Convert from PIL Image and Numpy array to PyPNG format By Tim Sheerman-Chase, 2013 This code is released as CC0 and public domain code. Do what you will!

gistfile1.py

#Convert from PIL Image and Numpy array to PyPNG format
#By Tim Sheerman-Chase, 2013
#This code is released as CC0 and public domain code. Do what you will!

import png
from PIL import Image
import numpy as np

class NumpyArrayToPyPngAdapter:
	def __init__(self, img):
		self.img = img

	def __len__(self):
		return len(self.img)

	def __getitem__(self, key):
		row = self.img[key]
		out = []
		for p in row:
			if hasattr(p, '__iter__'):
				#Multi-channel image
				out.extend(p)
			else:
				#Single channel image
				out.append(p)
		return out

class PilImageToPyPngAdapter:
	def __init__(self, im):
		self.im = im
		self.iml = im.load()

	def __len__(self):
		return self.im.size[1]

	def __getitem__(self, row):
		out = []
		for col in range(self.im.size[0]):
			px = self.iml[col, row]
			if hasattr(px, '__iter__'):
				#Multi-channel image
				out.extend(px)
			else:
				#Single channel image
				out.append(px)
		return out

def PyPngToPilImage(width, height, rows, args):
	m = 'RGB'
	planes = int(args['planes'])
	if planes == 1: m = 'L'
	if planes == 4: m = 'RGBA'
	im = Image.new(m, (width, height))
	iml = im.load()
	for rowNum, row in enumerate(rows):
		for colNum in range(width):
			if planes > 1:
				iml[colNum, rowNum] = tuple(row[colNum*planes:(colNum+1)*planes])
			else:
				iml[colNum, rowNum] = row[colNum]
	return im

if __name__ == "__main__":
	im = Image.open("input.jpg")
	im = im.convert("RGB") # Single channel "L" should also work
	ima = np.array(im)

	fi = open("test.png","wb")
	wri = png.Writer(size=im.size, greyscale=(len(im.mode)==1))
	wri.write(fi, NumpyArrayToPyPngAdapter(ima))
	#wri.write(fi, PilImageToPyPngAdapter(im))
	fi.flush()

	read = png.Reader(file=open("test.png","rb"))
	readRet = read.read()
	print readRet
	pilim = PyPngToPilImage(*readRet)
	pilim.show()