Supernova
Back to HDR PNG Converter
✦ § 00 · Overview

How HDR PNG Conversion Works

Supernova converts standard images into HDR PNGs that glow on HDR displays. On compatible browsers/displays, preview shows the converted HDR output directly; otherwise it falls back to fast SDR preview while the final download stays full HDR PQ.

§ 01 · The pipeline

The Pipeline

1. Decode your image into raw 8-bit RGBA pixels via Canvas
2. Live preview path: on compatible browsers/displays, render a downscaled converted HDR PNG; otherwise use a fast SDR approximation for responsive updates
3. Export path: apply look controls in linear light, remap boost to HDR luminance, then PQ-encode to 16-bit BT.2020
4. Wrap in a PNG with HDR metadata chunks (cICP, cHRM, iCCP)
§ 02 · Controls

The Controls

  • Boost. HDR export brightness. 1.0≈100 nits, 4.0≈1600 nits, 10≈10000 nits in the final PNG.
  • Saturation. Primary color intensity, shown in the main panel for quick edits.
  • Fine tune. Exposure, Temperature, Tint, Gamma, Contrast, Highlight Roll-off, Shadow Lift, Vibrance.
  • Advanced. Blacks, Whites, Clarity, Highlight Saturation, Shadow Glow. Tucked behind a disclosure for visitors who want them.
  • Preview. Uses the converted HDR PNG when the browser and display support it, with automatic SDR fallback otherwise.
§ 03 · Transfer

What is PQ?

PQ (Perceptual Quantizer) is the transfer function behind HDR10 and Dolby Vision. Unlike gamma (~2.2) which tops out at 100 nits, PQ maps luminance up to 10,000 nits.

Its curve allocates more precision to dim regions where our eyes are most sensitive: far more efficient than gamma for HDR's wide brightness range.

γ 2.2PQLinear lightEncoded signal0101
§ 04 · Metadata

The Metadata

A valid HDR PNG needs metadata so the display knows how to interpret the pixels:

  • cICP. Declares BT.2020 primaries + PQ transfer. The primary HDR signal.
  • cHRM. BT.2020 chromaticity coordinates as fallback.
  • iCCP. Embedded ICC profile for broadest compatibility. Triggers EDR on macOS.
RGBBT.2020sRGBxy
§ 05 · Support

Compatibility

Requires an HDR display and a supported browser. On SDR displays, the image renders as a normal PNG.

ChromecICPFull HDR rendering
EdgecICPFull HDR rendering
SafariICC / EDRmacOS only
Firefoxn/aNo extended brightness
§ 06 · Privacy

Privacy

Conversion runs in your tab. Images stay on your device.

§ 07 · Guides

Related Guides