- fix tiled image reading

src/decoder/image.rs

@@ -36,6 +36,9 @@ impl TileAttributes {
     pub fn tiles_down(&self) -> usize {
         self.image_height.div_ceil(self.tile_length)
     }
+    pub fn tiles_per_plane(&self) -> usize {
+        self.tiles_across() * self.tiles_down()
+    }
     fn padding_right(&self) -> usize {
         (self.tile_width - self.image_width % self.tile_width) % self.tile_width
     }
@@ -1016,7 +1019,15 @@ impl Image {
             }
             ChunkType::Tile => {
                 let tile_attrs = self.tile_attributes.as_ref().unwrap();
-                let (padding_right, padding_down) = tile_attrs.get_padding(chunk_index as usize);
+                // The chunk index counts the tiles of all planes, but the tile grid repeats per
+                // plane, so only the position within the plane decides the padding.
+                let tiles_per_plane = tile_attrs.tiles_per_plane();
+                let tile = if tiles_per_plane == 0 {
+                    0
+                } else {
+                    chunk_index as usize % tiles_per_plane
+                };
+                let (padding_right, padding_down) = tile_attrs.get_padding(tile);
 
                 let tile_width = tile_attrs.tile_width - padding_right;
                 let tile_length = tile_attrs.tile_length - padding_down;