Well the first thing you would do is define a .FX file. In that you need code like the following:
uniform extern texture Image1;
uniform extern texture Image2;
sampler2D BG_Image1_Sampler = sampler_state
{
Texture = (Image1);
MinFilter = LINEAR;
MagFilter = LINEAR;
MipFilter = LINEAR;
};
sampler2D BG_Image2_Sampler = sampler_state
{
Texture = (Image2);
MinFilter = LINEAR;
MagFilter = LINEAR;
MipFilter = LINEAR;
};
float4 MyCalcFunction(float2 TexCoords : TEXCOORD0) : COLOR0
{
float4 outColor;
//calculations here
return outColor;
}
technique BlurGlow
{
pass P0
{
PixelShader = compile ps_2_0 MyCalcFunction();
}
}
I'm unsure of how to use the FX file with silverlight but that should get you started!