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@@ -43,3 +43,9 @@ if b"ICC_PROFILE\0" == &app2_marker_data[0..12] {
 There's more in the `examples` directory.
 
 This crate requires Rust 1.18 or later. It's up to date with LCMS 2.8 (should work with 2.6 to 2.9).
+
+## Threads
+
+In LCMS all functions are in 2 flavors: global and `*THR()` functions. In this crate this is represented by having functions with `GlobalContext` and `ThreadContext`. Create profiles, transforms, etc. using `*_context()` constructors to give them their private coontext, which makes them sendable between threads (i.e. they're `Send`).
+
+`Transform` does not implement `Sync`, because LCMS2 has a thread-unsafe cache in the transform.