#!/bin/sh

# gifcap: Make an iFunny GIF caption
# Copyright (C) 2024 Sasha Koshka (pseudonymous)
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

name="$0"
font="Futura Condensed Extra Bold"
input=""
output=""
caption=""

usage () {
	echo "Usage: $name [OPTION]... CAPTION..."
	echo "Make an iFunny GIF caption."
	echo ""
	echo "  -f, --font        specify a font to use (default: ifunny.otf)"
	echo "  -i, --input       the input file (required)"
	echo "  -o, --output      the output file (default: input)"
	echo "      --help        display this help and exit"
}

while test $# -gt 0; do
	case $1 in
	-f|--font)
		font="$2"
		shift; shift
		;;
	-i|--input)
		input="$2"
		shift; shift
		;;
	-o|--output)
		output="$2"
		shift; shift
		;;
	--help)
		usage
		exit 0
		;;
	-*|--*)
		usage
		exit 2
		;;
	*)
		if test -z "$caption";
		then caption="$1"
		else caption="$caption $1"
		fi
		shift
		;;
	esac
done

if test -z "$input"; then
	usage
	exit 2
fi

if test -z "$output"; then
	output="captioned-`basename "$input"`"
fi

if ! test -f "$input"; then
	echo "$name: $input not found"
	exit 1
fi

captionWidth="512x"
captionTemp=`mktemp --suffix=".png"`
imageWidth=`convert "$input" -format "%[w]x" info:`

echo "$name: generating caption..."
convert \
	-background white -fill "#010000" -font "$font" \
	-pointsize 55 -size "$captionWidth" -gravity Center \
	caption:"$caption" \
	-bordercolor white -border 20x20 \
	"$captionTemp"

echo "$name: compositing over $input..."
# https://www.imagemagick.org/discourse-server/viewtopic.php?t=33797
convert \
	"$captionTemp" -resize "$imageWidth" \
	-background white \( "$input" -coalesce \) \
	-set page "%[fx:u.w]x%[fx:u.h+v.h]+%[fx:t?(u.w-v.w)/2:0]+%[fx:t?u.h:0]" -coalesce \
	null: -insert 1 -layers composite -layers optimize \
	"$output"

rm "$captionTemp"
echo "$name: done!"