Color ramp shader

<?xml version="1.0" encoding="UTF-8"?>
<!--
    RAMP SHADER
    -->
<shader language="HLSL">
  <source><![CDATA[
  //These variables will get set automatically
texture rubyTexture;

sampler s0 = sampler_state { texture = <rubyTexture>; };

float ramp(float c)
{
    return c > 0.5 ? c : 0.24*c + 2.22*c*c - 1.4*c*c*c;
}

float4 NormalColourPass( in float2 Tex : TEXCOORD0 ) : COLOR0
{
    float4 color = tex2D( s0, Tex );
    color.a = 1;

    color.r = ramp(color.r);
    color.g = ramp(color.g);
    color.b = ramp(color.b);

    return color;
}

Technique T0
{
    pass p0 { PixelShader = compile ps_2_0 NormalColourPass(); }
}
  ]]></source>
</shader>