Living Code

Just for fun, and because I'm trying out two things:

1. Using Ecto for posting again
2. Blogging more often

Here are my results from the latest craze:

$ history|awk '{a[$2]++} END{for(i in a){printf "%5d\t%s\n",a[i],i}}'|sort -rn|head
139 ls
87 cd
54 python
43 /usr/bin/python
38 less
21 vim
16 clear
12 mate
11 rm
10 ssh

The first python is the one I built from source so I can include it in applications packaged with py2app, the second is the built-in python for Leopard. Both are version 2.5. The mate program is used to open files in TextMate from the command line.

I want to create a new superhero.

He's going to be exactly like Captain Marvel except that instead of saying "Shazam!" he's going to say "Zapdoodle!"

And instead of being Aryan he's going to be vaguely multi-ethnic.

And instead of battling generalized injustice he will fight a specific injustice, like homelessness or suburban sprawl.

And instead of having popular support people will mock him and try to have him arrested.

And instead of having a uniform of red spandex he will have a uniform of random clothes from Salvation Army.

And instead of having a sidekick he will have his sides kicked when he sleeps on the street.

And instead of having a secret identity, people just won't really care who he is.

And instead of being young, tall, athletic and arguably handsome, he will be short, pudgy, and middle-aged, with a pronounced limp.

OK, so he's not going to be much like Captain Marvel at all.

But he will say "Zapdoodle!"

In fact, he may not say anything else, ever.

Just a reminder for Pythonistas in the Vancouver area: The Vancouver Python and Zope user group (VanPyZ) is tomorrow (Tuesday, April 1). Paul Prescod will be talking about metaprogramming in Python. Details and directions are on the VanPyZ site. And, as usual, we'll be heading out to the pub afterwards for more discussion.

Hope to see you there!

The latest version, 1.8, of PyGame can save PNGs directly from a Surface: pygame.Image.save(mySurface, 'myimagefile.png'). But what if you want to support an older version of PyGame, such as the one available for the N800 or the XO? Well, assuming you have access to the Python Image Library, you can use that:

import Image # from PIL
import pygame

def pygame_to_pil_img(pg_surface):
    imgstr = pygame.image.tostring(pg_surface, 'RGB')
    return Image.fromstring('RGB', pg_surface.get_size(), imgstr)

def pil_to_pygame_img(pil_img):
    imgstr = pil_img.tostring()
    return pygame.image.fromstring(imgstr, pil_img.size, 'RGB')

Once you have a PyGame Image, you can save it to PNG easily: myImage.save('myfilename.png')

I've found myself looking for this code snippet more than once, now I can Google for it more readily, and maybe someone else will find it helpful too.

The other day, Thomas Guest talked about drawing chessboards, and ended with a challenge. I wanted to answer a different challenge, however. What if, instead of drawing on a rectangular grid, we wanted to draw on a hexagonal grid? The following is my slapdash answer. For real-world use I'd make nice classes and pass more parameters to the methods, but to demonstrate the math I'm just going to use global constants and functions.

Like Thomas' article, I will show solutions using several different tools, in this case Apple's Core Graphics, PyGame, Python Imaging Library (PIL), and SVG. All of these solutions will use the same constants and math:

# Constants used by each solution

from math import sin, cos, pi, sqrt
THETA = pi / 3.0 # Angle from one point to the next
HEXES_HIGH = 8 # How many rows of hexes
HEXES_WIDE = 5 # How many hexes in a row
RADIUS = 30 # Size of a hex
HALF_RADIUS = RADIUS / 2.0
HALF_HEX_HEIGHT = sqrt(RADIUS ** 2 - HALF_RADIUS ** 2)
IMAGE_WIDTH = int(RADIUS * (HEXES_WIDE * 3 + .5))
IMAGE_HEIGHT = int(HALF_HEX_HEIGHT * (HEXES_HIGH + 1))

# Functions (generators) used by each solution

def hex_points(x,y):
    '''Given x and y of the origin, return the six points around the origin of RADIUS distance'''
    for i in range(6):
        yield cos(THETA * i) * RADIUS + x, sin(THETA * i) * RADIUS + y

def hex_centres():
    for x in range(HEXES_WIDE):
        for y in range(HEXES_HIGH):
            yield (x * 3 + 1) * RADIUS + RADIUS * 1.5 * (y % 2), (y + 1) * HALF_HEX_HEIGHT

Now, given the above, what does the code look like to draw the hexes? Because each library handles colours slightly differently, we will need a generator for colours (and we will need more than just black and white as the chessboard used, because each hex borders on six others). I haven't given a lot of thought to optimal colouring schemes: each colour generator simply produces red, yellow, blue, and green in a cycle. Here is the image produced by the Core Graphics solution, followed by the code:

def quartz_colours():
    while True:
        yield 1,0,0,1 # red
        yield 1,1,0,1 # yellow
        yield 0,0,1,1 # blue
        yield 0,1,0,1 # green

def quartz_hex():
    '''Requires a Mac with OS 10.4 or better and the Developer Tools installed'''
    import CoreGraphics as cg
    colours = quartz_colours()
    cs = cg.CGColorSpaceCreateDeviceRGB()
    c = cg.CGBitmapContextCreateWithColor(IMAGE_WIDTH, IMAGE_HEIGHT, cs, (0,0,0,.2))
    c.saveGState()
    c.setRGBStrokeColor(0,0,0,0)
    c.setLineWidth(0)
    for x,y in hex_centres():
        c.beginPath()
        c.setRGBFillColor(*colours.next())
        points = list(hex_points(x,y))
        c.moveToPoint(*points[-1])
        [c.addLineToPoint(*pt) for pt in points]
        c.drawPath(cg.kCGPathFill)
    c.restoreGState()
    c.writeToFile("quartz_hexes.png", cg.kCGImageFormatPNG)

Now for some cross-platform examples. Here is the image generated by PyGame, followed by that code:

def pygame_colours():
    while True:
        yield 255, 0, 0 # red
        yield 255, 255, 0 # yellow
        yield 0, 0, 255 # blue
        yield 0, 255, 0 # green

def pygame_hex():
    '''Requires PyGame 1.8 or better to save as PNG'''
    import pygame
    pygame.init()
    screen = pygame.display.set_mode((IMAGE_WIDTH, IMAGE_HEIGHT))
    colours = pygame_colours()
    for x,y in hex_centres():
        pygame.draw.polygon(screen, colours.next(), list(hex_points(x,y)))
    pygame.image.save(screen, 'pygame_hexes.png')

When you run the PyGame script, it will actually pop up a window very briefly, draw into the window, save the result, and close the window. I also didn't get the PyGame script to add transparency for the background, although I think it could be added fairly easily. Now, for the web, here is a solution in SVG, with the image captured by screenshot in Safari, followed by the Python code, and the resulting SVG code:

def svg_colours():
    while True:
        yield 'rgb(255, 0, 0)'
        yield 'rgb(255, 255, 0)'
        yield 'rgb(0, 0, 255)'
        yield 'rgb(0, 255, 0)'

def svg_hex():
    out = open('svg_hexes.svg', 'w')
    print >> out, '''<?xml version="1.0" standalone="no"?>
    <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
    <svg width="%spx" height="%spx" version="1.1" xmlns="http://www.w3.org/2000/svg">''' % (IMAGE_WIDTH, IMAGE_HEIGHT)
    colours = svg_colours()
    for pt in hex_centres():
        print >> out, '<polygon fill="%s" stroke-width="0" points="%s" />' % (colours.next(),  ' '.join(["%s,%s" % (x,y) for (x,y) in hex_points(*pt)]))
    print >> out, '</svg>'
    out.close()

And here is the SVG created by the above script: SVG Hexes

Finally, one library which overlaps with the ones used by the Chessboard example: Python Imaging Library.

pil_colours = pygame_colours  # same format works, so we'll re-use it

def pil_hex():
    import Image, ImageDraw
    image = Image.new("RGBA", (IMAGE_WIDTH,IMAGE_HEIGHT), (0,0,0,0))
    colours = pil_colours()
    draw = ImageDraw.Draw(image)
    for x,y in hex_centres():
        draw.polygon(list(hex_points(x,y)), fill=colours.next())
    image.save('pil_hexes.png', 'PNG')

That's it for my examples. Thomas ended with a challenge for displaying chess, and for describing the position. To describe the position, I would use a standard chess notation, such as described here. For my challenge, what other formats would be useful to create hex maps in? POVRay? Flash? Any other examples out there?