SigMF XY O-Scope Logo (.sigmf to .svg)

sigmf_to_svg.py

#!/usr/bin/env python3
'''code to render SigMF logo as nice SVG via oscillioscope'''
import matplotlib.pyplot as plt
import numpy as np
from sigmf import sigmffile
from scipy.signal import resample_poly

# load data
signal = sigmffile.fromfile('sigmf_logo')
# signal = sigmffile.fromfile('sigmf_logo_fullband')
samples = signal.read_samples(0, signal.sample_count)
samp_rate = signal.get_global_field('core:sample_rate')

# drawing parameters
framerate = 60
frames = 6 * framerate
width_decay = 4
interp = 4 if samp_rate == 48000 else 1
intensity = 1/frames * 1000 * interp
if interp == 4:
    intensity *= 500
blocksize = int(signal.sample_count/frames)
colors = plt.get_cmap('viridis')(np.linspace(0, 1, blocksize*interp))
full_scale = 10*10**(-14/10) # -14 LUFS
fade = True

for fdx in range(0, frames):
    if fdx != 244:
        # 244 is our logo frame at 60fps
        continue
    #if fdx*blocksize < 3.875*samp_rate:
    #    # logo is steady in this region
    #    continue
    chunk = samples[fdx*blocksize:(fdx+1)*blocksize]
    if interp > 1:
        # smooth out transitions
        chunk = resample_poly(chunk, interp, 1)
    # distance between points proportional to line width
    distances = np.array([np.linalg.norm(x) for x in chunk[1:]-chunk[:-1]])
    points = chunk.reshape(-1, 1, 2)
    segments = np.concatenate([points[:-1], points[1:]], axis=1)
    widths = (distances.max()-distances)**width_decay * intensity
    if fade:
        # tail off intensity of oldest points
        # widths = widths * np.geomspace(.001, 1, num=len(widths))
        glow = np.ones_like(widths)
        fade_count = len(glow)//4
        glow[0:fade_count] = np.linspace(0,1,fade_count+1)[1:]
        widths *= glow
    # draw
    scale = .9
    plt.figure(figsize=(9,9))
    ax = plt.gca()
    for kdx in range(len(segments)-1):
        segment = segments[kdx]
        # was using LineCollection, but doesn't set capstyles correctly per
        # https://stackoverflow.com/questions/38079366/matplotlib-line3dcollection-multicolored-line-edges-are-jagged
        line, = ax.plot(segment[:,0], segment[:,1], color='k', linewidth=widths[kdx])
        line.set_solid_capstyle('round')

    if fdx == 244:
        plt.xlim(-full_scale, full_scale)
        plt.ylim(-full_scale, full_scale)
        plt.gca().set_axis_off()
        #plt.savefig('/tmp/out.svg', bbox_inches='tight', pad_inches=0, edgecolor='none', facecolor=plt.gcf().get_facecolor())
    else:
        plt.xlim(-full_scale*scale, full_scale*scale)
        plt.ylim(-full_scale*scale, full_scale*scale)
        plt.title(f'{fdx*blocksize/samp_rate:.2f} thru {(fdx+1)*blocksize/samp_rate:.2f} ({fdx*blocksize} thru {(fdx+1)*blocksize})')
    plt.show()

    # investigate linewidth distribution
    # plt.figure()
    # plt.plot(widths)
    # plt.show()

This code was used to generate the official SigMF logo.