How to use it
- Upload a PNG. Transparency is flattened onto white before encoding.
- Check the preview showing which areas will be lifted.
- Download the Ultra HDR JPEG.
What it looks like on an HDR screen
Simulated. On the screen you are reading this on, both halves are identical — an ordinary display has no extra brightness to give. This is how the difference reads on an HDR display.
What the converter actually builds
Both images above are real output from this converter, not an illustration. White areas of the gain map are the ones an HDR screen brightens; black areas stay exactly as they were.
Frequently asked questions
Why is the output a JPEG?
The Ultra HDR specification defines a JPEG container with a second image and metadata inside it. PNG has no equivalent structure, so there is nowhere to put the gain map.
What happens to transparency?
An alpha channel is composited onto a white background first, because JPEG cannot store transparency. If you need the transparent version, keep your PNG alongside the converted file.
Is a PNG a better source than a JPEG?
Usually yes. A PNG has not been through lossy compression, so there are no block artefacts near edges for the gain map to make more visible.
Does this work for screenshots and renders?
That is where it works best. Synthetic images have clean, well-defined highlights, and a gain map has no noise to amplify.