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How to make the effect of external glow using HLSL?

In WPF, OuterGlowBitmapEffect is no longer supported and Net4.0 is not displayed. DropShadow has a bit in common and is unacceptable in my case. My initial goal is to make the white blurry background with black ClearType text in the AeroGlass window to make it more readable in dark scenes. I started playing with fx and HLSL. It's quite interesting and powerful, but I still can't get close to OuterGlowBitmapEffect.

My current dummy version that reflects the idea:

sampler2D  Sampler : register(S0);
#define PI 3.14f
float4 main(float2 uv : TEXCOORD) : COLOR
{
    float4 px = tex2D(Sampler, uv);

    /*
    if (px.a > 0.9)
    {
        return px;
    }
    */

    const float d = 3;

    int cnt = 0;
    float a = 0;
    for (float x = -0.1*d; x < 0.1*d; x += 0.05*d)
    {
        a += tex2D(Sampler, uv + float2(x, 0)).a;
        a += tex2D(Sampler, uv + float2(0, x)).a;
        a += tex2D(Sampler, uv + x).a;
        cnt += 3;
    }
    a /= cnt;

    float4 s = a;

    float4 r = float4(px.rgb*px.a + s.rgb*(1-px.a), max(px.a, a));

    return r;
}

BTW: can I get the HLSL source for DropShadowEffect to use as a reference? Can someone point me to the OuterGlowEffect algorithm in any language?

. Windows 7 Aero Glass , ! , ( DwmExtendFrameIntoClientArea) Aero Glass Window Title

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1

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- , (, x = 0). : . HLSL:

float4 PS_BlurHorizontal( float2 Tex : TEXCOORD0 ) : COLOR0
{
    float Color = 0.0f;

    Color += tex2D(sampler, float2(Tex.x - 3.0*blurSizeX, Tex.y)) * 0.09f;
    Color += tex2D(sampler, float2(Tex.x - 2.0*blurSizeX, Tex.y)) * 0.11f;
    Color += tex2D(sampler, float2(Tex.x - blurSizeX, Tex.y)) * 0.18f;
    Color += tex2D(sampler, Tex) * 0.24f;
    Color += tex2D(sampler, float2(Tex.x + blurSizeX, Tex.y)) * 0.18f;
    Color += tex2D(sampler, float2(Tex.x + 2.0*blurSizeX, Tex.y)) * 0.11f;
    Color += tex2D(sampler, float2(Tex.x + 3.0*blurSizeX, Tex.y)) * 0.09f;

    return Color;
}

float4 PS_BlurVertical( float2 Tex : TEXCOORD0 ) : COLOR0
{
    float Color = 0.0f;

    Color += tex2D(sampler, float2(Tex.x, Tex.y - 3.0*blurSizeY)) * 0.09f;
    Color += tex2D(sampler, float2(Tex.x, Tex.y - 2.0*blurSizeY)) * 0.11f;
    Color += tex2D(sampler, float2(Tex.x, Tex.y - blurSizeY)) * 0.18f;
    Color += tex2D(sampler, Tex) * 0.24f;
    Color += tex2D(sampler, float2(Tex.x, Tex.y + blurSizeY)) * 0.18f;
    Color += tex2D(sampler, float2(Tex.x, Tex.y + 2.0*blurSizeY)) * 0.11f;
    Color += tex2D(sampler, float2(Tex.x, Tex.y + 3.0*blurSizeY)) * 0.09f;

    return Color;
}
// weights: 0.09 + 0.11 + 0.18 + 0.24 + 0.18 + 0.11 + 0.9 = 1
// By default, weigths are symmetrical and sum up to 1,
// but they don't necessarily have to.
// You can change the weights to create more fancy results.

These two 7-sample passes simulate 7x7 Gaussian blur (14 samples instead of 49). You can use more samples to improve the result (make the blur wider) or simply adjust the scales to create a softer look.

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