Shader based rotation

src/Shaders/Rotation.shader

@@ -0,0 +1,57 @@
+shader_type canvas_item;
+
+uniform float angle;
+uniform sampler2D selection_tex;
+uniform vec2 selection_pivot;
+uniform vec2 selection_size;
+
+
+vec2 rotate(vec2 uv, vec2 pivot, float ratio) {
+	// Scale and center image
+	uv.x -= 0.5;
+	uv.x *= ratio;
+	uv.x += 0.5;
+
+	// Rotate image
+	uv -= pivot;
+	uv = vec2(cos(angle) * uv.x + sin(angle) * uv.y,
+				-sin(angle) * uv.x + cos(angle) * uv.y);
+	uv.x /= ratio;
+	uv += pivot;
+
+	return uv;
+}
+
+
+void fragment() {
+	vec4 original = texture(TEXTURE, UV);
+	float selection = texture(selection_tex, UV).a;
+
+	vec2 tex_size = 1.0 / TEXTURE_PIXEL_SIZE; // Texture size in real pixel coordinates
+	vec2 pixelated_uv = floor(UV * tex_size) / (tex_size - 1.0); // Pixelate UV to fit resolution
+	vec2 pivot = selection_pivot / tex_size; // Normalize pivot position
+	vec2 sel_size = selection_size / tex_size; // Normalize selection size
+	float ratio = tex_size.x / tex_size.y; // Resolution ratio
+
+	// Make a border to prevent stretching pixels on the edge
+	vec2 border_uv = rotate(pixelated_uv, pivot, ratio);
+	border_uv -= pivot - sel_size / 2.0; // Move the border to selection position
+	border_uv /= sel_size; // Set border size to selection size
+
+	// Center the border
+	border_uv -= 0.5;
+	border_uv *= 2.0;
+	border_uv = abs(border_uv);
+
+	float border = max(border_uv.x, border_uv.y); // This is a rectangular gradient
+	border = floor(border - TEXTURE_PIXEL_SIZE.x); // Turn the grad into a rectangle shape
+	border = 1.0 - clamp(border, 0.0, 1.0); // Invert the rectangle
+
+	// Mixing
+	vec4 rotated = texture(TEXTURE, rotate(pixelated_uv, pivot, ratio)); // Rotated image
+	rotated.a *= texture(selection_tex, rotate(pixelated_uv, pivot, ratio)).a; // Combine with rotated selection mask
+
+	COLOR.rgb = mix(original.rgb, rotated.rgb, rotated.a * border); // Mix original image and rotated
+	COLOR.a = mix(original.a, 0.0, selection); // Remove alpha on the selected area
+	COLOR.a = mix(COLOR.a, 1.0, rotated.a * border); // Combine alpha of original image and rotated
+}

src/UI/Dialogs/ImageEffects/RotateImage.gd

@@ -1,6 +1,9 @@
 extends ImageEffect
 
 var live_preview: bool = true
+var confirmed := false
+var shader: Shader = preload("res://src/Shaders/Rotation.shader")
+
 onready var type_option_button: OptionButton = $VBoxContainer/HBoxContainer2/TypeOptionButton
 onready var angle_hslider: HSlider = $VBoxContainer/AngleOptions/AngleHSlider
 onready var angle_spinbox: SpinBox = $VBoxContainer/AngleOptions/AngleSpinBox
@@ -12,6 +15,7 @@ func _ready() -> void:
 	type_option_button.add_item("Rotxel")
 	type_option_button.add_item("Upscale, Rotate and Downscale")
 	type_option_button.add_item("Nearest neighbour")
+	type_option_button.add_item("Nearest neighbour (Shader)")
 
 
 func set_nodes() -> void:
@@ -21,21 +25,27 @@ func set_nodes() -> void:
 
 
 func _about_to_show() -> void:
+	confirmed = false
 	._about_to_show()
 	wait_apply_timer.wait_time = wait_time_spinbox.value / 1000.0
 	angle_hslider.value = 0
 
 
 func commit_action(_cel: Image, _project: Project = Global.current_project) -> void:
 	var angle: float = deg2rad(angle_hslider.value)
-	# warning-ignore:integer_division
-	# warning-ignore:integer_division
+# warning-ignore:integer_division
+# warning-ignore:integer_division
 	var pivot = Vector2(_cel.get_width() / 2, _cel.get_height() / 2)
+
 	# Pivot correction in case of even size
-	if _cel.get_width() % 2 == 0:
-		pivot.x -= 0.5
-	if _cel.get_height() % 2 == 0:
-		pivot.y -= 0.5
+	if type_option_button.text != "Nearest neighbour (Shader)":
+		if _cel.get_width() % 2 == 0:
+			pivot.x -= 0.5
+		if _cel.get_height() % 2 == 0:
+			pivot.y -= 0.5
+
+	var selection_size := _cel.get_size()
+	var selection_tex := ImageTexture.new()
 
 	var image := Image.new()
 	image.copy_from(_cel)
@@ -45,36 +55,60 @@ func commit_action(_cel: Image, _project: Project = Global.current_project) -> v
 			selection_rectangle.position
 			+ ((selection_rectangle.end - selection_rectangle.position) / 2)
 		)
-		# Pivot correction in case of even size
-		if int(selection_rectangle.end.x - selection_rectangle.position.x) % 2 == 0:
-			pivot.x -= 0.5
-		if int(selection_rectangle.end.y - selection_rectangle.position.y) % 2 == 0:
-			pivot.y -= 0.5
-		image.lock()
-		_cel.lock()
-		for x in _project.size.x:
-			for y in _project.size.y:
-				var pos := Vector2(x, y)
-				if !_project.can_pixel_get_drawn(pos):
-					image.set_pixelv(pos, Color(0, 0, 0, 0))
-				else:
-					_cel.set_pixelv(pos, Color(0, 0, 0, 0))
-		image.unlock()
-		_cel.unlock()
+		selection_size = selection_rectangle.size
+
+		var selection: Image = _project.bitmap_to_image(_project.selection_bitmap)
+		selection_tex.create_from_image(selection, 0)
+
+		if type_option_button.text != "Nearest neighbour (Shader)":
+			# Pivot correction in case of even size
+			if int(selection_rectangle.end.x - selection_rectangle.position.x) % 2 == 0:
+				pivot.x -= 0.5
+			if int(selection_rectangle.end.y - selection_rectangle.position.y) % 2 == 0:
+				pivot.y -= 0.5
+			image.lock()
+			_cel.lock()
+			for x in _project.size.x:
+				for y in _project.size.y:
+					var pos := Vector2(x, y)
+					if !_project.can_pixel_get_drawn(pos):
+						image.set_pixelv(pos, Color(0, 0, 0, 0))
+					else:
+						_cel.set_pixelv(pos, Color(0, 0, 0, 0))
+			image.unlock()
+			_cel.unlock()
 	match type_option_button.text:
 		"Rotxel":
 			DrawingAlgos.rotxel(image, angle, pivot)
 		"Nearest neighbour":
 			DrawingAlgos.nn_rotate(image, angle, pivot)
 		"Upscale, Rotate and Downscale":
 			DrawingAlgos.fake_rotsprite(image, angle, pivot)
+		"Nearest neighbour (Shader)":
+			if !confirmed:
+				preview.material.set_shader_param("angle", angle)
+				preview.material.set_shader_param("selection_tex", selection_tex)
+				preview.material.set_shader_param("selection_pivot", pivot)
+				preview.material.set_shader_param("selection_size", selection_size)
+			else:
+				var params = {
+					"angle": angle,
+					"selection_tex": selection_tex,
+					"selection_pivot": pivot,
+					"selection_size": selection_size
+				}
+				var gen := ShaderImageEffect.new()
+				gen.generate_image(_cel, shader, params, _project.size)
+				yield(gen, "done")
+
 	if _project.has_selection and selection_checkbox.pressed:
 		_cel.blend_rect(image, Rect2(Vector2.ZERO, image.get_size()), Vector2.ZERO)
 	else:
 		_cel.blit_rect(image, Rect2(Vector2.ZERO, image.get_size()), Vector2.ZERO)
 
 
 func _confirmed() -> void:
+	confirmed = true
 	._confirmed()
 	angle_hslider.value = 0
 
@@ -92,6 +126,12 @@ func _on_SpinBox_value_changed(_value: float) -> void:
 
 
 func _on_TypeOptionButton_item_selected(_id: int) -> void:
+	if type_option_button.text == "Nearest neighbour (Shader)":
+		var sm = ShaderMaterial.new()
+		sm.shader = shader
+		preview.set_material(sm)
+	else:
+		preview.set_material(null)
 	update_preview()