How a FLIR radiometric JPG becomes temperature data — and the open-source tools that do it.
A FLIR camera saves an ordinary-looking JPG, but embedded inside it is a block of raw radiometric data plus the calibration constants needed to turn that data into temperatures. The original TrEnCh-IR website ran this conversion automatically on an Azure Function app. This static site instead documents the pipeline and points you to the open-source tools — primarily those by Glenn Tattersall — that you can run yourself to reproduce every output the live site generated.
Read the FLIR calibration parameters (Planck constants, emissivity, reflected temperature, atmospheric terms) and any GPS tags from the JPG with ExifTool.
Extract the embedded raw thermal data stream (a 16-bit image) and, if present, the embedded visible/digital photo.
Apply the Planck/radiance equations to convert each raw 16-bit value into a surface temperature in degrees Celsius.
Render the temperature matrix with ironbow, rainbow, and greyscale palettes, and export raw data + parameters for further analysis.
Temperature color palettes produced
All maintained by Glenn Tattersall (gtatters) on GitHub. Pick the one that fits your workflow — R, ImageJ, or the command line.
The core R package for working with radiometric thermal image files: import FLIR data, apply the raw-to-temperature conversion, and analyze and visualize temperature matrices. The recommended starting point for an R-based workflow.
ImageJ/Fiji functions and macros for opening FLIR files, converting to temperature, and measuring regions of interest interactively — ideal if you prefer a point-and-click GUI over scripting.
Command-line tools for batch-converting FLIR thermal image files. Useful for scripting bulk conversions of large image sets outside of R or ImageJ.
Focused routines for converting FLIR JPG files, extracting the embedded raw data and calibration parameters needed for temperature conversion.
Utilities geared toward FLIR ONE camera JPGs, handling their particular embedded data layout.
Reference data files comparing temperature calculations against thermal-imaging software, useful for validating your own conversion results.
Phil Harvey's ExifTool is the underlying utility these packages call to read FLIR metadata and extract the embedded raw thermal and visible images. Install it first.