PNG manipulation module in Python 2/3

imagescripter.py

import png # pip install pypng

class pixel:
    def __init__(self, x=0, y=0, r=0, g=0, b=0, a=0):
        self.x = x
        self.y = y
        self.r = r
        self.g = g
        self.b = b
        self.a = a
    def clone(self, r=None, g=None, b=None, a=None):
        return pixel(self.x, self.y, self.r if r is None else r, self.g if g is None else g, self.b if b is None else b, self.a if a is None else a)

class image_scripter:
    progress = 0.0
    # Create a scripter from a file name or file object
    def __init__(self, file):
        self._image_in = png.Reader(file)
        self.width, self.height, data, self.metadata = self._image_in.read()
        self._image_in_data = []
        self._image_out_data = None
        y = 0
        for row in data:
            self._image_in_data.insert(y, [] * (self.width * self.metadata["planes"]))
            for x in range(0, self.width * self.metadata["planes"], self.metadata["planes"]):
                self._image_in_data[y].insert(int(x/self.metadata["planes"]), pixel(int(x/self.metadata["planes"]), y, row[x], row[x+1] if self.metadata["planes"] > 1 else 0, row[x+2] if self.metadata["planes"] > 2 else 0, row[x+3] if self.metadata["planes"] > 3 else 0))
            y+=1
    
    # Returns a pixel at a location
    def get(self, x, y):
        return self._image_in_data[y][x]

    # Sets a pixel
    def set(self, px):
        self._image_in_data[px.y][px.x] = px
    
    # Operates on the image using a function
    # Any previous output will cycle to input
    # Prototype: func(scripter, pixel)
    def operate(self, func):
        if self._image_out_data != None:
            self._image_in_data = self._image_out_data
        self._image_out_data = []
        for i in range(0, self.height): self._image_out_data.insert(i, [] * (self.width * self.metadata["planes"]))
        i = 0
        for row in self._image_in_data:
            for px in row:
                self.progress = i / (self.width * self.height)
                self._image_out_data[px.y].insert(px.x, func(self, px))
                i+=1
        self.progress = 1.0
    
    # Writes the output to a file
    def write(self, file):
        img = png.Writer(self.width, self.height, size=self.metadata["size"], greyscale=self.metadata["greyscale"], alpha=self.metadata["alpha"], planes=self.metadata["planes"], bitdepth=self.metadata["bitdepth"], interlace=self.metadata["interlace"], gamma=self.metadata["gamma"])
        rows = []
        for i in range(0, self.height): rows.insert(i, [0] * (self.width * self.metadata["planes"]))
        y=0
        for r in self._image_out_data:
            x=0
            for px in r:
                rows[y][x*self.metadata["planes"]] = px.r
                if self.metadata["planes"] > 1: rows[y][x*self.metadata["planes"]+1] = px.g
                if self.metadata["planes"] > 2: rows[y][x*self.metadata["planes"]+2] = px.b
                if self.metadata["planes"] > 3: rows[y][x*self.metadata["planes"]+3] = px.a
                x+=1
            y+=1
        fp = open(file, "wb")
        img.write(fp, rows)
        fp.close()

# Opens an image, operates on it, and writes the output to a file
def run(input, func, output):
    scripter = image_scripter(input)
    scripter.operate(func)
    scripter.write(output)

z_example.py

# Turns image grayscale and flips it upside down
import imagescripter
def test(scripter, pixel):
    p = scripter.get(pixel.x, scripter.height - pixel.y - 1)
    avg = int((p.r + p.g + p.b) / 3)
    return p.clone(avg, avg, avg)
imagescripter.run("input.png", test, "output.png")