pngcompress

#!/usr/bin/env python

import sys, os, math
from PIL import Image


def usage():
	print ("Usage:")
	print ("\tcompress input_file out_image")
	print ("\tcompress -d image out_file")

if len(sys.argv) == 1:
	usage()
	exit(0)

if(sys.argv[1] == '-d'):
	operation = 'decompress'
	idx = 1
else:
	operation = 'compress'
	idx = 0

if len(sys.argv) < (idx + 3):
	usage()
	exit(0)

inFile = sys.argv[idx + 1]
outFile = sys.argv[idx + 2]

if not os.path.exists(inFile):
	print ("input file does not exist")
	exit()

def encodeDataRGB(str, outFile):
	print("length of input file: %s" % len(str))

	size = int ( math.ceil( math.sqrt(len(str) / 3) ) )
	#size = int( math.ceil( math.sqrt(len(str)) )) + 1
	#print("width of picture = %s, number of pixels = %s" % (size, size * size))
	print("width of picture = %s, number of pixels = %s, number of bytes = %s" % (size, size * size, size * size * 3))

	im = Image.new("RGB", ( size, size ), (0x00))

	ending = len(str) % 3
	datalen = len(str) + (3 - ending)
	if(ending > 0):
		str = str + chr(0xFF) + chr(0x00)*(3-ending - 1)

	data = [];
	for i in range(int( datalen / 3)):
		idx = i * 3
		byte = (ord(str[idx]), ord(str[idx+1]), ord(str[idx+2]))
		data.append(byte)

	data.append((0xFF,0xFF,0xFF)); #we set last byte to 0xFF to mark the end of data

	im.putdata(data)
	im.save(outFile)

def encodeDataGrayScale(str, outFile):
	print("length of input file: %s" % len(str))

	#size = math.ceil( math.sqrt(len(str) / 3) )
	size = int( math.ceil( math.sqrt(len(str)) )) + 1
	print("width of picture = %s, number of pixels = %s" % (size, size * size))
	#print("width of picture = %s, number of pixels = %s, number of bytes = %s" % (size, size * size, size * size * 3))

	im = Image.new("L", ( size, size ), (0x00))

	data = [];
	for i in range(len(str)):
		byte = ord(str[i])
		data.append(byte)

	data.append(0xFF); #we set last byte to 0xFF to mark the end of data

	im.putdata(data)
	im.save(outFile)

def decodeDataGrayScale(inFile, outFile):
	if not os.path.exists(inFile):
		print("File %s was not found" % inFile)
		exit()

	im = Image.open(inFile)
	data = list(im.getdata())
	dataLen = len(data)
	outStr = ""
	
	for offset in range(1, len(data)):
		if data[-offset] == 0xFF:
			dataLen -= offset
			break

	for px in range(dataLen):
		outStr += chr(data[px])

	f = open(outFile, 'w+')
	f.write(outStr)


if operation == 'compress':
	input = open(inFile, 'r')
	encodeDataGrayScale( input.read(), outFile )
else:
	decodeDataGrayScale( inFile, outFile )