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Overview:
========
Giftrans Porting - Darkness Patch: patch for the Giftrans tool.
The patch implements a new option in the Giftrans software.
The option can be used to decrease the colors brightness of the image according to the darkness index (option parameter).

Author:
======
Carmine Benedetto

Website: http://www.carminebenedetto.net
Email: carmine.benedetto[at]gmail.com


Patch Description:
=================
The patch modify each entry of the RGB Global Color Table and of the RGB Local Color table using the following rules:

- GLOBAL COLOR TABLE
	gct[RED] = gct[RED] / (2 * dark_v);		
	gct[GREEN] = gct[GREEN] / (2 * dark_v);
	gct[BLUE] = gct[BLUE] / (2 * dark_v);

- LOCAL COLOR TABLE
	buffer[RED] = buffer[RED] / (2 * dark_v);
	buffer[GREEN] = buffer[GREEN] / (2 * dark_v);
	buffer[BLUE] = buffer[BLUE] / (2 * dark_v);

The 'dark_v' variable depends on the darkness option parameter.


New Option Sintax:
=================
-d darkness_index

Possible values for 'darkness_index': 0 - black and white image, 1, 2 or 3.
The higher the 'darkness_index' chosen, the higher the image darkness level.


Usage:
=====
./giftrans -d <index_parameter> <input_file> -o <output_file>


Usage Examples:
==============
./giftrans -d 0 image.gif -o p0.gif
./giftrans -d 1 image.gif -o p1.gif
./giftrans -d 2 image.gif -o p2.gif
./giftrans -d 3 image.gif -o p3.gif


Tests:
=====
The directory test/ contains some operating tests.


Command used to generate the patch file:
=======================================
diff -aNur giftrans.c.orig giftrans.c > patch-dk

- a , treats it as text;
- N , treats absent files as empty;
- u , output as unified;
- r , recursively.


Command used to add the patch to the original code:
==================================================
patch < patch-dk
patch gitrans.c.origin patch-dk


Note about some Giftrans Errors:
===============================
The Giftrans software to work needs a the "rgb.txt" file.
If this file is missing on your Operating System, you can find it in the utils/ directory.

See the following Giftrans code section to find out where to copy the "rgb.txt" file:

#define X11             /* When using X Window System */
#undef  OPENWIN         /* When using Open Windows */
#undef  X386            /* When using XFree86 with FreeBSD/386BSD */
#undef  OS2             /* When using IBM C/C++ 2.0 */
#ifndef MSDOS           /* required for TurboC 1.0 */
#undef  MSDOS           /* When using Borland C (maybe MSC too) */
#endif

#ifndef OS2_OR_MSDOS
#ifdef OS2
#define OS2_OR_MSDOS
#endif /* OS2 */
#ifdef MSDOS
#define OS2_OR_MSDOS
#endif /* MSDOS */
#endif /* OS2_OR_MSDOS */

char copyright[] = "@(#)Copyright (C) 1994 by Andreas Ley (ley@rz.uni-karlsruhe.de)";
char sccsid[] = "@(#)GIFtrans v1.12.2 - Transpose GIF files";

#ifndef RGBTXT
#ifdef X11
#define RGBTXT  "/usr/lib/X11/rgb.txt"
#else /* X11 */
#ifdef OPENWIN
#define RGBTXT  "/usr/openwin/lib/rgb.txt"
#else /* OPENWIN */
#ifdef X386
#define RGBTXT  "/usr/X386/lib/X11/rgb.txt"
#else /* X386 */
#ifdef OS2_OR_MSDOS
#define RGBTXT  "rgb.txt"
#else /* OS2_OR_MSDOS */
#define RGBTXT  "";
#endif /* OS2_OR_MSDOS */
#endif /* X386 */
#endif /* OPENWIN */
#endif /* X11 */
#endif /* RGBTXT */