Removing white sections in spectrogram

Question

I am creating spectrograms from audio files, but in several sections, I am getting white background. I would prefer the white sections to be transparent. For instance my current spectrogram :

My desired spectrogram:

My current code for .wav files to spectrogram

def spectrogram_from_wav():
results = ['Positive', 'Negative', 'Unknown']
for res in results: 
    pathlib.Path(f"spectrograms/{res}").mkdir(parents=True, exist_ok=True)
    for files in tqdm(os.listdir(f"./cleaned_data/{res}")):
        filename = f"cleaned_data/{res}/{files}"
        #print(filename)
        x, sr = librosa.load(filename, mono=True)
        plt.specgram(x, NFFT=2048, Fs=2, Fc=0, noverlap=128, cmap='inferno', sides='default', mode='default', scale='dB');
        plt.axis('off');
        #plt.savefig(f"./spectrograms/{res}/{files[:-4]}.png")
        plt.clf()
        plt.show()

I tried that method and it doesn't work. Thank you! – Blacky_99 Jan 15 '21 at 17:26 — Blacky_99, Jan 15 '21 at 17:26

Roman Pavelka · Accepted Answer · 2021-01-16T20:13:13.497

2

Notice that the savefig has transparent option:

https://matplotlib.org/3.1.1/api/_as_gen/matplotlib.pyplot.savefig.html

How to export plots from matplotlib with transparent background?

edited Jan 16 '21 at 20:13

answered Jan 15 '21 at 15:31

Roman Pavelka

692
2
12

It just saves me a black image now – Blacky_99 Jan 15 '21 at 15:40
That is strange, if you would try to save a trivial example `plt.plot([0, 0])` with `plt.savefig("x.png", transparent=True)` that does work? – Roman Pavelka Jan 15 '21 at 15:51
Transparent now still save my image as usual. There are no changes – Blacky_99 Jan 15 '21 at 17:40
Strange, it works here on my machine. You can work around it using imagemagick's convert as a postprocessing step: https://stackoverflow.com/questions/12424018/how-to-replace-white-background-color-with-transparent-of-an-image-in-imagemagic – Roman Pavelka Jan 15 '21 at 17:44
there was an issue with my matplotlib installation. After reinstalling the transparent option works! Thank you very much! – Blacky_99 Jan 15 '21 at 17:48
Great! You are welcome! :) – Roman Pavelka Jan 16 '21 at 20:13

Removing white sections in spectrogram

1 Answers1