{"spec_id":"spectrogram-basic","library":"bokeh","language":"python","code":"\"\"\" anyplot.ai\nspectrogram-basic: Spectrogram Time-Frequency Heatmap\nLibrary: bokeh 3.9.0 | Python 3.13.13\nQuality: 90/100 | Updated: 2026-05-15\n\"\"\"\n\nimport os\nimport time\nfrom pathlib import Path\n\nimport numpy as np\nfrom bokeh.io import output_file, save\nfrom bokeh.models import BasicTicker, ColorBar, LinearColorMapper\nfrom bokeh.palettes import Viridis256\nfrom bokeh.plotting import figure\nfrom scipy import signal\nfrom selenium import webdriver\nfrom selenium.webdriver.chrome.options import Options\n\n\nTHEME = os.getenv(\"ANYPLOT_THEME\", \"light\")\nPAGE_BG = \"#FAF8F1\" if THEME == \"light\" else \"#1A1A17\"\nELEVATED_BG = \"#FFFDF6\" if THEME == \"light\" else \"#242420\"\nINK = \"#1A1A17\" if THEME == \"light\" else \"#F0EFE8\"\nINK_SOFT = \"#4A4A44\" if THEME == \"light\" else \"#B8B7B0\"\n\n# Data - Generate chirp signal with increasing frequency\nnp.random.seed(42)\nsample_rate = 8000\nduration = 2.0\nt = np.linspace(0, duration, int(sample_rate * duration), endpoint=False)\n\nf0 = 200\nf1 = 2000\nchirp_signal = signal.chirp(t, f0, duration, f1, method=\"linear\")\nchirp_signal += 0.1 * np.random.randn(len(chirp_signal))\n\n# Compute spectrogram\nnperseg = 256\nnoverlap = 192\nfrequencies, times, Sxx = signal.spectrogram(\n    chirp_signal, fs=sample_rate, nperseg=nperseg, noverlap=noverlap, scaling=\"density\"\n)\n\nSxx_db = 10 * np.log10(Sxx + 1e-10)\n\n# Create figure\np = figure(\n    width=4800,\n    height=2700,\n    title=\"spectrogram-basic · bokeh · anyplot.ai\",\n    x_axis_label=\"Time (seconds)\",\n    y_axis_label=\"Frequency (Hz)\",\n    x_range=(times.min(), times.max()),\n    y_range=(frequencies.min(), frequencies.max()),\n    tools=\"\",\n    toolbar_location=None,\n)\n\n# Color mapping\ncolor_mapper = LinearColorMapper(palette=Viridis256, low=Sxx_db.min(), high=Sxx_db.max())\n\n# Render spectrogram\np.image(\n    image=[Sxx_db],\n    x=times.min(),\n    y=frequencies.min(),\n    dw=times.max() - times.min(),\n    dh=frequencies.max() - frequencies.min(),\n    color_mapper=color_mapper,\n    level=\"image\",\n)\n\n# Colorbar\ncolor_bar = ColorBar(\n    color_mapper=color_mapper,\n    ticker=BasicTicker(),\n    label_standoff=15,\n    border_line_color=INK_SOFT,\n    location=(0, 0),\n    title=\"Power (dB)\",\n    title_text_font_size=\"24pt\",\n    major_label_text_font_size=\"18pt\",\n    width=60,\n    padding=30,\n)\np.add_layout(color_bar, \"right\")\n\n# Text styling\np.title.text_font_size = \"28pt\"\np.title.text_color = INK\np.xaxis.axis_label_text_font_size = \"22pt\"\np.yaxis.axis_label_text_font_size = \"22pt\"\np.xaxis.axis_label_text_color = INK\np.yaxis.axis_label_text_color = INK\np.xaxis.major_label_text_font_size = \"18pt\"\np.yaxis.major_label_text_font_size = \"18pt\"\np.xaxis.major_label_text_color = INK_SOFT\np.yaxis.major_label_text_color = INK_SOFT\n\n# Axes and grid\np.xaxis.axis_line_color = INK_SOFT\np.yaxis.axis_line_color = INK_SOFT\np.xaxis.major_tick_line_color = INK_SOFT\np.yaxis.major_tick_line_color = INK_SOFT\np.xgrid.grid_line_color = INK\np.ygrid.grid_line_color = INK\np.xgrid.grid_line_alpha = 0.10\np.ygrid.grid_line_alpha = 0.10\n\n# Background\np.background_fill_color = PAGE_BG\np.border_fill_color = PAGE_BG\np.outline_line_color = INK_SOFT\n\n# Legend styling\nif p.legend:\n    p.legend.background_fill_color = ELEVATED_BG\n    p.legend.border_line_color = INK_SOFT\n    p.legend.label_text_color = INK_SOFT\n\n# Save HTML\noutput_file(f\"plot-{THEME}.html\")\nsave(p)\n\n# Screenshot with Selenium\nW, H = 4800, 2700\nopts = Options()\nfor arg in (\n    \"--headless=new\",\n    \"--no-sandbox\",\n    \"--disable-dev-shm-usage\",\n    \"--disable-gpu\",\n    f\"--window-size={W},{H}\",\n    \"--hide-scrollbars\",\n):\n    opts.add_argument(arg)\ndriver = webdriver.Chrome(options=opts)\ndriver.set_window_size(W, H)\ndriver.get(f\"file://{Path(f'plot-{THEME}.html').resolve()}\")\ntime.sleep(3)\ndriver.save_screenshot(f\"plot-{THEME}.png\")\ndriver.quit()\n"}