Render: plain satin with no distance on an image is not drawn

Both shifted copies are the same at distance 0, so the coverage mask is empty. The effect is now skipped before the image is drawn offscreen and scanned.

crates/render/src/fx.rs

@@ -329,8 +329,10 @@ impl Renderer {
             }
         }
         // Satin: the shape shifted both ways along the angle, blurred, where exactly one covers.
-        // With a graphic, the shape is what the object paints, as for the inner shadow.
+        // With a graphic, the shape is what the object paints, as for the inner shadow. Plain
+        // satin on a graphic with no distance compares two equal copies and is not drawn.
         if e.satin.on
+            && !(painted.is_some() && !e.satin.invert && e.satin.distance == 0.0)
             && let Some(c) = doc.resolve_color(&e.satin.color, 1.0)
         {
             let st = &e.satin;