gr-paint

Out-of-tree GNU Radio module available in GNU Radio World

An image transmitted and recovered as spectrum-painted artwork — Repository artwork

gr-paint is an OFDM transmitter that encodes monochrome images as visible shapes in a spectrum waterfall. It converts image rows into the frequency-bin magnitudes of a large inverse FFT, then repeats and cyclically prefixes the resulting time-domain lines to control their persistence and aspect ratio on a receiver display. An accompanying image source accepts common image formats, allowing arbitrary artwork, text, and test patterns to become transmit-ready IQ rather than requiring manually prepared raw luminance files.

Main author: Ron Economos
Last modified: 2025-08-24
Project: Upstream repository

Example flowgraphs

These GNU Radio World examples contain one or more blocks from gr-paint.

Paint a JPEG Into a WaterfallPaint a JPEG into a waterfall display. Same flowgraph as the PNG example, on a lossily compressed image; open the Image File Source properties and press Browse to paint a picture from your own computer instead.
Paint an SVG Into a WaterfallPaint an SVG into a waterfall display. The browser rasterizes the vector art at the size the file declares, so this paints 288 pixels wide like the PNG and JPEG examples; press Browse in the Image File Source properties to paint a picture from your own computer instead.
Paint a PNG Into a WaterfallPaint a PNG into a waterfall display. The image is fetched from this site; open the Image File Source properties and press Browse to paint a picture from your own computer instead.