Mask and blurred image

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1

Hi, I am trying to replicate a flashlight effect for my top view game.
I got this code working ok

local pd <const> = playdate
local gfx <const> = playdate.graphics

class('Night').extends(gfx.sprite)

function Night:init(player) 

    self.player = player
    self.shadeImage = gfx.image.new(400, 240, gfx.kColorBlack)
    self.shadeImage:addMask()

    self:setImage(self.shadeImage)
    self:setSize(400, 240)
    self:setCenter(0,0)
    self:moveTo(0, 0)
    self:setZIndex(100)
    self:add()

end

function Night:update() 

    local shadeMask = self.shadeImage:getMaskImage()
    self.shadeImage:clearMask(1)
    gfx.pushContext( shadeMask )
    gfx.fillCircleAtPoint( self.player.posx, self.player.posy, 50)
    gfx.popContext()

end

this code creates a black image except for the player position in a radius of 50. But I want that the black image is not black, I want a blurred or faded image, but nothing works for me, I tested with:

gfx.image.new(400, 240, gfx.kColorBlack):blurredImage(0,0 ,50, 2, playdate.graphics.image.kDitherTypeBayer8x8)

with

self.shadeImage = self.shadeImage:blurredImage(0,0 ,50, 2, playdate.graphics.image.kDitherTypeBayer8x8)

but nothing works. What am I doing wrong?
Thanks so much