[lua] Fix crash when saving tilemap's cel image (fix #4069)

src/app/script/image_class.cpp

@@ -454,10 +454,29 @@ int Image_saveAs(lua_State* L)
     return luaL_error(L, "script doesn't have access to write file %s",
                       absFn.c_str());
 
-  std::unique_ptr<Sprite> sprite(Sprite::MakeStdSprite(img->spec(), 256));
-
+  std::unique_ptr<Sprite> sprite;
   std::vector<ImageRef> oneImage;
-  sprite->getImages(oneImage);
+  // If we are saving a tilemap's image, we create a sprite with a tilemap layer
+  // and the cel's layer tileset.
+  // TODO: Consider the possibility to add a "tileset" parameter to
+  // Image:saveAs{}.
+  if (cel && cel->layer()->isTilemap()) {
+    auto tileset = static_cast<LayerTilemap*>(cel->layer())->tileset();
+    auto spec = cel->sprite()->spec();
+    // Use the correct final image size, not the sprite size.
+    spec.setSize(tileset->grid().tilemapSizeToCanvas(img->spec().size()));
+    sprite.reset(Sprite::MakeStdTilemapSpriteWithTileset(spec,
+                                                         img->spec(),
+                                                         *tileset,
+                                                         256));
+    sprite->getTilemapsByTileset(sprite->tilesets()->get(0), oneImage);
+  }
+  // Create a standard sprite otherwise
+  else {
+    sprite.reset(Sprite::MakeStdSprite(img->spec(), 256));
+    sprite->getImages(oneImage);
+  }
+
   ASSERT(oneImage.size() == 1);
   if (!oneImage.empty())
     copy_image(oneImage.front().get(), img);

src/doc/sprite.cpp

@@ -29,6 +29,7 @@
 
 #include <algorithm>
 #include <cstring>
+#include <functional>
 #include <memory>
 #include <vector>
 
@@ -119,23 +120,18 @@ Sprite::~Sprite()
   }
 }
 
-// static
-Sprite* Sprite::MakeStdSprite(const ImageSpec& spec,
-                              const int ncolors,
-                              const ImageBufferPtr& imageBuf)
+static Sprite* makeSprite(const ImageSpec& spec,
+                          const ImageRef& image,
+                          std::function<std::unique_ptr<LayerImage>(Sprite* sprite)> makeLayer,
+                          const int ncolors,
+                          const ImageBufferPtr& imageBuf)
 {
   // Create the sprite.
-  std::unique_ptr<Sprite> sprite(new Sprite(spec, ncolors));
+  std::unique_ptr<Sprite> sprite = std::make_unique<Sprite>(spec, ncolors);
   sprite->setTotalFrames(frame_t(1));
-
-  // Create the main image.
-  ImageRef image(Image::create(spec, imageBuf));
-  clear_image(image.get(), 0);
-
-  // Create the first transparent layer.
+  // Create the first layer.
   {
-    std::unique_ptr<LayerImage> layer(new LayerImage(sprite.get()));
-    layer->setName("Layer 1");
+    std::unique_ptr<LayerImage> layer = makeLayer(sprite.get());
 
     // Create the cel.
     {
@@ -154,6 +150,50 @@ Sprite* Sprite::MakeStdSprite(const ImageSpec& spec,
   return sprite.release();
 }
 
+// static
+Sprite* Sprite::MakeStdSprite(const ImageSpec& spec,
+                              const int ncolors,
+                              const ImageBufferPtr& imageBuf)
+{
+  // Create the main image.
+  ImageRef image(Image::create(spec, imageBuf));
+  clear_image(image.get(), 0);
+
+  auto makeLayer = [](Sprite* sprite) {
+                     // Create a transparent layer.
+                     auto layer = std::make_unique<LayerImage>(sprite);
+                     layer->setName("Layer 1");
+                     return layer;
+                   };
+  return makeSprite(spec, image, makeLayer, ncolors, imageBuf);
+}
+
+// static
+Sprite* Sprite::MakeStdTilemapSpriteWithTileset(const ImageSpec& spec,
+                                                const ImageSpec& tilemapspec,
+                                                const Tileset& tileset,
+                                                const int ncolors,
+                                                const ImageBufferPtr& imageBuf)
+{
+  ASSERT(spec.colorMode() != ColorMode::TILEMAP);
+  ASSERT(tilemapspec.colorMode() == ColorMode::TILEMAP);
+
+  ImageRef image(Image::create(tilemapspec, imageBuf));
+  clear_image(image.get(), 0);
+
+  auto makeLayer = [&tileset](Sprite* sprite) {
+                     // Create a tilemap layer.
+                     // We first need to add the tileset to the sprite.
+                     sprite->tilesets()->add(
+                       Tileset::MakeCopyCopyingImages(&tileset));
+
+                     auto layer = std::make_unique<LayerTilemap>(sprite, 0);
+                     layer->setName("Tilemap 1");
+                     return layer;
+                   };
+  return makeSprite(spec, image, makeLayer, ncolors, imageBuf);
+}
+
 //////////////////////////////////////////////////////////////////////
 // Main properties
 

src/doc/sprite.h

@@ -73,6 +73,14 @@ namespace doc {
     static Sprite* MakeStdSprite(const ImageSpec& spec,
                                  const int ncolors = 256,
                                  const ImageBufferPtr& imageBuf = ImageBufferPtr());
+    // Creates a new sprite with one tilemap layer and one cel
+    // with a tilemap's image of the size specified by tilemapspec and the
+    // given tileset.
+    static Sprite* MakeStdTilemapSpriteWithTileset(const ImageSpec& spec,
+                                  const ImageSpec& tilemapspec,
+                                  const Tileset& tileset,
+                                  const int ncolors = 256,
+                                  const ImageBufferPtr& imageBuf = ImageBufferPtr());
 
     ////////////////////////////////////////
     // Main properties

tests/scripts/image.lua

@@ -179,6 +179,29 @@ do
   end
 end
 
+-- Save image from a tilemap's cel
+do
+  local spr = Sprite{ fromFile="sprites/2x2tilemap2x2tile.aseprite" }
+  local tilemapImg = spr.layers[1].cels[1].image
+  local tileset = spr.layers[1].tileset
+  local tileSize = tileset.grid.tileSize
+  tilemapImg:saveAs("_test_save_tilemap_cel_image.png")
+
+  local img = Image{ fromFile="_test_save_tilemap_cel_image.png" }
+  assert(img.width == tilemapImg.width * tileSize.width)
+  assert(img.height == tilemapImg.height * tilemapImg.height)
+  for y=0,img.height-1 do
+    for x=0,img.width-1 do
+      local tmx = x // tileSize.w;
+      local tmy = y // tileSize.h;
+      local tileImg = tileset:getTile(tilemapImg:getPixel(tmx, tmy));
+      -- Compare each pixel of the saved image with each pixel of the
+      -- corresponding tile of the original sprite's tilemap.
+      assert(img:getPixel(x, y) == tileImg:getPixel(x % tileSize.w, y % tileSize.h))
+    end
+  end
+end
+
 -- Resize image
 do
   local a = Sprite(3, 2)

tests/sprites/README.md

@@ -33,3 +33,5 @@
 * `slices-moving.aseprite`: Indexed, 4x4, 1 linked cel in 4 frames,
   background layer, 1 slice with 4 keyframes (each keyframe with a
   different position/size).
+* `2x2tilemap2x2tile.aseprite`: RGB, 6x6, 2x2 tilemap layer, 5 tiles tileset,
+2x2 tile size, 1 frame.