Don't interact with the transform layer if the image is a single layer

src/engine/image.cpp

@@ -21,7 +21,6 @@
 #include "image.h"
 
 #include <algorithm>
-#include <cassert>
 #include <cmath>
 #include <cstddef>
 #include <cstdlib>
@@ -503,7 +502,10 @@ namespace fheroes2
         if ( !empty() ) {
             const size_t totalSize = static_cast<size_t>( _width ) * _height;
             memset( image(), value, totalSize );
-            memset( transform(), static_cast<uint8_t>( 0 ), totalSize );
+
+            if ( !_singleLayer ) {
+                memset( transform(), static_cast<uint8_t>( 0 ), totalSize );
+            }
         }
     }
 
@@ -532,8 +534,11 @@ namespace fheroes2
         if ( !empty() ) {
             const size_t totalSize = static_cast<size_t>( _width ) * _height;
             memset( image(), static_cast<uint8_t>( 0 ), totalSize );
-            // Set the transform layer to skip all data.
-            memset( transform(), static_cast<uint8_t>( 1 ), totalSize );
+
+            if ( !_singleLayer ) {
+                // Set the transform layer to skip all data.
+                memset( transform(), static_cast<uint8_t>( 1 ), totalSize );
+            }
         }
     }
 
@@ -545,18 +550,18 @@ namespace fheroes2
             return;
         }
 
-        const size_t size = static_cast<size_t>( image._width ) * image._height * 2;
+        const size_t imageSize = static_cast<size_t>( image._width ) * image._height;
 
         _singleLayer = image._singleLayer;
 
         if ( image._width != _width || image._height != _height ) {
-            _data.reset( new uint8_t[size] );
+            _data.reset( new uint8_t[imageSize * 2] );
 
             _width = image._width;
             _height = image._height;
         }
 
-        memcpy( _data.get(), image._data.get(), size );
+        memcpy( _data.get(), image._data.get(), _singleLayer ? imageSize : imageSize * 2 );
     }
 
     Sprite::Sprite( const int32_t width_, const int32_t height_, const int32_t x_ /* = 0 */, const int32_t y_ /* = 0 */ )

src/engine/image.h

@@ -19,6 +19,7 @@
  ***************************************************************************/
 #pragma once
 
+#include <cassert>
 #include <cstdint>
 #include <memory>
 #include <utility>
@@ -63,11 +64,17 @@ namespace fheroes2
 
         uint8_t * transform()
         {
+            // Why do you want to get transform layer from the single-layer image?
+            assert( !_singleLayer );
+
             return _data.get() + width() * height();
         }
 
         const uint8_t * transform() const
         {
+            // Why do you want to get transform layer from the single-layer image?
+            assert( !_singleLayer );
+
             return _data.get() + width() * height();
         }