Newbie GLSL to ShaderLab question

Hi I am a complete Unity newbie. I just downloaded it today. I wrote a simple game in Objective C for iOS and now I am trying to rewrite it using Unity basically just for fun and see if I can get it to run on my brother's Android phone.

Anyway I have a texture with some transparent parts and a model with certain vertex colours which I want to blend with the texture. The vertex colours have no alpha. So a place in the texture with 0 alpha would use just the vertex colour and if it was 1 it would use just the texture colour.

Here is the GLSL fragment shader:

Code (csharp):

1. uniform sampler2D u_texUnit;
2.  
3. varying mediump vec2 v_uv;
4. varying mediump vec3 v_color;
5.  
6. void main(void) {
7.     mediump vec4 texturePixel = texture2D(u_texUnit, v_uv);
8.     mediump vec3 color = (((v_color)*(1.0-texturePixel.a))+(texturePixel.rgb*texturePixel.a));
9.     gl_FragColor = vec4(color, 1.0);
10. }
11.  

Can anyone tell me the best way to rewrite this in Unity Shading?

Thanks.

 

Code (csharp):

1. Shader "Custom/NewShader" {
2.     Properties {
3.         _MainTex ("Base (RGB)", 2D) = "white" {}
4.     }
5.     SubShader {
6.         Tags { "RenderType"="Opaque" }
7.         LOD 200
8.        
9.         CGPROGRAM
10.         #pragma surface surf Lambert
11.  
12.         sampler2D _MainTex;
13.  
14.         struct Input {
15.             float2 uv_MainTex;
16.             float4 color : COLOR;
17.         };
18.  
19.         void surf (Input IN, inout SurfaceOutput o) {
20.             half4 c = tex2D (_MainTex, IN.uv_MainTex);
21.             o.Albedo = IN.color * (1.0-c.a) + c.rgb * c.a;
22.         }
23.         ENDCG
24.     }
25.     FallBack "Diffuse"
26. }
27.  

 

I don't understand why you were using mediump.