Add imagemagick notes to docs for ReagentX#318

imessage-exporter/README.md

@@ -48,6 +48,7 @@ The [releases page](https://github.com/ReagentX/imessage-exporter/releases) prov
         Compatible will convert HEIC files to JPEG
         Efficient will copy files without converting anything
         If omitted, the default is `disabled`
+        ImageMagick is required to convert images on non-macOS platforms.
         
 -p, --db-path <path/to/source>
         Specify an optional custom path for the iMessage database location
@@ -142,6 +143,10 @@ imessage-exporter -f txt -o ~/export-2020 -s 2020-01-01 -e 2021-01-01 -a macOS
 
 ## Caveats
 
+### Cross-platform HEIC conversion
+
+[ImageMagick](https://imagemagick.org/index.php) is required to make exported images more compatible on non-macOS platforms.
+
 ### HTML Exports
 
 In HTML exports in Safari, when referencing files in-place, you must permit Safari to read from the local file system in the `Develop > Developer Settings...` menu:

imessage-exporter/src/app/options.rs

@@ -327,7 +327,7 @@ fn get_command() -> Command {
             Arg::new(OPTION_ATTACHMENT_MANAGER)
             .short('c')
             .long(OPTION_ATTACHMENT_MANAGER)
-            .help(format!("Specify an optional method to use when copying message attachments\nCompatible will convert HEIC files to JPEG\nEfficient will copy files without converting anything\nIf omitted, the default is `{}`\n", AttachmentManager::default()))
+            .help(format!("Specify an optional method to use when copying message attachments\nCompatible will convert HEIC files to JPEG\nEfficient will copy files without converting anything\nIf omitted, the default is `{}`\nImageMagick is required to convert images on non-macOS platforms.\n", AttachmentManager::default()))
             .display_order(2)
             .value_name(SUPPORTED_ATTACHMENT_MANAGER_MODES),
         )