libavif does not decode `iovl` overlay images

[farindk]

libavif currently does not decode iovl derived images. Here is an example file.

Is there any plan to support this? I have an application that would depend on showing overlay images correctly in Chrome.

[y-guyon]

Thank you for filing this issue.

Could you share more details on the use case please?

[farindk]

Think about image editors that allow to draw annotations on the image. Currently, one needs a custom file format if we want to exchange editable images (e.g. in order to move the annotations on the image). Those proprietary file formats obviously cannot be displayed in any standard software. So the user needs

• the proprietary file that can be edited, and
• an exported image that he can use on the web or in any other software.

With an HEIF overlay, we can put the annotation graphics into the overlay, keep the original image as the background image, and put the vector drawing data-structures in a custom box. Thus, we have a file that is editable and at the same time can be processed in standard software and shown on the web.

Since such images are currently not supported in Chrome, the user has to handle that pair of files and also a web-application has to work with two different file types instead of one.