Using a texture map to determine the colors of a toon outline?

Does anybody know the name of this technique and how I can apply it to the shader below? I remember doing this a long time ago with a shader script I found, but I can't find it.

 Shader "Toon/Basic Outline" {
     Properties {
         _Color ("Main Color", Color) = (.5,.5,.5,1)
         _OutlineColor ("Outline Color", Color) = (0,0,0,1)
         _Outline ("Outline width", Range (.002, 0.03)) = .005
         _MainTex ("Base (RGB)", 2D) = "white" { }
         _ToonShade ("ToonShader Cubemap(RGB)", CUBE) = "" { Texgen CubeNormal }
     }
     SubShader {
         Tags { "RenderType"="Opaque" }
         UsePass "Toon/Basic/BASE"
         Pass {
             Name "OUTLINE"
             Tags { "LightMode" = "Always" }
 CGPROGRAM
 #pragma vertex vert
 struct appdata {
     float4 vertex;
     float3 normal;
 };
 struct v2f {
     float4 pos : POSITION;
     float4 color : COLOR;
     float fog : FOGC;
 };
 uniform float _Outline;
 uniform float4 _OutlineColor;
 v2f vert(appdata v) {
     v2f o;
     o.pos = mul(glstate.matrix.mvp, v.vertex);
     float3 norm = mul ((float3x3)glstate.matrix.modelview[0], v.normal);
     norm.x *= glstate.matrix.projection[0][0];
     norm.y *= glstate.matrix.projection[1][1];
     o.pos.xy += norm.xy * _Outline;
  
     o.fog = o.pos.z;
     o.color = _OutlineColor;
     return o;
 }
 ENDCG
             //Color (0,0,0,0)
             Cull Front
             ZWrite On
             ColorMask RGB
             Blend SrcAlpha OneMinusSrcAlpha
             SetTexture [_MainTex] { combine primary }
         }
     }
  
     Fallback "Toon/Basic"
 }