#!/usr/bin/perl 

#*************************************************************************
# This program uses Linux GIMP to cut out smaller pieces from a large
# image, adjust the transfer curve and save as a JPEG with choosable
# quality. Output files get numbered sequentially with given base,
# starting with 0, increasing by column, top left to lower right.
# Program needs to be called as
#
# crop_and_save.pl IPATH OUTPRE XSIZE YSIZE XN YN XOOFF YOOFF IOFF JOFF XOFF YOFF QUAL TRANS
#
# with 
# IPATH, input file
# OUTPRE, output filename prefix
# XSIZE, size in x of output files
# YSIZE, size in y of output files
# XN, number of images to be clipped in x
# YN, number of images to be clipped in y
# XOOFF, naming numbering offset in x (first image has number XOOFF+YOOFF*XN, I think...; this is JUST numbering)
# YOOFF, naming numbering offset in y
# IOFF, starting not at i=0 but ioff (real skipping of some area while keeping numbering)
# JOFF, starting not at j=0 but joff
# XOFF, skipping xoff pixel off top  (skipping this much pixels)
# YOFF, skipping yoff pixel off left
# QUAL, JPEG saving quality, 0.0 to 1.0 (80% should be good)
# TRANS, name of transfer curve
#
# Transfer curve maps input brightness value to output brightness value
# -lin: linear (no change)
# -lin30: linear but setting 30 (of 256) lowest values to black
# -lin50: as above but lowest 50 values
# define any other curve as a 256 value array with transfer values
# from 0th to 255 brightness level
#
# Author: Knud Jahnke, 
# Astrophysikalisches Institut Potsdam
# http://www.aip.de/~jahnke/
#
# Version 1.0, March 2004
#
# Bugs: 
#    -absolutely no error handling, it just dies the ugly way...
#    -crashes when accessing pixels beyond image borders
#*************************************************************************

use Getopt::Std;
getopts('f:');
# **** Activate Gimp usage ***********
use Gimp;
# ************************************
my @args=();
if($opt_f){
    open(FI,"<$opt_f") or die "invalid file\n";
    @args=<FI>;
    close(FI);
    for my $l (@args){chomp($l);$l=~ s/\s*\#.*$//}
}else{
my $nn=$#ARGV;
if($nn<=13){
print "Call with \n\t\"$0 ipath outpre xsize ysize xn yn xooff yooff ioff joff xoff yoff qual trans\"\nor\t $0 -f <file>\n ";
exit(0);
}
# **** Read command line input *******
@args=@ARGV;
}
my ($ipath, $outpre, $xsize, $ysize, $xn, $yn, $xooff, $yooff, $ioff, $joff, $xoff, $yoff, $qual, $trans) = @args;

if (! -e $ipath){
print "No vaild input-graphics found \n";
exit(0);
}
# ************************************
# **** Define transfer curves ********
# Linear
my @lin;
for ($i=0;$i<256;$i++) {$lin[$i] = $i;};

# Linear but set to 0 from 0--50
my @clip50 = @lin;
my $zerolim = 50;
for ($i=0;$i<$zerolim;$i++) {
    $clip50[$i] = 0;
}
$clip50[0] = 1;

# Linear but set to 0 from 0--30
my @clip30 = @lin;
$zerolim = 30;
for ($i=0;$i<$zerolim;$i++) {
    $clip30[$i] = 0;
}
$clip30[1] = 1;
# ************************************

# **** Start a Gimp session **********
Gimp::init;
# ************************************


# **** deciding on transfer curve ****
if ($trans eq "clip30") {
    @transcurve = @clip30;
} elsif ($trans eq "clip50") {
    @transcurve = @clip50;
} else {
    @transcurve = @lin;
}
# ************************************

# **** Load image ********************
my $img_tile = Gimp->file_load ($ipath, $ipath);
# ************************************


#**** loop over a tile ****
for ($i=$ioff;$i<$xn;$i++) {
    for ($j=$joff;$j<$yn;$j++) {
	$joff=0;
	#opening is time consuming, save a copy of image in memory
	my $img = Gimp::gimp_channel_ops_duplicate($img_tile);
        #define cropping offsets and image name
	my $xclipoff = $i*$xsize+$xoff;
	my $yclipoff = $j*$ysize+$yoff;
	my $iman = ($i+$xooff)*($yn+$yooff) + $j + $yooff;
	my $oname = $outpre . $iman . '.jpg';

	#Say something to the user about progress
	print "Xclipoff = ", $xclipoff, ",\tYclipoff = ", $yclipoff, ",\tIma #", $iman, "\n";
	# crop
	Gimp->gimp_crop($img,$xsize,$ysize,$xclipoff,$yclipoff);
	my $layer = ($img->get_layers)[0]; #get first layer	
	
	# Changing background
        Gimp::gimp_curves_explicit($layer, 0, 256, \@transcurve);
	
	
        # Save image
        Gimp::file_jpeg_save(1, $img, $layer, $oname, $oname, $qual, 0, 1, 0, 'have a nice day!', 1, 1, 0, 1);
	
        # Delete working image copy from memory to free space
	$img->delete;
    }
}
#Delete also other copy and exit
$img_tile->delete;