I have Pillow 2.4.0 installed (both in virtual env on OS X and on Ubuntu 14.04 EC2). I wrote the following script to create a waveform visualization ( inspiring Jiaaro ). It uses the Pydub library to analyze waveforms and the ImageDraw function from PIL / Pillow to draw lines. The wav variable is audiosegment () (from the Pydub library), imgname is the line:
def draw_waveform(wav, imgname, color="#000000", w=400, h=40):
sound = wav
name = imgname
width = w
height = h
color = color
chunk_length = len(sound) / width
loudness_of_chunks = [
sound[ i*chunk_length : (i+1)*chunk_length ].rms
for i in range(width)]
max_rms = max(loudness_of_chunks)
scale = max_rms/(height/2)
size = (width,height)
im = Image.new('RGBA', size, (255, 255, 255, 255))
draw = ImageDraw.Draw(im)
for i in range(1, width):
pos = (width - i, height/2 + loudness_of_chunks[i]/scale-4)
draw.line((width - i,height/2) + pos, fill=color)
pos = (width - i, height/2 - loudness_of_chunks[i]/scale+4)
draw.line((width - i,height/2) + pos, fill=color)
del draw
im.rotate(180).save(app.config['UPLOAD_FOLDER'] + '/' + name, 'GIF', transparency=0) #, transparency=0
return app.config['UPLOAD_FOLDER'] + '/' + name
All groovy, most of the time. On some waveforms, in particular, it seems that those closest to the peak, PIL will produce a GIF that reverses the transparency — the waveform will be transparent and the space around it will be white. Usually the background is transparent and the waveform is black (# 000000).
Here is an image of the expected result:
( save-as , , ):
- ? - ()?