#!/usr/bin/python

import png
from sys import argv
from itertools import tee, izip

img = png.Reader(argv[1]).read()

def group(it, num):
    res = []
    for el in it:
        res.append(el)
        if len(res) == num:
            yield tuple(res)
            res = []

w = img[0]
h = img[1]
pic = img[2]
coef = [float(c) for c in argv[3:6]]
gamma = float(argv[6])

w = png.Writer(w, h, greyscale=True, alpha=True)

outpic = []

for line in pic:
    outline = []
    for x,y,z,a in group(line, 4):
        l = (coef[0]*x + coef[1]*y + coef[2]*z)/255.
        if not a:
            a = 255
        else:
            a = max(0, min(255, int(255*(1 - l**gamma))))
        outline += [255, a]
    outpic.append(outline)

with open(argv[2], 'w') as f:
    w.write(f, outpic)