unity 图片置灰shader

我和chatgpt真强！

在 Unity 编辑器中，右键点击 Assets 文件夹，选择 Create -> Shader -> Unlit Shader。shader代码如下，尽管我看的不是很懂，但确实有用

Shader "Custom/GrayScaleShader"
{
    Properties
    {
        _MainTex ("Base (RGB)", 2D) = "white" {}
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            struct appdata_t
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float4 pos : POSITION;
                float2 uv : TEXCOORD0;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;

            v2f vert (appdata_t v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                return o;
            }

            half4 frag (v2f i) : SV_Target
            {
                half4 color = tex2D(_MainTex, i.uv);
                float gray = dot(color.rgb, half3(0.299, 0.587, 0.114));
                return half4(gray, gray, gray, color.a);
            }
            ENDCG
        }
    }
}

再创建一个材质并应用 Shader：
右键点击 Assets 文件夹，选择 Create -> Material，创建一个新材质，在材质的 Shader 下拉列表中选择你刚刚创建的shader

应用材质

在将这个材质应用于我们的图片

效果展示

感觉还不错

2024-10-02更新

我发现个问题，上述的sharder会把其他通道也算上，导致置灰效果很奇怪，又找了一版sharder

Shader "UI/ImageGreyShader"
{
    Properties
    {
        [PerRendererData] _MainTex("Sprite Texture", 2D) = "white" {}
        _Color("Tint", Color) = (1,1,1,1)
    }

        SubShader
    {
        Tags
    {
        "Queue" = "Transparent"
        "IgnoreProjector" = "True"
        "RenderType" = "Transparent"
        "PreviewType" = "Plane"
        "CanUseSpriteAtlas" = "True"
    }
        // 源rgba*源a + 背景rgba*(1-源A值)   
        Blend SrcAlpha OneMinusSrcAlpha

        Pass
    {
        CGPROGRAM
#pragma vertex vert     
#pragma fragment frag     
#include "UnityCG.cginc"     

        struct appdata_t
    {
        float4 vertex   : POSITION;
        float4 color    : COLOR;
        float2 texcoord : TEXCOORD0;
    };

    struct v2f
    {
        float4 vertex   : SV_POSITION;
        fixed4 color : COLOR;
        half2 texcoord  : TEXCOORD0;
    };

    sampler2D _MainTex;
    fixed4 _Color;

    v2f vert(appdata_t IN)
    {
        v2f OUT;
        OUT.vertex = mul(UNITY_MATRIX_MVP, IN.vertex);
        OUT.texcoord = IN.texcoord;
#ifdef UNITY_HALF_TEXEL_OFFSET     
        OUT.vertex.xy -= (_ScreenParams.zw - 1.0);
#endif     
        OUT.color = IN.color * _Color;
        return OUT;
    }

    fixed4 frag(v2f IN) : SV_Target
    {
        half4 color = tex2D(_MainTex, IN.texcoord) * IN.color;
        float grey = dot(color.rgb, fixed3(0.22, 0.707, 0.071));
        return half4(grey,grey,grey,color.a);
    }
        ENDCG
    }
    }
}