Optimize the export dialog by caching all of the blended frames

No more slowness when changing the export settings. The only setting that causes the frames to be blended again is changing the layers.

src/Autoload/Export.gd

@@ -46,6 +46,9 @@ var custom_exporter_generators := {}
 var current_tab := ExportTab.IMAGE
 ## All frames and their layers processed/blended into images
 var processed_images: Array[ProcessedImage] = []
+## Dictionary of [Frame] and [Image] that contains all of the blended frames.
+## Changes when [method cache_blended_frames] is called.
+var blended_frames := {}
 var export_json := false
 var split_layers := false
 var trim_sprite := false
@@ -137,6 +140,7 @@ func remove_custom_file_format(id: int) -> void:
 
 
 func external_export(project := Global.current_project) -> void:
+	cache_blended_frames(project)
 	process_data(project)
 	export_processed_images(true, Global.export_dialog, project)
 
@@ -149,6 +153,15 @@ func process_data(project := Global.current_project) -> void:
 			process_spritesheet(project)
 
 
+func cache_blended_frames(project := Global.current_project) -> void:
+	blended_frames.clear()
+	var frames := _calculate_frames(project)
+	for frame in frames:
+		var image := Image.create(project.size.x, project.size.y, false, Image.FORMAT_RGBA8)
+		_blend_layers(image, frame)
+		blended_frames[frame] = image
+
+
 func process_spritesheet(project := Global.current_project) -> void:
 	processed_images.clear()
 	# Range of frames determined by tags
@@ -252,7 +265,8 @@ func process_spritesheet(project := Global.current_project) -> void:
 				origin.y = project.size.y * tag_origins[0]
 				origin.x = 0
 				tag_origins[0] += 1
-		_blend_layers(whole_image, frame, origin)
+		whole_image.blend_rect(blended_frames[frame], Rect2i(Vector2i.ZERO, project.size), origin)
+		#_blend_layers(whole_image, frame, origin)
 
 	processed_images.append(ProcessedImage.new(whole_image, 0))
 
@@ -271,7 +285,7 @@ func process_animation(project := Global.current_project) -> void:
 				)
 		else:
 			var image := Image.create(project.size.x, project.size.y, false, Image.FORMAT_RGBA8)
-			_blend_layers(image, frame)
+			image.copy_from(blended_frames[frame])
 			if trim_sprite:
 				image = image.get_region(image.get_used_rect())
 			var duration := frame.duration * (1.0 / project.fps)

src/UI/Dialogs/ExportDialog.gd

@@ -290,6 +290,7 @@ func _on_ExportDialog_about_to_show() -> void:
 	path_dialog_popup.current_dir = project.export_directory_path
 	file_line_edit.text = project.file_name
 	file_format_options.selected = project.file_format
+	Export.cache_blended_frames()
 	show_tab()
 
 	# Set the size of the preview checker
@@ -472,6 +473,7 @@ func _on_Frames_item_selected(id: int) -> void:
 
 func _on_Layers_item_selected(id: int) -> void:
 	Export.export_layers = id
+	Export.cache_blended_frames()
 	Export.process_data()
 	set_preview()
 

src/UI/Dialogs/ExportDialog.tscn

@@ -82,8 +82,8 @@ mouse_default_cursor_shape = 2
 selected = 0
 item_count = 4
 popup/item_0/text = "Columns"
-popup/item_0/id = 1
 popup/item_1/text = "Rows"
+popup/item_1/id = 1
 popup/item_2/text = "Tags by column"
 popup/item_2/id = 2
 popup/item_3/text = "Tags by row"