local sprite = app.activeSprite
local from_layer = sprite.layers[1]
local frame_num = 1
local from_cel = from_layer:cel(frame_num)

app.useTool {
    tool = "magic_wand",
    layer = from_layer,
    cel = from_cel,
    button = MouseButton.LEFT,
    points = {from_cel.position},
    selection = SelectionMode.REPLACE
}
app.command.Cut()
local to_layer = sprite:newLayer()
app.activeLayer = to_layer
app.activeFrame = to_layer.sprite.frames[1]
app.activeLayer = to_layer
app.command.Paste()

local without_ext = app.fs.filePathAndTitle(app.activeSprite.filename)
app.command.SaveFile {
    ["filename"] = without_ext .. ".ase",
    ["filename-format"] = ".ase",
}