Move get_ellipse_points() to DrawingAlgos

The same ellipse algorithm will be used for the circular brushes, as I can't seem to make the current circle algorithm work with even-numbered diameters.

src/Autoload/DrawingAlgos.gd

@@ -3,6 +3,73 @@ extends Node
 enum GradientDirection { TOP, BOTTOM, LEFT, RIGHT }
 
 
+# Algorithm based on http://members.chello.at/easyfilter/bresenham.html
+func get_ellipse_points(pos: Vector2, size: Vector2) -> Array:
+	var array := []
+	var x0 := int(pos.x)
+	var x1 := pos.x + int(size.x - 1)
+	var y0 := int(pos.y)
+	var y1 := int(pos.y) + int(size.y - 1)
+	var a := int(abs(x1 - x0))
+	var b := int(abs(y1 - x0))
+	var b1 := b & 1
+	var dx := 4 * (1 - a) * b * b
+	var dy := 4 * (b1 + 1) * a * a
+	var err := dx + dy + b1 * a * a
+	var e2 := 0
+
+	if x0 > x1:
+		x0 = x1
+		x1 += a
+
+	if y0 > y1:
+		y0 = y1
+
+# warning-ignore:integer_division
+	y0 += (b + 1) / 2
+	y1 = y0 - b1
+	a *= 8 * a
+	b1 = 8 * b * b
+
+	while x0 <= x1:
+		var v1 := Vector2(x1, y0)
+		var v2 := Vector2(x0, y0)
+		var v3 := Vector2(x0, y1)
+		var v4 := Vector2(x1, y1)
+		array.append(v1)
+		array.append(v2)
+		array.append(v3)
+		array.append(v4)
+
+		e2 = 2 * err
+
+		if e2 <= dy:
+			y0 += 1
+			y1 -= 1
+			dy += a
+			err += dy
+
+		if e2 >= dx || 2 * err > dy:
+			x0 += 1
+			x1 -= 1
+			dx += b1
+			err += dx
+
+	while y0 - y1 < b:
+		var v1 := Vector2(x0 - 1, y0)
+		var v2 := Vector2(x1 + 1, y0)
+		var v3 := Vector2(x0 - 1, y1)
+		var v4 := Vector2(x1 + 1, y1)
+		array.append(v1)
+		array.append(v2)
+		array.append(v3)
+		array.append(v4)
+		y0 += 1
+		y1 -= 1
+
+	return array
+
+
 func scale_3x(sprite: Image, tol: float = 50) -> Image:
 	var scaled := Image.new()
 	scaled.create(sprite.get_width() * 3, sprite.get_height() * 3, false, Image.FORMAT_RGBA8)

src/Tools/EllipseTool.gd

@@ -3,7 +3,7 @@ extends "res://src/Tools/ShapeDrawer.gd"
 
 func _get_shape_points_filled(size: Vector2) -> PoolVector2Array:
 	var offsetted_size := size + Vector2.ONE * (_thickness - 1)
-	var border := _get_ellipse_points(Vector2.ZERO, offsetted_size)
+	var border := DrawingAlgos.get_ellipse_points(Vector2.ZERO, offsetted_size)
 	var filling := []
 	var bitmap := _fill_bitmap_with_points(border, offsetted_size)
 
@@ -36,7 +36,7 @@ func _get_shape_points_filled(size: Vector2) -> PoolVector2Array:
 func _get_shape_points(size: Vector2) -> PoolVector2Array:
 	# Return ellipse with thickness 1
 	if _thickness == 1:
-		return PoolVector2Array(_get_ellipse_points(Vector2.ZERO, size))
+		return PoolVector2Array(DrawingAlgos.get_ellipse_points(Vector2.ZERO, size))
 
 	var size_offset := Vector2.ONE * (_thickness - 1)
 	var new_size := size + size_offset
@@ -50,8 +50,8 @@ func _get_shape_points(size: Vector2) -> PoolVector2Array:
 	# Adapted scanline algorithm to fill between 2 ellipses, to create a thicker ellipse
 	var res_array := []
 	var border_ellipses := (
-		_get_ellipse_points(Vector2.ZERO, new_size)
+		DrawingAlgos.get_ellipse_points(Vector2.ZERO, new_size)
-		+ _get_ellipse_points(size_offset, inner_ellipse_size)
+		+ DrawingAlgos.get_ellipse_points(size_offset, inner_ellipse_size)
 	)  # Outer and inner ellipses
 	var bitmap := _fill_bitmap_with_points(border_ellipses, new_size)
 	var smallest_side := min(new_size.x, new_size.y)
@@ -101,70 +101,3 @@ func _get_shape_points(size: Vector2) -> PoolVector2Array:
 				res_array.append(pos + mirror_smallest_side + mirror_largest_side)
 
 	return PoolVector2Array(res_array)
-
-
-# Algorithm based on http://members.chello.at/easyfilter/bresenham.html
-func _get_ellipse_points(pos: Vector2, size: Vector2) -> Array:
-	var array := []
-	var x0 := int(pos.x)
-	var x1 := pos.x + int(size.x - 1)
-	var y0 := int(pos.y)
-	var y1 := int(pos.y) + int(size.y - 1)
-	var a := int(abs(x1 - x0))
-	var b := int(abs(y1 - x0))
-	var b1 := b & 1
-	var dx := 4 * (1 - a) * b * b
-	var dy := 4 * (b1 + 1) * a * a
-	var err := dx + dy + b1 * a * a
-	var e2 := 0
-
-	if x0 > x1:
-		x0 = x1
-		x1 += a
-
-	if y0 > y1:
-		y0 = y1
-
-# warning-ignore:integer_division
-	y0 += (b + 1) / 2
-	y1 = y0 - b1
-	a *= 8 * a
-	b1 = 8 * b * b
-
-	while x0 <= x1:
-		var v1 := Vector2(x1, y0)
-		var v2 := Vector2(x0, y0)
-		var v3 := Vector2(x0, y1)
-		var v4 := Vector2(x1, y1)
-		array.append(v1)
-		array.append(v2)
-		array.append(v3)
-		array.append(v4)
-
-		e2 = 2 * err
-
-		if e2 <= dy:
-			y0 += 1
-			y1 -= 1
-			dy += a
-			err += dy
-
-		if e2 >= dx || 2 * err > dy:
-			x0 += 1
-			x1 -= 1
-			dx += b1
-			err += dx
-
-	while y0 - y1 < b:
-		var v1 := Vector2(x0 - 1, y0)
-		var v2 := Vector2(x1 + 1, y0)
-		var v3 := Vector2(x0 - 1, y1)
-		var v4 := Vector2(x1 + 1, y1)
-		array.append(v1)
-		array.append(v2)
-		array.append(v3)
-		array.append(v4)
-		y0 += 1
-		y1 -= 1
-
-	return array