We included ImageMagick in the Bitnami CanvasLMS stack some weeks ago. From the version 2017.10.07.18-0 on, that component is included in all the Bitnami CanvasLMS deployments so you don't need to install anything. In case you are using a previous version, you can install it by using the system packages.
As @tomasp mentioned, there are some issues that are related with the application. We suggest you ask in the Github repository of the application to get more information about the issue and possible approaches to fix it.