Creates waveform image from wave file.

waveform.py

import numpy
from PIL import Image, ImageDraw
import scikits.audiolab as audiolab


class Waveform(object):
    """Creates a waveform image for given wave audio file.

    :param soundfile: The path to the wave file.
    :param width: The output image width as an optional integer.
    :param height: The output image height as an optional integer.
    :param background: The output image background color as an optional
        RGBA tupple.
    :param line: The output image line color as an optional RGBA tupple.
    """
    def __init__(self, soundfile, width=1000, height=200,
            background=(255, 255, 255, 255), line=(0, 0, 0, 0)):
        # Loads the wave file
        self.snd = audiolab.Sndfile(soundfile, 'r')

        self.width = width
        self.height=height
        self.background = background
        self.line = line

        # Reads all frames
        self.frames = self.snd.read_frames(self.snd.nframes)

        # Keep only one channel
        if self.snd.channels == 2:
            self.frames = self.frames[0::2]

        # Frames to read for one pixel width
        self.nframes_per_pixel = len(self.frames) / self.width

    def draw(self):
        """Returns the waveform as PIL Image."""
        image = Image.new("RGBA", (self.width, self.height), self.background)
        draw = ImageDraw.Draw(image)
        for x in range(0, self.width):
            value = self.get_value_for_x(x)
            draw.line([
                x,
                int(self.height) / 2 + value,
                x,
                int(self.height) / 2 - value
            ], self.line)
        return image

    def get_value_for_x(self, x):
        """Returns the max value for given `x`.

        :param x: The x position in pixel.
        """
        frames = self.frames[x * self.nframes_per_pixel: (x + 1) \
                * self.nframes_per_pixel]
        return int(numpy.abs(frames).max() * (self.height / 2))

    def save(self, path):
        """Saves the waveform images.

        :param path: The destination path.
        """
        image = self.draw()
        image.save(path)