Add a transform method to DrawingAlgos

Can be used as a general method to apply rotation and skewing. It does not handle scaling though, and I am not sure if it should.

src/Autoload/DrawingAlgos.gd

@@ -1,5 +1,6 @@
 extends Node
 
+enum RotationAlgorithm { ROTXEL_SMEAR, CLEANEDGE, OMNISCALE, NNS, NN, ROTXEL, URD }
 enum GradientDirection { TOP, BOTTOM, LEFT, RIGHT }
 ## Continuation from Image.Interpolation
 enum Interpolation { SCALE3X = 5, CLEANEDGE = 6, OMNISCALE = 7 }
@@ -14,6 +15,8 @@ var omniscale_shader: Shader:
 		if omniscale_shader == null:
 			omniscale_shader = load("res://src/Shaders/Effects/Rotation/OmniScale.gdshader")
 		return omniscale_shader
+var rotxel_shader := preload("res://src/Shaders/Effects/Rotation/SmearRotxel.gdshader")
+var nn_shader := preload("res://src/Shaders/Effects/Rotation/NearestNeighbour.gdshader")
 
 
 ## Blends canvas layers into passed image starting from the origin position
@@ -270,6 +273,41 @@ func scale_3x(sprite: Image, tol := 0.196078) -> Image:
 	return scaled
 
 
+func transform(
+	image: Image,
+	params: Dictionary,
+	algorithm: RotationAlgorithm,
+	project := Global.current_project
+) -> void:
+	var pivot: Vector2 = params.get("pivot", image.get_size() / 2)
+	if type_is_shader(algorithm):
+		params["pivot"] = pivot / Vector2(image.get_size())
+		var shader := rotxel_shader
+		match algorithm:
+			RotationAlgorithm.CLEANEDGE:
+				shader = clean_edge_shader
+			RotationAlgorithm.OMNISCALE:
+				shader = omniscale_shader
+			RotationAlgorithm.NNS:
+				shader = nn_shader
+		var gen := ShaderImageEffect.new()
+		gen.generate_image(image, shader, params, project.size)
+	else:
+		var transformation_matrix: Transform2D = params.get("transformation_matrix", Transform2D())
+		var angle := transformation_matrix.get_rotation()
+		match algorithm:
+			RotationAlgorithm.ROTXEL:
+				rotxel(image, angle, pivot)
+			RotationAlgorithm.NN:
+				nn_rotate(image, angle, pivot)
+			RotationAlgorithm.URD:
+				fake_rotsprite(image, angle, pivot)
+
+
+func type_is_shader(algorithm: RotationAlgorithm) -> bool:
+	return algorithm <= RotationAlgorithm.NNS
+
+
 func rotxel(sprite: Image, angle: float, pivot: Vector2) -> void:
 	if is_zero_approx(angle) or is_equal_approx(angle, TAU):
 		return

src/UI/Canvas/Selection.gd

@@ -46,6 +46,7 @@ var undo_data: Dictionary
 var gizmos: Array[Gizmo] = []
 var dragged_gizmo: Gizmo = null
 var angle := 0.0
+var rotation_algorithm := DrawingAlgos.RotationAlgorithm.NN
 var content_pivot := Vector2.ZERO
 var mouse_pos_on_gizmo_drag := Vector2.ZERO
 var resize_keep_ratio := false
@@ -405,7 +406,9 @@ func resize_selection() -> void:
 				)
 		else:
 			content_pivot = original_big_bounding_rectangle.size / 2.0
-			DrawingAlgos.nn_rotate(preview_image, angle, content_pivot)
+			var transformation_matrix := Transform2D(angle, Vector2.ZERO)
+			var params := {"transformation_matrix": transformation_matrix, "pivot": content_pivot}
+			DrawingAlgos.transform(preview_image, params, rotation_algorithm)
 			preview_image.resize(size.x, size.y, Image.INTERPOLATE_NEAREST)
 			if temp_rect.size.x < 0:
 				preview_image.flip_x()
@@ -416,7 +419,9 @@ func resize_selection() -> void:
 	Global.current_project.selection_map.copy_from(original_bitmap)
 
 	var bitmap_pivot := original_big_bounding_rectangle.get_center()
-	DrawingAlgos.nn_rotate(Global.current_project.selection_map, angle, bitmap_pivot)
+	var bitmap_matrix := Transform2D(angle, Vector2.ZERO)
+	var bitmap_params := {"transformation_matrix": bitmap_matrix, "pivot": bitmap_pivot}
+	DrawingAlgos.transform(Global.current_project.selection_map, bitmap_params, rotation_algorithm)
 	Global.current_project.selection_map.resize_bitmap_values(
 		Global.current_project, size, temp_rect.size.x < 0, temp_rect.size.y < 0
 	)
@@ -552,7 +557,11 @@ func transform_content_confirm() -> void:
 				src.crop(preview_image.get_width(), preview_image.get_height())
 				tilemap.apply_resizing_to_image(src, selected_cells, big_bounding_rectangle)
 			else:
-				DrawingAlgos.nn_rotate(src, angle, content_pivot)
+				var transformation_matrix := Transform2D(angle, Vector2.ZERO)
+				var params := {
+					"transformation_matrix": transformation_matrix, "pivot": content_pivot
+				}
+				DrawingAlgos.transform(src, params, rotation_algorithm)
 				src.resize(
 					preview_image.get_width(), preview_image.get_height(), Image.INTERPOLATE_NEAREST
 				)

src/UI/Dialogs/ImageEffects/RotateImage.gd

@@ -80,7 +80,7 @@ func _calculate_pivot() -> void:
 func commit_action(cel: Image, project := Global.current_project) -> void:
 	var angle := deg_to_rad(animate_panel.get_animated_value(commit_idx, Animate.ANGLE))
 	var init_angle := deg_to_rad(animate_panel.get_animated_value(commit_idx, Animate.INIT_ANGLE))
-
+	var rotation_algorithm := type_option_button.get_selected_id()
 	var selection_tex: ImageTexture
 	var image := Image.new()
 	image.copy_from(cel)
@@ -88,7 +88,7 @@ func commit_action(cel: Image, project := Global.current_project) -> void:
 		var selection := project.selection_map.return_cropped_copy(project.size)
 		selection_tex = ImageTexture.create_from_image(selection)
 
-		if !_type_is_shader():
+		if not DrawingAlgos.type_is_shader(rotation_algorithm):
 			var blank := project.new_empty_image()
 			cel.blit_rect_mask(
 				blank, selection, Rect2i(Vector2i.ZERO, cel.get_size()), Vector2i.ZERO
@@ -97,41 +97,26 @@ func commit_action(cel: Image, project := Global.current_project) -> void:
 			image.blit_rect_mask(
 				blank, selection, Rect2i(Vector2i.ZERO, image.get_size()), Vector2i.ZERO
 			)
-	if _type_is_shader():
-		var shader := rotxel_shader
+	var transformation_matrix := Transform2D(angle, Vector2.ZERO)
 	var params := {
-			"transformation_matrix": Transform2D(angle, Vector2.ZERO),
+		"transformation_matrix": transformation_matrix,
+		"pivot": pivot,
 		"selection_tex": selection_tex,
-			"pivot": pivot / Vector2(cel.get_size()),
+		"initial_angle": init_angle,
+		"ending_angle": angle,
+		"tolerance": tolerance_slider.value,
 		"preview": true
 	}
-		match type_option_button.get_selected_id():
-			ROTXEL_SMEAR:
-				params["ending_angle"] = angle
-				params["initial_angle"] = init_angle
-				params["tolerance"] = tolerance_slider.value
-			CLEANEDGE:
-				shader = DrawingAlgos.clean_edge_shader
-			OMNISCALE:
-				shader = DrawingAlgos.omniscale_shader
-			NNS:
-				shader = nn_shader
+	if DrawingAlgos.type_is_shader(rotation_algorithm):
 		if !has_been_confirmed:
+			params["pivot"] /= Vector2(cel.get_size())
 			for param in params:
 				preview.material.set_shader_parameter(param, params[param])
 		else:
 			params["preview"] = false
-			var gen := ShaderImageEffect.new()
-			gen.generate_image(cel, shader, params, project.size)
+			DrawingAlgos.transform(cel, params, rotation_algorithm, project)
 	else:
-		match type_option_button.get_selected_id():
-			ROTXEL:
-				DrawingAlgos.rotxel(image, angle, pivot)
-			NN:
-				DrawingAlgos.nn_rotate(image, angle, pivot)
-			URD:
-				DrawingAlgos.fake_rotsprite(image, angle, pivot)
-
+		DrawingAlgos.transform(image, params, rotation_algorithm, project)
 		if project.has_selection and selection_checkbox.button_pressed:
 			cel.blend_rect(image, Rect2i(Vector2i.ZERO, image.get_size()), Vector2i.ZERO)
 		else:
@@ -140,10 +125,6 @@ func commit_action(cel: Image, project := Global.current_project) -> void:
 			cel.convert_rgb_to_indexed()
 
 
-func _type_is_shader() -> bool:
-	return type_option_button.get_selected_id() <= NNS
-
-
 func _on_TypeOptionButton_item_selected(_id: int) -> void:
 	match type_option_button.get_selected_id():
 		ROTXEL_SMEAR:

src/UI/Dialogs/ImageEffects/RotateImage.tscn

@@ -3,7 +3,7 @@
 [ext_resource type="Script" path="res://src/UI/Dialogs/ImageEffects/RotateImage.gd" id="1"]
 [ext_resource type="PackedScene" uid="uid://bybqhhayl5ay5" path="res://src/UI/Dialogs/ImageEffects/ImageEffectParent.tscn" id="2"]
 [ext_resource type="PackedScene" uid="uid://yjhp0ssng2mp" path="res://src/UI/Nodes/Sliders/ValueSlider.tscn" id="3"]
-[ext_resource type="PackedScene" path="res://src/UI/Nodes/Sliders/ValueSliderV2.tscn" id="4"]
+[ext_resource type="PackedScene" uid="uid://bbnqcxa20a5a5" path="res://src/UI/Nodes/Sliders/ValueSliderV2.tscn" id="4"]
 
 [node name="RotateImage" instance=ExtResource("2")]
 title = "Rotate Image"