Pixel prefect outline shader in Solar2D

pixeloutline.lua

--local object = display.newImage("image.png")

--object.fill.effect = "filter.custom.pixeloutline"
--object.fill.effect.intensity   = 0.0 to 10.0 -- how thick is it
--object.fill.effect.r, g, b   = 4 to 50 -- color

local kernel = {}

kernel.language = "glsl"
kernel.category = "filter"
kernel.name = "pixeloutline"

kernel.vertexData   = {
  {
    name    = "r",
    default = 0,
    min     = 0,
    max     = 1,
    index   = 0,
    },{
    name    = "g",
    default = 0,
    min     = 0,
    max     = 1,
    index   = 1,
    },{
    name    = "b",
    default = 0,
    min     = 0,
    max     = 1,
    index   = 2,
    },{
    name    = "size",
    default = 1,
    min     = 0,
    max     = 4,
    index   = 3,
  },
}
kernel.fragment = [[

P_NORMAL float size = CoronaVertexUserData.w;
P_COLOR vec4 FragmentKernel( P_UV vec2 texCoord )
{
  P_COLOR vec4 texColor = texture2D( CoronaSampler0, texCoord );
    if (texColor.a == 0.0)
    {
    P_NORMAL float w = size * CoronaTexelSize.x;
    P_NORMAL float h = size * CoronaTexelSize.y;
        if (texture2D(CoronaSampler0, texCoord + vec2(w, 0.0)).a != 0.0 ||
            texture2D(CoronaSampler0, texCoord + vec2(-w, 0.0)).a != 0.0 ||
            texture2D(CoronaSampler0, texCoord + vec2(0.0, h)).a != 0.0 ||
            texture2D(CoronaSampler0, texCoord + vec2(0.0,-h)).a != 0.0)
            texColor.rgba = vec4(CoronaVertexUserData.x,CoronaVertexUserData.y,CoronaVertexUserData.z,1);
    }
    return CoronaColorScale(texColor);
}
]]

graphics.defineEffect( kernel )

So you will need to leave a 1px border around the image for the outline to work. In this example there's no border on the bottom, so his feet aren't outlined.