commit 78448f953bae662872e00c13f99d7befa8c7dd92
Author: Hsiaoming Yang <me@lepture.com>
Date:   Tue Nov 25 18:05:00 2014 +0800

    Init with audio captcha

diff --git a/captcha/__init__.py b/captcha/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/captcha/audio.py b/captcha/audio.py
new file mode 100644
index 0000000..1d3fe1f
--- /dev/null
+++ b/captcha/audio.py
@@ -0,0 +1,216 @@
+# coding: utf-8
+
+import os
+import copy
+import wave
+import struct
+import random
+
+
+WAVE_SAMPLE_RATE = 8000  # HZ
+WAVE_HEADER = bytearray(
+    b'RIFF\x00\x00\x00\x00WAVEfmt \x10\x00\x00\x00\x01\x00\x01\x00'
+    b'@\x1f\x00\x00@\x1f\x00\x00\x01\x00\x08\x00data'
+)
+WAVE_HEADER_LENGTH = len(WAVE_HEADER) - 4
+DATA_DIR = os.path.join(os.path.abspath(os.path.dirname(__file__)), 'data')
+
+
+def _read_wave_file(filepath):
+    w = wave.open(filepath)
+    data = w.readframes(-1)
+    w.close()
+    return data
+
+
+def change_speed(body, speed=1):
+    """Change the voice speed of the wave body."""
+    if speed == 1:
+        return body
+
+    length = int(len(body) * speed)
+    rv = bytearray(length)
+
+    step = 0
+    for v in body:
+        i = int(step)
+        while i < int(step + speed) and i < length:
+            rv[i] = v
+            i += 1
+        step += speed
+    return rv
+
+
+def patch_wave_header(body):
+    """Patch header to the given wave body.
+
+    :param body: the wave content body, it should be bytearray.
+    """
+    assert isinstance(body, bytearray)
+
+    length = len(body)
+
+    padded = length + length % 2
+    total = WAVE_HEADER_LENGTH + padded
+
+    header = copy.copy(WAVE_HEADER)
+    # fill the total length position
+    header[4:8] = bytearray(struct.pack('<I', total))
+    header += bytearray(struct.pack('<I', length))
+
+    data = header + body
+
+    # the total length is even
+    if length != padded:
+        data = data + bytearray([0])
+
+    return data
+
+
+def create_noise(length, level=4):
+    """Create white noise for background"""
+    noise = bytearray(length)
+    adjust = 128 - level / 2
+    i = 0
+    while i < length:
+        v = random.randint(0, 256)
+        noise[i] = v % level + adjust
+        i += 1
+    return noise
+
+
+def create_silence(length):
+    """Create a piece of silence."""
+    data = bytearray(length)
+    i = 0
+    while i < length:
+        data[i] = 128
+        i += 1
+    return data
+
+
+def change_sound(body, level=1):
+    assert isinstance(body, bytearray)
+
+    if level == 1:
+        return body
+
+    body = copy.copy(body)
+    for i, v in enumerate(body):
+        if v > 128:
+            v = (v - 128) * level + 128
+            v = max(int(v), 128)
+            v = min(v, 256)
+        elif v < 128:
+            v = 128 - (128 - v) * level
+            v = min(int(v), 128)
+            v = max(v, 0)
+        body[i] = v
+    return body
+
+
+def mix_wave(src, dst):
+    """Mix two wave body into one."""
+    if len(src) > len(dst):
+        # output should be longer
+        dst, src = src, dst
+
+    for i, sv in enumerate(src):
+        dv = dst[i]
+        if sv < 128 and dv < 128:
+            dst[i] = sv * dv / 128
+        else:
+            dst[i] = 2 * (sv + dv) - sv * dv / 128 - 256
+    return dst
+
+
+BEEP = bytearray(_read_wave_file(os.path.join(DATA_DIR, 'beep.wav')))
+END_BEEP = change_speed(BEEP, 1.4)
+SILENCE = create_silence(WAVE_SAMPLE_RATE / 5)
+
+
+class AudioCaptcha(object):
+    def __init__(self, voicedir=None):
+        if voicedir is None:
+            voicedir = DATA_DIR
+        self._voicedir = voicedir
+        self._cache = {}
+
+    def load(self):
+        for n in os.listdir(self._voicedir):
+            if len(n) == 1 and os.path.isdir(os.path.join(self._voicedir, n)):
+                self._load_data(n)
+
+    def _load_data(self, name):
+        dirname = os.path.join(self._voicedir, name)
+        data = []
+        for f in os.listdir(dirname):
+            filepath = os.path.join(dirname, f)
+            if f.endswith('.wav') and os.path.isfile(filepath):
+                data.append(bytearray(_read_wave_file(filepath)))
+        self._cache[name] = data
+
+    def twist_pick(self, key):
+        voice = random.choice(self._cache[key])
+
+        # random change speed
+        speed = random.randrange(90, 120) / 100.0
+        voice = change_speed(voice, speed)
+
+        # random change sound
+        level = random.randrange(80, 120) / 100.0
+        voice = change_sound(voice, level)
+        return voice
+
+    def pick_for_background(self):
+        key = random.choice(self._cache.keys())
+        voice = random.choice(self._cache[key])
+        voice = copy.copy(voice)
+        voice.reverse()
+
+        speed = random.randrange(8, 16) / 10.0
+        voice = change_speed(voice, speed)
+
+        level = random.randrange(2, 6) / 10.0
+        voice = change_sound(voice, level)
+        return voice
+
+    def create_background_noise(self, length, chars):
+        noise = create_noise(length, 4)
+        pos = 0
+        while pos < length:
+            sound = self.pick_for_background()
+            end = pos + len(sound) + 1
+            noise[pos:end] = mix_wave(sound, noise[pos:end])
+            pos = end + random.randint(0, WAVE_SAMPLE_RATE / 10)
+        return noise
+
+    def create_wave_body(self, chars):
+        voices = []
+        inters = []
+        for key in chars:
+            voices.append(self.twist_pick(key))
+            v = random.randint(WAVE_SAMPLE_RATE, WAVE_SAMPLE_RATE * 3)
+            inters.append(v)
+
+        durations = map(lambda a: len(a), voices)
+        l = max(durations) * len(chars) + reduce(lambda a, b: a + b, inters)
+        bg = self.create_background_noise(l, chars)
+
+        body = BEEP + SILENCE + BEEP + SILENCE + BEEP
+
+        # begin
+        pos = inters[0]
+        for i, v in enumerate(voices):
+            end = pos + len(v) + 1
+            bg[pos:end] = mix_wave(v, bg[pos:end])
+            pos = end + inters[i]
+
+        body += bg + END_BEEP
+        return body
+
+    def generate(self, chars):
+        if not self._cache:
+            self.load()
+        body = self.create_wave_body(chars)
+        return patch_wave_header(body)
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