Heroku - how to enable gd on heroku php application?

Question

Heroku said:

The following built-in extensions have been built “shared” and can be enabled through composer.json (internal identifier names given in

Answer 1

Just adding GD as dependency (require) in composer does not load the extension GD. It just tells that this package needs gd enabled. "ext-gd" is just a virtual package, not existing for real.

you have to install it on your platform.

see here composer - platform-packages