2. Create the functions:

png2graymatrix(filename) - creates and returns a 'Matrix' object with the image data returned by file2image() from the module 'image'; 'filename' is a string data type specifying the location of the image you wish to use. If the image is not grayscale, you must convert it to grayscale prior to creating the 'Matrix' object. You can do so using the functions isgray() and color2gray(), also found in the 'image' module.

graymatrix2png(image_matrix, path) - creates a png file out of a 'Matrix' object. You may want to use the function image2file() from the 'image' module.

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import image def png2graymatrix(filename): """a single line of code should go here""" if """the image is not gray""": image_data = """get image data""" return """Matrix object"""

def graymatrix2png(img_matrix, path): """two lines of code go here"""

"""------------------TESTER FOR FUNCTIONS png2graymatrix() AND graymatrix2png()-------------------------""" M = png2graymatrix("male12.png") # matrix for male12.png F = png2graymatrix("female00.png") # matrix for female00.png C = M * 0.5 + F * 0.5 # convex combo: each image contributes half their instensity

graymatrix2png(C, "mixedfaces.png") # converting the matrix to png named mixedfaces

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image.py:

""" Basic types: file - a png file on disk image - a list of list of pixels. pixels can be triples of RGB intensities, or single grayscale values. display - not a type per se, but rather causing the type to be shown on screen

Functions convert between these formats, and also can write to temporary files and display them with a web browser. """

# To do: check types of arguments, check that image has no alpha channel # Note that right now, we ignore the alpha channel, but allow it. - @dbp

import png import numbers import collections

# Native imports import webbrowser import tempfile import os import atexit

# Round color coordinate to nearest int and clamp to [0, 255] def _color_int(col): return max(min(round(col), 255), 0)

# utility conversions, between boxed pixel and flat pixel formats # the png library uses flat, we use boxed. def _boxed2flat(row): return [_color_int(x) for box in row for x in box]

def _flat2boxed(row): # Note we skip every 4th element, thus eliminating the alpha channel return [tuple(row[i:i+3]) for i in range(0, len(row), 4)]

## Image conversions def isgray(image): "tests whether the image is grayscale" col = image[0][0] if isinstance(col, numbers.Number): return True elif isinstance(col, collections.Iterable) and len(col) == 3: return False else: raise TypeError('Unrecognized image type')

def color2gray(image): """ Converts a color image to grayscale """ # we use HDTV grayscale conversion as per https://en.wikipedia.org/wiki/Grayscale image = [[x for x in row] for row in image] return [[int(0.2126*p[0] + 0.7152*p[1] + 0.0722*p[2]) for p in row] for row in image]

def gray2color(image): """ Converts a grayscale image to color """ return [[(p,p,p) for p in row] for row in image]

#extracting and combining color channels def rgbsplit(image): """ Converts an RGB image to a 3-element list of grayscale images, one for each color channel""" return [[[pixel[i] for pixel in row] for row in image] for i in (0,1,2)]

def rgpsplice(R,G,B): return [[(R[row][col],G[row][col],B[row][col]) for col in range(len(R[0]))] for row in range(len(R))]

## To and from files def file2image(path): """ Reads an image into a list of lists of pixel values (tuples with three values). This is a color image. """ (w, h, p, m) = png.Reader(filename = path).asRGBA() # force RGB and alpha return [_flat2boxed(r) for r in p]

def image2file(image, path): """ Writes an image in list of lists format to a file. Will work with either color or grayscale. """ if isgray(image): img = gray2color(image) else: img = image with open(path, 'wb') as f: png.Writer(width=len(image[0]), height=len(image)).write(f, [_boxed2flat(r) for r in img])

## Display functions def image2display(image, browser=None): """ Stores an image in a temporary location and displays it on screen using a web browser. """ path = _create_temp('.png') image2file(image, path) hpath = _create_temp('.html') with open(hpath, 'w') as h: h.writelines(["

" % path]) openinbrowser('file://%s' % hpath, browser) print("Hit Enter once the image is displayed.... ", end="") input()

_browser = None

def setbrowser(browser=None): """ Registers the given browser and saves it as the module default. This is used to control which browser is used to display the plot. The argument should be a value that can be passed to webbrowser.get() to obtain a browser. If no argument is given, the default is reset to the system default.

webbrowser provides some predefined browser names, including: 'firefox' 'opera'

If the browser string contains '%s', it is interpreted as a literal browser command line. The URL will be substituted for '%s' in the command. For example: 'google-chrome %s' 'cmd "start iexplore.exe %s"'

See the webbrowser documentation for more detailed information.

Note: Safari does not reliably work with the webbrowser module, so we recommend using a different browser. """ global _browser if browser is None: _browser = None # Use system default else: webbrowser.register(browser, None, webbrowser.get(browser)) _browser = browser

def getbrowser(): """ Returns the module's default browser """ return _browser

def openinbrowser(url, browser=None): if browser is None: browser = _browser webbrowser.get(browser).open(url)

# Create a temporary file that will be removed at exit # Returns a path to the file def _create_temp(suffix='', prefix='tmp', dir=None): _f, path = tempfile.mkstemp(suffix, prefix, dir) os.close(_f) _remove_at_exit(path) return path

# Register a file to be removed at exit def _remove_at_exit(path): atexit.register(os.remove, path)