/dev/stu

Posted by stu at May 17th, 2010

Seeing”Realtime FFT Graph of Audio WAV File or Microphone Input with Python…”  on python.reddit.com reminded me of one I’d built in python with shoebot.

While it works OK, I feel like I’m missing a higher level audio library (especially having seen Minim, for C++ and Java).

To run it in shoebot:

sbot -w audiobot.bot

audiobot.bot

# Major library imports
import atexit
import pyaudio
from numpy import zeros, short, fromstring, array
from numpy.fft import fft

NUM_SAMPLES = 512
SAMPLING_RATE = 11025

def setup():
    size(350, 260)
    speed(SAMPLING_RATE / NUM_SAMPLES)

_stream = None

def read_fft():
    global _stream
    pa = None

    def cleanup_audio():
        if _stream:
            _stream.stop_stream()
            _stream.close()
        pa.terminate()

    if _stream is None:
        pa = pyaudio.PyAudio()
        _stream = pa.open(format=pyaudio.paInt16, channels=1,
                           rate=SAMPLING_RATE,
                           input=True, frames_per_buffer=NUM_SAMPLES)
        atexit.register(cleanup_audio)

    audio_data  = fromstring(_stream.read(NUM_SAMPLES), dtype=short)
    normalized_data = audio_data / 32768.0

    return fft(normalized_data)[1:1+NUM_SAMPLES/2]

def flatten_fft(scale = 1.0):
    """
    Produces a nicer graph, I'm not sure if this is correct
    """
    for i, v in enumerate(read_fft()):
        yield scale * (i * v) / NUM_SAMPLES

def triple(audio):
    '''return bass/mid/treble'''
    c = audio.copy()
    c.resize(3, 255 / 3)
    return c

def draw():
    '''Draw 3 different colour graphs'''
    global NUM_SAMPLES
    audio = array(list(flatten_fft(scale = 80)))
    freqs = len(audio)
    bass, mid, treble = triple(audio)

    colours = (0.5, 1.0, 0.5), (1, 1, 0), (1, 0.2, 0.5)

    fill(0, 0, 1)
    rect(0, 0, WIDTH, 400)
    translate(50, 200)

    for spectrum, col in zip((bass, mid, treble), colours):
        fill(col)
        for i, s in enumerate(spectrum):
            rect(i, 0, 1, -abs(s))
        else:
            translate(i, 0)

    audio = array(list(flatten_fft(scale = 80)))

Posted by stu at May 12th, 2010

Often it’s useful to be able to store up drawing commands so you can use them later somewhere else (or even just pass them to another thread).

This is a simple drawing model, implemented in cairo, hopefully somebody will find it useful.

Queue

class DrawQueue:
    '''
    A list of draw commands, stored as callables that, are
    passed a set of parameters to draw on from the canvas
    implementation.
    '''
    def __init__(self, render_callables = None):
        self.render_callables = render_callables or deque()

    def append(self, render_callable):
        '''
        Add a render callable to the queue
        '''
        self.render_callables.append(render_callable)

    def render(self, cairo_ctx):
        '''
        Call all the render callables with cairo_ctx
        '''
        for render_callable in self.render_callables:
            render_callable(cairo_ctx)

The queue just accepts callables (any old function), and calls them when you call render, passing them a cairo context you pass in.

To get useful functions you can call closure functions like these:

def paint_closure():
    def paint(ctx):
        ctx.paint()
    return paint

def fill_closure():
    def fill(ctx):
        ctx.fill()
    return fill

def set_source_rgb_closure(r, g, b):
    def set_source_rgb(ctx):
        ctx.set_source_rgb(r, g, b)
    return set_source_rgb

def moveto_closure(x, y):
    def moveto(ctx):
        ctx.move_to(x, y)
    return moveto

def rectangle_closure(x, y, w, h):
    def rectangle(ctx):
        ctx.rectangle(x, y, w, h)
    return rectangle

Adding commands to the queue is simple:

dq = DrawQueue()
dq.append(set_source_rgb_closure(1, 1, 1))
dq.append(paint_closure())
dq.append(moveto_closure(10, 0))
dq.append(rectangle_closure(0, 0, 20, 20))
dq.append(set_source_rgb_closure(0, 0, 0))
dq.append(fill_closure())

This is the same drawing model I’m using in my branch of shoebot, I’m hoping to expand it to be multithreaded; while a foreground thread adds commands a background thread is executing them.

Here it is all put together in a simple example to draw a black rectangle

from collections import deque
import cairo

class DrawQueue:
    '''
    A list of draw commands, stored as callables that, are
    passed a set of parameters to draw on from the canvas
    implementation.
    '''
    def __init__(self, render_callables = None):
        self.render_callables = render_callables or deque()

    def append(self, render_callable):
        '''
        Add a render callable to the queue
        '''
        self.render_callables.append(render_callable)

    def render(self, cairo_ctx):
        '''
        Call all the render callables with cairo_ctx
        '''
        for render_callable in self.render_callables:
            render_callable(cairo_ctx)

#### drawing closures
def paint_closure():
    def paint(ctx):
        ctx.paint()
    return paint

def fill_closure():
    def fill(ctx):
        ctx.fill()
    return fill

def set_source_rgb_closure(r, g, b):
    def set_source_rgb(ctx):
        ctx.set_source_rgb(r, g, b)
    return set_source_rgb

def moveto_closure(x, y):
    def moveto(ctx):
        ctx.move_to(x, y)
    return moveto

def rectangle_closure(x, y, w, h):
    def rectangle(ctx):
        ctx.rectangle(x, y, w, h)
    return rectangle

#### /drawing closures

dq = DrawQueue()

# Add some commands to the drawing queue
dq.append(set_source_rgb_closure(1, 1, 1))
dq.append(paint_closure())
dq.append(moveto_closure(10, 0))
dq.append(rectangle_closure(0, 0, 20, 20))
dq.append(set_source_rgb_closure(0, 0, 0))
dq.append(fill_closure())

# Create a surface and context
surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, 200, 200)
ctx = cairo.Context(surface)

# run defered rendering
dq.render(ctx)

surface.write_to_png('output.png')

Posted by stu at February 3rd, 2010

Cairo is a 2D vector graphics api used by Firefox, Gtk and other desktop projects.

I’m going to show here that it can also be used to generate web content, using Django.

I’m going to port two examples from the Michael Urmans Cairo Tutorial for PyGTK Programmers.

To understand the cairo and it’s drawing model I’d recommend his his Cairo Tutorial for Python Programmers.

Note: In this example I’ll be generating SVGs…  as I.E. (as of 2010) does not support them, you might want to generate PNG or PDF – if you need to do this with cairo, look for one of the many cairo tutorials on the web.

The example django project can be downloaded at the end of the article.

(more…)

Posted by stu at September 6th, 2009

Stoyan of PHPIED.com has found the joy using javascript for scripting in the OS…

I’ve put up a few scripts I find useful in windows (download at the end of the article):

• addpath.js – Add a path to the registry path.
• dt.cmd – Change to desktop folder.
• e.cmd – Open explorer in current or specified folder.
• regpath.js  – Output the path stored in the registry.
• updateenvironment.js – Updates running apps with any changed settings in the registry.

And a couple that use python and pywin32:

• ccwd.py – Copy the current working directory to the clipboard
• cpath.py – Copy the current path to the clipboard

All of have acompanying batch files to run them, I generally have everything in a folder c:\usr\cmd, but they should work from anywhere in the path.

Download  cmd.zip

Posted by stu at August 21st, 2009

I recently came across Java2Python.  As I’m interested in Cairo I thought it would be interesting to try porting one of the example tutorials from ZetCode.

I’ll run through the steps involved in porting then try and reach some conclusions at the end .

1. Get setup

This is easiest in Linux, I’m running Ubuntu (in vmware), and installed

antlr 2.x
python2.5.x
sun java6
pygtk
java-gnome

You can install them like this:

# sudo apt-get install antlr python2.5 sun-java6-bin libjava-gnome-java

Then install Python2Java with easy_install

# sudo easy_install-2.5 java2python

To test if it’s working run j2py -i.  It should complain there is no file:

# j2py -i
Usage: j2py [options]

j2py: error: -i option requires an argument

If you get any other errors your missing some packages.

2. Get the Java Code from the Simple Example.

Save the ’simple.java’ example as ‘GSimple.java’

If java-gnome is running ok, compiling and running it you should see a window:

# javac GSimple.java
# java GSimple

Posted by stu at February 26th, 2008

I’ve recently been learning python and decided to note down the *very basics* that took longer to find out than I would’ve liked.

Without furtherado, heres my 5-minute-python.