# Copyright 2013 Philip N. Klein """ A module for working with images in matrix format. An image is represented by two matrices, representing points and colors. The points matrix has row labels {'x', 'y', 'u'} and column labels (0,0) through (w, h), inclusive, where (w, h) are the width and height of the original image The colors matrix has row labels {'r', 'g', 'b'} and column labels (0,0) through (w-h, h-1). The column labels for these matrices represent "lattice points" on the original image. For pixel (i,j) in the original image, the (i,j) column in the colors matrix represents the pixel color and the (i,j), (i+1, j), (i+1, j+1), and (i, j+1) columns in the points matrix represent the boundary of the pixel region """ import mat import png import numbers import collections import webbrowser import tempfile import os import atexit import math # 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 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 return [[int(0.2126*p + 0.7152*p + 0.0722*p) 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))] 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), 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) def file2mat(path, row_labels = ('x', 'y', 'u')): """input: a filepath to an image in .png format output: the pair (points, matrix) of matrices representing the image.""" return image2mat(file2image(path), row_labels) def image2mat(img, row_labels = ('x', 'y', 'u')): """ input: an image in list-of-lists format output: a pair (points, colors) of matrices representing the image. Note: The input list-of-lists can consist of either integers n [0, 255] for grayscale or 3-tuple of integers representing the rgb color coordinates """ h = len(img) w = len(img) rx, ry, ru = row_labels ptsD = (set(row_labels), {(x,y) for x in range(w+1) for y in range(h+1)}) ptsF = {} colorsD = ({'r', 'g', 'b'}, {(x,y) for x in range(w) for y in range(h)}) colorsF = {} for y in range(h+1): for x in range(w+1): pt = (x,y) ptsF[(rx, pt)] = x ptsF[(ry, pt)] = y ptsF[(ru, pt)] = 1 if x < w and y < h: col = img[y][x] if type(col) is int: red, green, blue = col, col, col else: red, green, blue = col colorsF[('r', pt)] = red colorsF[('g', pt)] = green colorsF[('b', pt)] = blue return mat.Mat(ptsD, ptsF), mat.Mat(colorsD, colorsF) def mat2display(pts, colors, row_labels = ('x', 'y', 'u'), scale=1, xscale=None, yscale = None, xmin=0, ymin=0, xmax=None, ymax=None, crosshairs=False, browser=None): """ input: matrix pts and matrix colors representing an image result: Displays the image in a web browser Optional arguments: row_labels - A collection specifying the points matrix row labels, in order. The first element of this collection is considered the x coordinate, the second is the y coordinate, and the third is the u coordinate, which is assumed to be 1 for all points. scale - The display scale, in pixels per image coordinate unit xscale, yscale - in case you want to scale differently in x and y xmin, ymin, xmax, ymax - The region of the image to display. These can be set to None to use the minimum/maximum value of the coordinate instead of a fixed value. crosshairs - Setting this to true displays a crosshairs at (0, 0) in image coordinates browser - A browser string to be passed to webbrowser.get(). Overrides the module default, if any has been set. """ if xscale == None: xscale = scale if yscale == None: yscale = scale rx, ry, ru = row_labels if ymin is None: ymin = min(v for (k, v) in pts.f.items() if k == ry) if xmin is None: xmin = min(v for (k, v) in pts.f.items() if k == rx) if ymax is None: ymax = max(v for (k, v) in pts.f.items() if k == ry) if xmax is None: xmax = max(v for (k, v) in pts.f.items() if k == rx) # Include (0, 0) in the region if crosshairs: ymin = min(ymin, 0) xmin = min(xmin, 0) ymax = max(ymax, 0) xmax = max(xmax, 0) hpath = _create_temp('.html') with open(hpath, 'w') as h: h.writelines( ['\n', ' image \n', '\n', '\n', '\n', '\n']) openinbrowser('file://%s' % hpath, browser) print("Hit Enter once the image is displayed.... ", end="") input()