Adding a gain map to HEIC images using macOS Sequoia?

Thanks for your reply. I was hoping to find a single app or a step-by-step guide of some sort.

I prefer the HEIC format especially for 10-bit HDR images. Several R-series Canon cameras support HDR PQ (Perception Quantization transfer curve). I configure the camera to capture both (compressed) RAW and HEIC images. I typically upload only the HEIF (in fact, I deliberately lower the resolution from 45 to about 20 megapixels to reduce size) to the computer for editing and organizing using Photos. The higher resolution (and 12-bit) RAW files are still available on the camera should they be needed (e.g. a large print of a highly cropped image).

I would like to retain the HEIC format but be able to take advantage of gain maps similar to JPEG-XL. I am also hoping that Canon will support JEPG-XL at some point in the future.

- Pie Lover

Here's a recent Substack article that discusses Gain Maps: Process Apple Gain Map: The ImageIO & the Core Image approaches.

Interestingly, it mentions that " ...when editing images in the Photos app, Apple also preserves the Gain Map in the final images". I believe that the same is true from Preview exports.

- Pie Lover

Thanks for the advice. I had downloaded the trial version of Pixelmator Pro but, in the end, didn't install it.

Gimp has support for converting images to JPEG-XL but, when I tried it with HEIC HDR PQ, the source file colour space did not seem to be interpreted correctly.

I am realizing that HEIC is not a very popular format (except for iPhone perhaps). As you suggest, many photographers prefer editing directly using their camera's RAW format. For my part, I like shooting HEIF+RAW. This approach provides the option to edit the RAW file if needed. I also think that HDR PQ is a good way to get started with HDR. Unfortunately, the HDR PQ variant isn't well supported by macOS (consumer) apps.

I'm curious to see how Apple integrates Pixelator Pro. Perhaps they'll follow the Final Cut Pro model.

- Pie Lover

P.S. Here's a YouTube overview of JPEG-XL (What It Is And Why You Should Care)

I was finally able to create a JPEG-XL file using GIMP (V2.10.38) but was limited to 8-bit instead of the 10-bit captured in the original HDR PQ HEIC file.

- Pie Lover