HDR to QOI Converter
Convert HDR to QOI in your browser. HDR files usually come from HDRI environment maps, 360° panoramas and lighting simulation; QOI is the better fit for fast lossless storage in games and tools. You get a lossless RGBA QOI file. Nothing is uploaded.
- Processed locally
- No upload, no wait
- No sign-up
- No watermark
Drop images here
or choose files · paste with Ctrl/⌘ V
HDR expected · other image formats also work
How to use HDR to QOI
- 1
Add your HDR files: drop them here, choose them, or paste from the clipboard.
- 2
There is nothing to tune: the QOI is written losslessly. Resizing and rotating are under More options if you need them.
- 3
Click Convert. Each file is decoded and encoded in a background thread on this device.
- 4
Download the .qoi files one at a time or together as a ZIP.
Why use Aback Images for hdr to qoi
Where the QOI goes next
QOI opens in game engines, GIMP 3, ImageMagick, XnView MP and many small libraries.
QOI next to HDR
Both sides are lossless, so the size depends on how well the QOI encoder handles this picture compared with the HDR's run-length encoded RGBE scanlines.
Written without a lossy pass
The QOI is written losslessly, so the pixels decoded from the HDR arrive unchanged, apart from precision beyond 8 bits per channel.
Processed on your device
Your images are decoded, edited and encoded inside this browser tab by Web Workers. Nothing is uploaded to a server.
HDR vs QOI
What changes from HDR to QOI
Encoding: the HDR uses run-length encoded RGBE scanlines; QOI uses lossless, byte-aligned run, index, difference and literal codes, and the download is a lossless RGBA QOI file.
Bit depth: an 8-bit mantissa per channel sharing an 8-bit exponent (RGBE), 32 bits per pixel in the HDR; QOI allows 8 bits per channel, and the QOI written here has 8 bits per channel. The high dynamic range is mapped to 8 bits per channel, and values above white clip.
Colour: linear RGB (or XYZ in the XYZE variant) in the HDR; QOI supports RGB or RGBA, tagged sRGB or linear, written here as 8-bit sRGB.
Metadata: the HDR can carry a text header with FORMAT, EXPOSURE and optional comments; QOI can carry none: a 14-byte header holds only size, channels and colour space, but nothing is copied across.
About HDR
Radiance .hdr stores high dynamic range light values, widely used for 3D environment maps and HDRI lighting.
A Radiance file starts with '#?RADIANCE' (or '#?RGBE'), text lines such as FORMAT=32-bit_rle_rgbe and EXPOSURE, a blank line, a resolution line like '-Y 2048 +X 4096', then the scanlines.
HDR files usually come from HDRI environment maps, 360° panoramas and lighting simulation.
About QOI
QOI is a modern lossless format that encodes 20-50 times faster than PNG with similar file sizes. It is popular in games and tools that value speed and simplicity.
A QOI file is a 14-byte header ('qoif', width, height, channels, colour space), a stream of chunks that each encode a run, an index into 64 recently seen colours, a small difference from the previous pixel or a literal value, and an 8-byte end marker.
When converting HDR to QOI makes sense
QOI is the better choice for fast lossless storage in games and tools, while HDR suits 3D lighting and environment maps.
QOI strengths: Extremely fast lossless encode and decode; Simple, open spec. Drawbacks to weigh: Not supported by browsers or mainstream apps.
Limitations
- Light values above 1.0 are clipped rather than tone-mapped, so the sun and bright sky turn flat white.
- Environment maps are 2:1 equirectangular panoramas, so the picture looks stretched near the top and bottom, as it should.
- Files in the XYZE variant cannot be read here; RGBE files, the common kind, can.
- Browsers and most mainstream apps cannot open QOI; it is meant for games and tools that read it directly.
- QOI files are usually close to PNG in size but much faster to encode and decode.
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Frequently asked questions
Does converting HDR to QOI lose quality?
QOI is written losslessly, so the pixels are stored exactly as decoded. The high dynamic range is mapped to 8 bits per channel, and values above white clip.
Which apps open QOI files?
Game engines, GIMP 3, ImageMagick, XnView MP and many small libraries. It does not open in web browsers.
Are my images uploaded anywhere?
No. Processing happens inside your browser with WebAssembly and Web Workers. The site only downloads the app code and codecs; your files never leave your device. You can confirm this with the live upload counter on the tool, or in your browser's network panel.
Can I process many files at once?
Yes. Drop a whole selection or folder. Files are processed in parallel on several worker threads, each result can be downloaded on its own, and everything can be saved as one ZIP.
Is it free? Is there a file limit or watermark?
It is free with no account, no watermark and no daily limit. The only limit is your device's memory: very large images (over roughly 100 megapixels) may be refused to keep the tab from crashing.