FNA shader effect example

EffectContainer.cs

    using Microsoft.Xna.Framework.Graphics;
    using MyGame.IO;

    namespace MyGame.Containers
    {
        public sealed class EffectContainer
        {
            public Effect SoftLightEffect { get; }

            public EffectContainer(GraphicsDevice graphicsDevice)
            {
                SoftLightEffect = EffectLoader.LoadEffect(graphicsDevice, "Effects/SoftLightEffect.fxb");
            }

            public void Unload()
            {
                SoftLightEffect.Dispose();
            }
        }
    }

EffectLoader.cs

    using Microsoft.Xna.Framework.Graphics;

    namespace MyGame.IO
    {
        public static class EffectLoader
        {
            public static Effect LoadEffect(GraphicsDevice graphicsDevice, string path)
            {
                return new Effect(graphicsDevice, ContentIO.ReadAllBytes(path));
            }
        }
    }

SoftLightEffect.fx

// Soft light blend mode using Pegtop's formula.

sampler SourceTexture : register(s0);
sampler BlendTexture : register(s1);

float blendAlpha;

float3 Blend(float3 base, float3 blend)
{
    return (1.0 - 2.0 * blend) * base * base + 2.0 * base * blend;
}

float3 Blend(float3 base, float3 blend, float opacity)
{
    return (Blend(base, blend) * opacity + base * (1.0 - opacity));
}

float4 PixelShaderFunction(float4 color : COLOR0, float2 texCoord : TEXCOORD0) : COLOR0
{
    float4 sourceColor = tex2D(SourceTexture, texCoord);
    float4 blendColor = tex2D(BlendTexture, texCoord);

	return float4(Blend(sourceColor.rgb, blendColor.rgb, blendAlpha), 1.0);
}

technique Technique1
{
    pass Pass1
    {
        PixelShader = compile ps_3_0 PixelShaderFunction();
    }
}