From f553646d70fba8e265d436103a73520eb7adec8c Mon Sep 17 00:00:00 2001
From: David Michael Barr <b@rr-dav.id.au>
Date: Thu, 8 Jul 2021 13:39:59 +0900
Subject: [PATCH] Initialise residual when less than the transform width is
 visible

The input stride for forward transforms did not match the output
stride of residual computation in this case. Extend the residual
stride to the transform width and zero the non-visible portion.
Fixes #2662. Fixes #2757.
---
 src/encoder.rs | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/encoder.rs b/src/encoder.rs
index 564d78d7e..1ccf8c831 100644
--- a/src/encoder.rs
+++ b/src/encoder.rs
@@ -1209,12 +1209,20 @@ pub fn encode_tx_block<T: Pixel, W: Writer>(
       residual,
       &ts.input_tile.planes[p].subregion(area),
       &rec.subregion(area),
-      visible_tx_w,
+      tx_size.width(),
       visible_tx_h,
     );
+    if visible_tx_w < tx_size.width() {
+      for row in residual.chunks_mut(tx_size.width()).take(visible_tx_h) {
+        for a in &mut row[visible_tx_w..] {
+          *a = 0;
+        }
+      }
+    }
   }
-  let visible_area = visible_tx_w * visible_tx_h;
-  for a in residual[visible_area..].iter_mut() {
+  let initialized_area =
+    if visible_tx_w == 0 { 0 } else { tx_size.width() * visible_tx_h };
+  for a in residual[initialized_area..].iter_mut() {
     *a = 0;
   }