h' are built from `jpegpixi.opag', and the
files `opthotp.c' and `opthotp.h' are built from `jpeghotp.opag', with `opag',
a command line option parser generator. If you want to modify `jpegpixi.opag'
or `jpeghotp.opag', but don't have `opag' installed, you can download it from
<http://www.zero-based.org/software/opag/>. Version 0.7.0 or later is required.
You can also specify the location of the `opag' executable when you run the
`configure' script with the option `--with-opag'. Please type `./configure
--help' for more information.


Usage
-----

Please read the manual page for detailed instructions. For a usage example,
please see the "Example" section on the jpegpixi homepage at
<http://www.zero-based.org/software/jpegpixi/>.
