偶然在国外网站上看到的一个脚本，通过纯色背景抠像的方法，把windows的窗体透明化，可以用来做无背景的小头像、桌面精灵等。

首先新建一个叫TransparentWindow的CS脚本，输入如下代码：

using System;
using System.Runtime.InteropServices;
using UnityEngine;public class TransparentWindow : MonoBehaviour
{[SerializeField]private Material m_Material;private struct MARGINS{public int cxLeftWidth;public int cxRightWidth;public int cyTopHeight;public int cyBottomHeight;}// Define function signatures to import from Windows APIs[DllImport("user32.dll")]private static extern IntPtr GetActiveWindow();[DllImport("user32.dll")]private static extern int SetWindowLong(IntPtr hWnd, int nIndex, uint dwNewLong);[DllImport("Dwmapi.dll")]private static extern uint DwmExtendFrameIntoClientArea(IntPtr hWnd, ref MARGINS margins);// Definitions of window stylesconst int GWL_STYLE = -16;const uint WS_POPUP = 0x80000000;const uint WS_VISIBLE = 0x10000000;void Start(){
#if !UNITY_EDITORvar margins = new MARGINS() { cxLeftWidth = -1 };// Get a handle to the windowvar hwnd = GetActiveWindow();// Set properties of the window// See: https://msdn.microsoft.com/en-us/library/windows/desktop/ms633591%28v=vs.85%29.aspxSetWindowLong(hwnd, GWL_STYLE, WS_POPUP | WS_VISIBLE);// Extend the window into the client area//See: https://msdn.microsoft.com/en-us/library/windows/desktop/aa969512%28v=vs.85%29.aspx DwmExtendFrameIntoClientArea(hwnd, ref margins);
#endif}// Pass the output of the camera to the custom material// for chroma replacementvoid OnRenderImage(RenderTexture from, RenderTexture to){Graphics.Blit(from, to, m_Material);}
}

然后新建一个叫ChromakeyTransparent的Shader：

Shader "Custom/ChromakeyTransparent" {Properties{_MainTex("Base (RGB)", 2D) = "white" {}_TransparentColourKey("Transparent Colour Key", Color) = (0,0,0,1)_TransparencyTolerance("Transparency Tolerance", Float) = 0.01}SubShader{Pass{Tags{ "RenderType" = "Opaque" }LOD 200CGPROGRAM#pragma vertex vert#pragma fragment frag#include "UnityCG.cginc"struct a2v{float4 pos : POSITION;float2 uv : TEXCOORD0;};struct v2f{float4 pos : SV_POSITION;float2 uv : TEXCOORD0;};v2f vert(a2v input){v2f output;output.pos = UnityObjectToClipPos(input.pos);output.uv = input.uv;return output;}sampler2D _MainTex;float3 _TransparentColourKey;float _TransparencyTolerance;float4 frag(v2f input) : SV_Target{// What is the colour that *would* be rendered here?float4 colour = tex2D(_MainTex, input.uv);// Calculate the different in each component from the chosen transparency colourfloat deltaR = abs(colour.r - _TransparentColourKey.r);float deltaG = abs(colour.g - _TransparentColourKey.g);float deltaB = abs(colour.b - _TransparentColourKey.b);// If colour is within tolerance, write a transparent pixelif (deltaR < _TransparencyTolerance && deltaG < _TransparencyTolerance && deltaB < _TransparencyTolerance){return float4(0.0f, 0.0f, 0.0f, 0.0f);}// Otherwise, return the regular colourreturn colour;}ENDCG}}
}

新建一个材质，选择我们刚刚写好的Shader，将TransparentWindow挂载到摄像机上，摄像机的Clear Flags选择Solid Color，Background选择和材质的Transparent Color Key相同的颜色（建议选择与模型边缘颜色相近的颜色，不然会出现较明显的毛边），将材质拖拽给TransparentWindow的Material变量。

运行之后可以看到背景颜色已经被扣掉（黑色其实是透明）：

Build一下之后我们就可以看到类似桌面精灵的一个程序了：