I created a RAW to HDRI stacker in (mostly) Common Lisp

In plain words

This tool converts RAW camera images into HDR images written mostly in Common Lisp. It addresses limitations in existing HDR stacking software by offering batch processing capabilities, proper metadata preservation, and significantly faster performance than the creator's original Python version from 15 years ago. The new implementation leverages SIMD acceleration in SBCL for speed improvements while maintaining careful memory management.

written from the facts on this page · September 2026

From the sources

rawtohdri Converts bracketed camera raw files directly to an OpenEXR format HDRI. - IBL-tools/rawtohdri

rawtohdri takes a bracketed set of camera raw files, converts them directly to linear light images and stacks them into an HDR image saved in OpenEXR format (HALF or FLOAT) with ZIP compression. It has minimal external dependencies requiring only LibRaw, which most distros include in their package systems. (All Lisp dependencies are available via Quicklisp so that part is easy). rawtohdri's main claims to fame are its speed and efficiency. It features thread-parallel conversion of raw files and the ability to convert the integer output from LibRaw (16 bit integers) to floating point HDRIs in-memory using the least amount of memory possible (one buffer for the final composition) with…from github.com

In the maker’s words, at launch

This is an upgrade of a tool I created 15 years ago in Python to learn OOP and solve some inadequacies in the HDR stacking tools I could find at the time. The problem was, none of them were really "batch friendly". None of them properly preserved the metadata I wanted them to stuff into the output file. There were…

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