diff --git a/src/Autoload/DrawingAlgos.gd b/src/Autoload/DrawingAlgos.gd
index 6a668fea8..3b77da36b 100644
--- a/src/Autoload/DrawingAlgos.gd
+++ b/src/Autoload/DrawingAlgos.gd
@@ -127,7 +127,7 @@ func get_ellipse_points(pos: Vector2i, size: Vector2i) -> Array[Vector2i]:
 	var y0 := pos.y
 	var y1 := pos.y + (size.y - 1)
 	var a := absi(x1 - x0)
-	var b := absi(y1 - x0)
+	var b := absi(y1 - y0)
 	var b1 := b & 1
 	var dx := 4 * (1 - a) * b * b
 	var dy := 4 * (b1 + 1) * a * a
diff --git a/src/Classes/SelectionMap.gd b/src/Classes/SelectionMap.gd
index abdc3329c..d5a89186a 100644
--- a/src/Classes/SelectionMap.gd
+++ b/src/Classes/SelectionMap.gd
@@ -175,7 +175,65 @@ func resize_bitmap_values(
 	else:
 		project.selection_offset.y = 0
 	clear()
-	smaller_image.resize(new_size.x, new_size.y, Image.INTERPOLATE_NEAREST)
+
+	var is_ellipse_select := true
+	var w := smaller_image.get_width()
+	var h := smaller_image.get_height()
+	var ellipse_select := DrawingAlgos.get_ellipse_points(Vector2.ZERO, Vector2i(w, h))
+	var x_min := []
+	var x_max := []
+	x_min.resize(h)
+	x_max.resize(h)
+	# Determine x_min and x_max of y
+	for i in ellipse_select.size() / 2:
+		i *= 2
+		var y := ellipse_select[i].y
+		var xmin := (
+			ellipse_select[i].x
+			if ellipse_select[i].x < ellipse_select[i + 1].x
+			else ellipse_select[i + 1].x
+		)
+		var xmax := (
+			ellipse_select[i].x
+			if ellipse_select[i].x >= ellipse_select[i + 1].x
+			else ellipse_select[i + 1].x
+		)
+
+		if x_min[y] == null && x_max[y] == null:
+			x_min[y] = xmin
+			x_max[y] = xmax
+		else:
+			if x_min[y] != null && x_min[y] > xmin:
+				x_min[y] = xmin
+			if x_max[y] != null && x_max[y] < xmax:
+				x_max[y] = xmax
+	# too small to be rectangular selection
+	if x_min[0] == 0 && x_max[0] == w - 1:
+		is_ellipse_select = false
+	# if ellipse is too small, ellipse_select doesn't quite cover the true elliptical selection
+	for y in range(h):
+		if x_min[y] == null:
+			is_ellipse_select = false
+	# Determine whether the selection is an ellipse selection
+	for y in range(h):
+		if !is_ellipse_select:
+			break
+		for x in range(w):
+			if smaller_image.get_pixel(x, y) == Color(1, 1, 1, 1) && (x < x_min[y] || x > x_max[y]):
+				is_ellipse_select = false
+				break
+	# if selection is an ellipse selection, resized as standard ellipse
+	if !is_ellipse_select:
+		smaller_image.resize(new_size.x, new_size.y, Image.INTERPOLATE_BILINEAR)
+	else:
+		var resized_img := Image.create(new_size.x, new_size.y, false, smaller_image.get_format())
+		var new_ellipse_select := DrawingAlgos.get_ellipse_points_filled(
+			Vector2.ZERO, Vector2i(new_size.x, new_size.y)
+		)
+		for p in new_ellipse_select:
+			resized_img.set_pixel(p.x, p.y, Color(1, 1, 1, 1))
+		smaller_image = resized_img
+
 	if flip_hor:
 		smaller_image.flip_x()
 	if flip_ver: