#! /usr/bin/perl -w
#
# $Id$
# Copyright (c) 2007 patrick keshishian <NO-SPAM@SPAM-PROTECT- - - -.com>

use strict;
use GD;

# global vars
my $self = `basename $0`;
chomp($self);

# proto-sub
sub main();

# main
main();
exit(0);

# subs
sub main()
{
	my ($wm_file, $src_file, $out_file);
	my ($iw, $is, $io);
	my $percent = 55.0; # transparency

	# set-up
	$wm_file = 'circ.png';
	$src_file = 'test_in.jpg';
	$out_file = sprintf('test_out_v1_%.1f.jpg', $percent);
	GD::Image->trueColor(1);

	# open source image
	$is = GD::Image->new($src_file) or
	    die(sprintf("Failed to open \"%s\"", $src_file));
	# open watermark image
	$iw = GD::Image->new($wm_file) or
	    die(sprintf("Failed to open \"%s\"", $wm_file));
	printf("iw->trueColor() = %d$/", $iw->trueColor());
	printf("is->trueColor() = %d$/", $is->trueColor());
	#
	# Copy watermark onto source image using GD::Image->copyMerge(),
	# similar to GD::Image->copy() but with one extra argument specifying
	# extent to which the colours of the two images are to be merged.
	# At first sight, this function is misleading, giving one the (or
	# at least to me) that GD would do proper alpha-blending.
	# Not so.  The actually comment for the GD's C library function,
	# gdImageCopyMerge() reads:
	#
	# /* This function is a substitute for real alpha channel operations,
	#    so it doesn't pay attention to the alpha channel. */
	#
	$is->copyMerge($iw, 50, 50, 0, 0, $iw->width, $iw->height, $percent);
	# open destination/out file for writing
	open(OUT, ">$out_file") or
	    die(sprintf("Failed to write \"%s\": %s", $out_file, $!));
	# write out resulting image
	print(OUT $is->jpeg(70));
	close(OUT);
	exit(0);
}