右边两个是换色实现的

原图

遮罩图

image.png

用红、绿、蓝、黑分别在遮罩图上标识不同的部分，以便在Shader里进行着色处理:

Shader "Custom/ColorAdjustmentWithMaskHSVOptimized"
{
    Properties
    {
        _MainTex ("Main Texture", 2D) = "white" {}
        _MaskTex ("Mask Texture", 2D) = "white" {}

        _HueR ("Red Hue", Range(-0.5, 0.5)) = 0
        _SaturationR ("Red Saturation", Range(0, 2)) = 1
        _ValueR ("Red Value", Range(0, 2)) = 1

        _HueG ("Green Hue", Range(-0.5, 0.5)) = 0
        _SaturationG ("Green Saturation", Range(0, 2)) = 1
        _ValueG ("Green Value", Range(0, 2)) = 1

        _HueB ("Blue Hue", Range(-0.5, 0.5)) = 0
        _SaturationB ("Blue Saturation", Range(0, 2)) = 1
        _ValueB ("Blue Value", Range(0, 2)) = 1
    }
    SubShader
    {
        Tags
        {
            "RenderType"="Opaque"
        }
        LOD 200
        Blend SrcAlpha OneMinusSrcAlpha

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

            sampler2D _MainTex;
            sampler2D _MaskTex;

            float _HueR, _SaturationR, _ValueR;
            float _HueG, _SaturationG, _ValueG;
            float _HueB, _SaturationB, _ValueB;

            float3 rgb2hsv(float3 c)
            {
                // RGB 转 HSV
                float4 K = float4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0);
                float4 p = lerp(float4(c.bg, K.wz), float4(c.gb, K.xy), step(c.b, c.g));
                float4 q = lerp(float4(p.xyw, c.r), float4(c.r, p.yzx), step(p.x, c.r));

                float d = q.x - min(q.w, q.y);
                float e = 1.0e-10;
                return float3(abs(q.z + (q.w - q.y) / (6.0 * d + e)), d / (q.x + e), q.x);
            }

            float3 hsv2rgb(float3 c)
            {
                // HSV 转 RGB
                c = float3(c.x, clamp(c.yz, 0.0, 1.0));
                float4 K = float4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
                float3 p = abs(frac(c.xxx + K.xyz) * 6.0 - K.www);
                return c.z * lerp(K.xxx, clamp(p - K.xxx, 0.0, 1.0), c.y);
            }

            fixed4 adjustColor(fixed4 color, float H, float S, float V)
            {
                float3 hsv = rgb2hsv(color.rgb);
                hsv.x += H;
                hsv.y *= S;
                hsv.z *= V;
                return fixed4(hsv2rgb(hsv), color.a);
            }

            fixed3 adjustColorSimple(fixed3 hsv, float H, float S, float V)
            {
                hsv.x += H;
                hsv.y *= S;
                hsv.z *= V;
                return hsv2rgb(hsv);
            }

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

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

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

            fixed4 frag(v2f i) : SV_Target
            {
                fixed4 mainColor = tex2D(_MainTex, i.uv);
                fixed4 maskColor = tex2D(_MaskTex, i.uv);

                // 使用直接比较判断掩码颜色是否为黑色
                float isBlackMask = step(1.0, maskColor.r + maskColor.g + maskColor.b);

                // 调整颜色并组合
                float3 hsvColor = rgb2hsv(mainColor.rgb);
                fixed3 finalColor =
                    adjustColorSimple(hsvColor, _HueR, _SaturationR, _ValueR) * maskColor.r +
                    adjustColorSimple(hsvColor, _HueG, _SaturationG, _ValueG) * maskColor.g +
                    adjustColorSimple(hsvColor, _HueB, _SaturationB, _ValueB) * maskColor.b;

                // 确保颜色在 [0, 1] 范围内
                finalColor.rgb = clamp(finalColor.rgb, 0.0, 1.0);

                // 如果是黑色掩码，返回原色
                return lerp(mainColor, float4(finalColor, mainColor.a), isBlackMask);
            }
            ENDCG
        }
    }
    FallBack "Diffuse"
}

本来想用PhotoShop的HSL调色方案的，折腾半天没搞定，就用HSV了。
其实A通道也可以用上，不过目前3个已经够了，先保留吧。
这个也可以用在Spine上，保持相同的图集布局即可，没了。