#!/usr/bin/env ruby
require 'rubygems'
require 'rmagick'
require 'pp'

###
# Converts a gif file to c code to enable displaying animations.
#
# The data format is described in animations.h
###

DEBUG = true

def compress(data, use_cutoff=true)
	cutoff = 3
	escape = 255
	last = data[0]
	result = []
	count = 0
	data.each do |x|
		if x == last
			count += 1
		end

		if x!=last || count==255
			if use_cutoff
				if count <= cutoff
					count.times { result << last }
				else
					result << escape << count << last
				end
			else
				result << count << last
			end
			count = 1
			last = x
		end
	end
	if use_cutoff
		if count < cutoff
			count.times { result << last }
		else
			result << escape << count << last
		end
	else
		result << count << last
	end
	return result
end

unless ARGV[0]
	puts "Usage:"
	puts "#{$0} <gif_file> [OPTIONS]"
	puts "e.g. '#{$0} mario.gif'"
	puts
	puts "OPTIONS:"
	puts "  --full-frames         Don't use optimiziation; output each frame as full frame."
	puts
	puts "Resulting data format is described in animations.h"
	exit 1
end

image_file=ARGV[0]
full_frames = ARGV.include?("--full-frames")
name=File.basename(image_file, File.extname(image_file))
frames = Magick::ImageList.new(image_file)

STDERR.puts "Found #{frames.count} frames."

ticks_per_second = frames.ticks_per_second

total_x, total_y = frames.first.columns, frames.first.rows

STDERR.print "Getting colors..."
colors = []
frames.each do |frame|
	if frame.columns!=total_x || frame.rows!=total_y
		raise "The gif file has frames with different sizes. Such gifs are not supported at the moment, sorry."
	end
	frame.columns.times do |x|
		frame.rows.times do |y|
			color = frame.pixel_color(x, y).to_color(Magick::AllCompliance, true, 8, true)[1,8].to_i(16)
			colors << color
		end
	end
end
colors = colors.uniq

STDERR.puts " Found #{colors.count} colors."

transparent = colors.select{|c| c & 0xFF == 0}

STDERR.puts "#{transparent.count} color(s) being transparent."

# color[0] is "keep the color from the previous frame"
# color[1] is "background color"
colors = ([0x00000012, 0x00000013] + (colors - transparent)).uniq
STDERR.puts "Using #{colors.count} colors."
raise "Number of colors has to be 255 or less!" if colors.count>255

STDERR.puts

p_frame = nil
frames_data = []
times = []

frames.each_with_index do |frame, index|
	data = []
	if index==0 # first frame
		frame.rows.times do |y|
			frame.columns.times do |x|
				color = frame.pixel_color(x, y).to_color(Magick::AllCompliance, true, 8, true)[1,8].to_i(16)
				if transparent.include? color
					data << 1
				else
					data << colors.index(color)
				end
			end
		end
	else
		frame.rows.times do |y|
			frame.columns.times do |x|
				color = frame.pixel_color(x, y).to_color(Magick::AllCompliance, true, 8, true)[1,8].to_i(16)
				p_color = p_frame.pixel_color(x, y).to_color(Magick::AllCompliance, true, 8, true)[1,8].to_i(16)

				if color==p_color && !full_frames
					data << 0
				elsif transparent.include? color
					data << 1
				else
					data << colors.index(color)
				end
			end
		end
	end
	time = (1000.0 / ticks_per_second * frame.delay).round
	if frame==0 || data.uniq!=[0]
		times << time
		frames_data << data
	else
		old_time = times.pop
		times << old_time + time
	end
	p_frame = frame

	if DEBUG
		STDERR.puts "Frame ##{index}:"
		total_y.times do |y|
			total_x.times do |x|
				STDERR.print data[x + y*total_x]==0 ? "." : "X"
			end
			STDERR.puts
		end
	end
end

data = frames_data.map{|d| compress(d, true)}

s=0
d = "PIA\x01__" +
	[total_x, total_y].pack("C*") +
	[frames_data.count, colors.count-2].pack("C*") +
	colors[2..-1].map{|c| [c>>24 & 0xFF, c>>16 & 0xFF, c>>8 & 0xFF]}.flatten.pack("C*") +
	times.pack("n*") +
	(data.map{|d| d.count}).pack("n*") +
	data.flatten.pack("C*")
	
dd = "PIA\x01__" +
	"XY:" + [total_x, total_y].pack("C*") +
	"FC,CC:" + [frames_data.count, colors.count-2].pack("C*") +
	"COLORS:" + colors[2..-1].map{|c| [c>>24 & 0xFF, c>>16 & 0xFF, c>>8 & 0xFF]}.flatten.pack("C*") +
	"TIME:" + times.pack("n*") +
	"LENGTHS:" + (data.map{|d| d.count}).pack("n*") +
	"DATA:" + data.flatten.pack("C*")

size = d.length
d[4] = (size >> 8 & 0xFF).chr
d[5] = (size & 0xFF).chr

STDERR.puts
STDERR.puts "Space usage:"
STDERR.puts "  Colors:      %6d bytes." % [s1=(colors.count-2) * 3] # colors are 3-bytes, but we have to use uint32_t, which takes up 4 bytes.
STDERR.puts "  Data:        %6d bytes." % [s2=data.flatten.count]
STDERR.puts "  Delays:      %6d bytes." % [s5=times.count * 2 + 1]
STDERR.puts "  Offsets:     %6d bytes." % [s3=data.count * 2]
STDERR.puts "  TOTAL:       %6d bytes." % [s1+s2+s3+s5]
STDERR.puts "  REALLY:      %6d bytes." % d.size
STDERR.puts "Original size: %6d bytes." % [s4=File.new(image_file).size]
STDERR.puts "Difference:    %6d bytes." % [s1+s2+s3+s5 - s4]
STDERR.puts

# File format
# Bytes 0-2: P I A (magic number)
# Byte  3: Version (currently 1)
# Bytes 4-5: Total file size
# Byte  6: width
# Byte  7: height
# Byte  8: frame_count
# Byte  9: color_count

# Color data, 3*color_count bytes
# Frame times, 2*frame_count bytes
# frame offsets, 2*frame_count bytes

STDERR.puts "Writing data to #{name}.pia..."
File.new("#{name}.pia", "w").write(d)
File.new("#{name}.pia.debug", "w").write(dd)