考虑到法向贴图（normal mapping）和程序贴图纹理（procedural textures）两节的内容要么很常见或者很少使用，因此我决定偷懒先不看了。
终于到了Using Textures for Effects的最后一节！这次主要讲一个小技巧，用Shader实现Photoshop的色阶效果。
如果你曾经做过图像编辑工作，例如给你们家的一张合影调色啊，制作游戏贴等，那么你一定明白使用色阶来全局调整图像的重要性和实用性。现在，可以告诉你，你完全可以使用Shaders来创建类似Photoshop色阶的效果。
Photoshop里所有的图像编辑工具和混合模型就是一系列数学操作的结果。从本质上来说，我们是在对像素值与其他某些量进行乘法、加法、除法、或者比较等操作，来得到最后的返回值。这个返回值就是新图像的一个像素值。
当然，我们可以写一大本书来仅仅描述Photoshop效果使用的数学技巧，但这里，我们仅仅关注色阶这一块。在本书的第十章，Screen Effects with Unity Render Textures中，将会涉及更多的高级混合模式。（噢，第十章感觉好远的样子。）
Properties {
_MainTex ("Base (RGB)", 2D) = "white" {}
//Add the Input Levels Values
_inBlack ("Input Black", Range(0, 255)) = 0
_inGamma ("Input Gamma", Range(0, 2)) = 1.61
_inWhite ("Input White", Range(0, 255)) = 255
//Add the Output Levels
_outWhite ("Output White", Range(0, 255)) = 255
_outBlack ("Output Black", Range(0, 255)) = 0
}CGPROGRAM #pragma surface surf Lambert sampler2D _MainTex; //Add these variables //to the CGPROGRAM float _inBlack; float _inGamma; float _inWhite; float _outWhite; float _outBlack;
float GetPixelLevel(float pixelColor)
{
float pixelResult;
pixelResult = (pixelColor * 255.0);
pixelResult = max(0, pixelResult - _inBlack);
pixelResult = saturate(pow(pixelResult / (_inWhite - _inBlack), _inGamma));
pixelResult = (pixelResult * (_outWhite - _outBlack) + _outBlack)/255.0;
return pixelResult;
}//Create a variable to store //a pixel channel from our _MainTex texture float outRPixel = GetPixelLevel(c.r); float outGPixel = GetPixelLevel(c.g); float outBPixel = GetPixelLevel(c.b);
o.Albedo = float3(outRPixel,outGPixel,outBPixel); o.Alpha = c.a;
Shader "Custom/PhotoshopLevels" {
Properties {
_MainTex ("Base (RGB)", 2D) = "white" {}
//Add the Input Levels Values
_inBlack ("Input Black", Range(0, 255)) = 0
_inGamma ("Input Gamma", Range(0, 2)) = 1.61
_inWhite ("Input White", Range(0, 255)) = 255
//Add the Output Levels
_outWhite ("Output White", Range(0, 255)) = 255
_outBlack ("Output Black", Range(0, 255)) = 0
}
SubShader {
Tags { "RenderType"="Opaque" }
LOD 200
CGPROGRAM
#pragma surface surf Lambert
sampler2D _MainTex;
//Add these variables
//to the CGPROGRAM
float _inBlack;
float _inGamma;
float _inWhite;
float _outWhite;
float _outBlack;
struct Input {
float2 uv_MainTex;
};
float GetPixelLevel(float pixelColor)
{
float pixelResult;
pixelResult = (pixelColor * 255.0);
pixelResult = max(0, pixelResult - _inBlack);
pixelResult = saturate(pow(pixelResult / (_inWhite - _inBlack), _inGamma));
pixelResult = (pixelResult * (_outWhite - _outBlack) + _outBlack)/255.0;
return pixelResult;
}
void surf (Input IN, inout SurfaceOutput o) {
half4 c = tex2D (_MainTex, IN.uv_MainTex);
//Create a variable to store
//a pixel channel from our _MainTex texture
float outRPixel = GetPixelLevel(c.r);
float outGPixel = GetPixelLevel(c.g);
float outBPixel = GetPixelLevel(c.b);
o.Albedo = float3(outRPixel,outGPixel,outBPixel);
o.Alpha = c.a;
}
ENDCG
}
FallBack "Diffuse"
}
pixelResult = (pixelColor * 255.0);
pixelResult = max(0, pixelResult - _inBlack);
pixelResult = saturate(pow(pixelResult / (_inWhite - _inBlack), _inGamma));
pixelResult = (pixelResult * (_outWhite - _outBlack) + _outBlack)/255.0;
【Unity Shaders】Using Textures for Effects —— 实现Photoshop的色阶效果,布布扣,bubuko.com
【Unity Shaders】Using Textures for Effects —— 实现Photoshop的色阶效果
原文：http://blog.csdn.net/candycat1992/article/details/21228945