Untiy Shader——颜色拾取器

Shader "Simple Shader" {
    Properties {
        _Color ("Color Tint", Color) = (1, 1, 1, 1)
    }
    SubShader {
        Pass {
            CGPROGRAM

            #include "UnityCG.cginc"

            #pragma vertex vert
            #pragma fragment frag
            
            uniform fixed4 _Color;

            struct a2v {
                //POSITION语义告诉Unity：用模型空间的顶点坐标填充到vertex变量
                float4 vertex : POSITION;
                //NORMAL语义告诉Unity：用模型空间的法线方向填充normal方向
                float3 normal : NORMAL;
                //TEXCOORD0语义告诉Unity：用模型的第一套纹理坐标填充textcoord变量
                float4 texcoord : TEXCOORD0;
            };
            
            struct v2f {
                //SV_POSITION语义告诉Unity：pos里包含了顶点在裁剪空间中的位置信息
                float4 pos : SV_POSITION;
                fixed3 color : COLOR0;
            };
            
            v2f vert(a2v v) {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                o.color = v.normal * 0.5 + fixed3(0.5, 0.5, 0.5);
                return o;
            }

            fixed4 frag(v2f i) : SV_Target {
                fixed3 c = i.color;
                c *= _Color.rgb;
                return fixed4(c, 1.0);
            }

            ENDCG
        }
    }
}

using UnityEngine;
using System.Collections;

public class ColorPicker : MonoBehaviour {
    
    public BoxCollider pickerCollider;

    private bool m_grab;
    private Camera m_camera;
    private Texture2D m_screenRenderTexture;
    private static Texture2D m_staticRectTexture;
    private static GUIStyle m_staticRectStyle;

    private static Vector3 m_pixelPosition = Vector3.zero;
    private Color m_pickedColor = Color.white;

    void Awake() {
        // Get the Camera component
        m_camera = GetComponent<Camera>();
        if (m_camera == null) {
            Debug.LogError("You need to dray this script to a camera!");
            return;
        }

        // Attach a BoxCollider to this camera
        // In order to receive mouse events
        if (pickerCollider == null) {
            pickerCollider = gameObject.AddComponent<BoxCollider>();
            // Make sure the collider is in the camera's frustum
            pickerCollider.center = Vector3.zero;
            pickerCollider.center += m_camera.transform.worldToLocalMatrix.MultiplyVector(m_camera.transform.forward) * (m_camera.nearClipPlane + 0.2f);
            pickerCollider.size = new Vector3(Screen.width, Screen.height, 0.1f);
        }
    }

    // Draw the color we picked
    public static void GUIDrawRect( Rect position, Color color )
    {
        if( m_staticRectTexture == null )
        {
            m_staticRectTexture = new Texture2D(1, 1);
        }
        
        if( m_staticRectStyle == null )
        {
            m_staticRectStyle = new GUIStyle();
        }
        
        m_staticRectTexture.SetPixel(0, 0, color);
        m_staticRectTexture.Apply();
        
        m_staticRectStyle.normal.background = m_staticRectTexture;
        
        GUI.Box(position, GUIContent.none, m_staticRectStyle);
    }

    // OnPostRender is called after a camera has finished rendering the scene.
    // This message is sent to all scripts attached to the camera.
    // Use it to grab the screen
    // Note: grabing is a expensive operation
    void OnPostRender() {
        if (m_grab) {
            m_screenRenderTexture = new Texture2D(Screen.width, Screen.height);
            m_screenRenderTexture.ReadPixels(new Rect(0, 0, Screen.width, Screen.height), 0, 0);
            m_screenRenderTexture.Apply();
            m_pickedColor = m_screenRenderTexture.GetPixel(Mathf.FloorToInt(m_pixelPosition.x), Mathf.FloorToInt(m_pixelPosition.y));
            m_grab = false;
        }
    }
    
    void OnMouseDown() {
        m_grab = true;
        // Record the mouse position to pick pixel
        m_pixelPosition = Input.mousePosition;
    }

    void OnGUI() {
        GUI.Box(new Rect(0, 0, 120, 200), "Color Picker");
        GUIDrawRect(new Rect(20, 30, 80, 80), m_pickedColor);
        GUI.Label(new Rect(10, 120, 100, 20), "R: " + System.Math.Round((double)m_pickedColor.r, 4) + "\t(" + Mathf.FloorToInt(m_pickedColor.r * 255)+ ")");
        GUI.Label(new Rect(10, 140, 100, 20), "G: " + System.Math.Round((double)m_pickedColor.g, 4) + "\t(" + Mathf.FloorToInt(m_pickedColor.g * 255)+ ")");
        GUI.Label(new Rect(10, 160, 100, 20), "B: " + System.Math.Round((double)m_pickedColor.b, 4) + "\t(" + Mathf.FloorToInt(m_pickedColor.b * 255)+ ")");
        GUI.Label(new Rect(10, 180, 100, 20), "A: " + System.Math.Round((double)m_pickedColor.a, 4) + "\t(" + Mathf.FloorToInt(m_pickedColor.a * 255)+ ")");
    }
}