AVIFGAINMAPUTIL(1)

NAME
avifgainmaputil - Tool to manipulate AVIF images with HDR gain maps

SYNOPSIS
avifgainmaputil <command> [options] [arguments...]

DESCRIPTION

  Available commands:

help
    Print a command's usage

combine
    Create an AVIF image with a gain map from a base image and an alternate image

convert
    Convert a JPEG with a gain map to AVIF

tonemap
    Tone map an AVIF image that has a gain map to a given HDR headroom (how much brighter the display can go compared to SDR white)

swapbase
    Swap the base and alternate images (e.g. if the base image is SDR and the alternate is HDR, makes the base HDR)

extractgainmap
    Save the gain map of an AVIF file as an image

printmetadata
    Print the metadata of the gain map of an AVIF file

  General concepts:

    Gain maps allow creating HDR (High Dynamic Range) images that look good on any display, including SDR (Standard Dynamic Range) displays. Images with gain maps are also backward compatible with viewers that do not support gain maps.

    An image with a gain map consists of a "base image", and a "gain map image". The gain map image contains information used to "tone map" the base image, in order to adapt it to displays with different HDR capabilities. Fully applying the gain map results in a different image called the "alternate image". The gain map can also be applied partially, giving a result in between the base image and the alternate image.

    Typically, either the base image or the alternate image is SDR, and the other one is HDR. Both images have a target "HDR headroom" that they are meant to be displayed on. The HDR headroom is the ratio between the maximum brightness of white that the display can produce, and the standard SDR white brightness. This value is usually expressed in log2. An SDR display has an HDR headroom of 0. An HDR display with a headroom of 1 can produce white that is twice as bright as SDR white.

    Viewers that support gain maps will show the base image, or the alternate image, or something in between, depending on the display's current HDR headroom and the target headroom of the base image and alternate image. Viewers that do not support gain maps will always show the base image.

SEE ALSO
avifenc(1), avifdec(1)