ComfyUI Radial Average Amplitude Spectrum

A ComfyUI custom node that computes and visualizes the Radial Average Amplitude Spectrum of an input image — a 1D frequency-domain analysis tool useful for characterizing image texture, noise, and spatial frequency content.

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What It Does

1. Converts the input image to grayscale using luminance weights.
2. Applies a 2D FFT and shifts the DC component to the center.
3. Computes the amplitude spectrum (|FFT|).
4. Averages the amplitude values at each integer radial distance from the center, producing a 1D spectrum.
5. Renders the spectrum as a log-log plot and returns it as a standard ComfyUI IMAGE tensor.

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Installation

Option A — Copy into custom_nodes

cp -r ComfyUI_RadialAvgAmpSpectrum /path/to/ComfyUI/custom_nodes/

Option B — Clone directly

cd /path/to/ComfyUI/custom_nodes
git clone https://github.com/your-repo/ComfyUI_RadialAvgAmpSpectrum.git

Then restart ComfyUI. The node will appear under the analysis category.

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Dependencies

All dependencies are part of the standard Python scientific stack that ComfyUI already ships with:

| Package | Purpose | |---------|---------| | numpy | FFT and array operations | | matplotlib | Plot rendering | | Pillow | Image conversion | | torch | Tensor I/O (ComfyUI standard) |

No additional pip install steps are required in a typical ComfyUI environment.

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Node Reference

Node name: Radial Avg Amplitude Spectrum Category: analysis

Inputs

| Name | Type | Description | |------|------|-------------| | image | IMAGE | Input image (any resolution, RGB or grayscale) | | plot_width | INT | Width of the output plot image in pixels (default: 512) | | plot_height | INT | Height of the output plot image in pixels (default: 512) | | line_color | STRING | Matplotlib color string for the spectrum line (default: red) | | log_x | BOOLEAN | Use logarithmic scale on the frequency axis (default: true) | | log_y | BOOLEAN | Use logarithmic scale on the amplitude axis (default: true) |

Outputs

| Name | Type | Description | |------|------|-------------| | spectrum_image | IMAGE | Log-log plot of the 1D radial average amplitude spectrum |

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Interpreting the Output

• X axis (frequency): Spatial frequency in cycles per pixel, expressed as radial distance from the DC center (1 = lowest non-DC frequency, Nyquist ≈ min(H,W)/2).
• Y axis (amplitude): Mean amplitude of the FFT at that radial frequency bin.
• A steep negative slope indicates a smooth, low-frequency-dominant image.
• A flat or slowly decaying spectrum indicates high-frequency content (sharp edges, noise, fine texture).

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License

MIT