Fill a panorama's border with MI-GAN: mirrored context, coarse to fine, a feathered seam

dr_pano::fill owns everything the model does not — which tiles, what
context, how to blend — behind an Inpainter trait, and dr_pano::migan is
that trait over the shipped generator on the inference engine.

The known content is mirrored across the coverage edge into the hole and
a 256-px ring, the nearest 48 px folded, so the model interpolates between
real and mirrored sky rather than extrapolating into nothing. A coarse
pass at a quarter decides the structure with the whole border in a few
tiles; fine passes in 96-px bands from the edge outward texture it; the
seam is blended over a feather inside the real edge. Every knob is a
Params field, and an Observer hears each stage for whoever is looking at
why a fill went wrong.

core/dr-pano/src/lib.rs

@@ -35,10 +35,13 @@
 pub mod align;
 pub mod bundle;
 pub mod features;
+pub mod fill;
 pub mod homography;
 pub mod image;
 pub mod linalg;
 pub mod matching;
+#[cfg(feature = "xfeat")]
+pub mod migan;
 pub mod projection;
 #[cfg(feature = "xfeat")]
 pub mod xfeat;
@@ -46,6 +49,7 @@ pub mod xfeat;
 pub use align::{align, AlignOptions, Alignment, Link, Unaligned};
 pub use bundle::Cameras;
 pub use features::{Features, Keypoint};
+pub use fill::{fill_border, Inpainter, Observer, Params as FillParams};
 pub use image::Gray;
 pub use projection::Projection;
 
@@ -64,6 +68,13 @@ pub enum PanoError {
     Inference(#[source] ort::Error),
 }
 
+#[cfg(feature = "xfeat")]
+impl From<ort::Error> for PanoError {
+    fn from(e: ort::Error) -> Self {
+        PanoError::Inference(e)
+    }
+}
+
 #[cfg(feature = "xfeat")]
 impl From<dr_inference_engine::Error> for PanoError {
     fn from(e: dr_inference_engine::Error) -> Self {