如何在Asp.net中使用HSL

Question

什麼工具用於處理.net中的HSL顏色？

Answer 1

顏色結構提供了三種方法：GetHue，GetSaturation和GetBrightness。

鮑勃鮑威爾幾年前寫了interesting piece on this。

奇怪的歷史說明 - 「HSL」（以及相關的「HSV」）是在70年代，禮貌的Alvy Ray Smith從施樂公司的帕洛阿爾託研究中心（PARC）發起的許多事情之一。

Answer 2

這個ColorRGB類提供了獲取和設置HSL的方法，以及向System.Drawing.Color和從System.Drawing.Color的隱式轉換。它基於GeekMonkey.com的一個很好的例子。

using System; 
using System.Drawing; 

namespace RMA.Drawing 
{ 
    public class ColorRGB 
    { 
    public byte R; 
    public byte G; 
    public byte B; 
    public byte A; 

    public ColorRGB() 
    { 
     R = 255; 
     G = 255; 
     B = 255; 
     A = 255; 
    } 

    public ColorRGB(Color value) 
    { 
     this.R = value.R; 
     this.G = value.G; 
     this.B = value.B; 
     this.A = value.A; 
    } 

    public static implicit operator Color(ColorRGB rgb) 
    { 
     Color c = Color.FromArgb(rgb.A, rgb.R, rgb.G, rgb.B); 
     return c; 
    } 

    public static explicit operator ColorRGB(Color c) 
    { 
     return new ColorRGB(c); 
    } 

    // Given H,S,L in range of 0-1 
    // Returns a Color (RGB struct) in range of 0-255 
    public static ColorRGB FromHSL(double H, double S, double L) 
    { 
     return FromHSLA(H, S, L, 1.0); 
    } 

    // Given H,S,L,A in range of 0-1 
    // Returns a Color (RGB struct) in range of 0-255 
    public static ColorRGB FromHSLA(double H, double S, double L, double A) 
    { 
     double v; 
     double r, g, b; 

     if (A > 1.0) 
     A = 1.0; 

     r = L; // default to gray 
     g = L; 
     b = L; 
     v = (L <= 0.5) ? (L * (1.0 + S)) : (L + S - L * S); 

     if (v > 0) 
     { 
     double m; 
     double sv; 
     int sextant; 
     double fract, vsf, mid1, mid2; 

     m = L + L - v; 
     sv = (v - m)/v; 
     H *= 6.0; 
     sextant = (int)H; 
     fract = H - sextant; 
     vsf = v * sv * fract; 
     mid1 = m + vsf; 
     mid2 = v - vsf; 

     switch (sextant) 
     { 
      case 0: 
      r = v; 
      g = mid1; 
      b = m; 
      break; 

      case 1: 
      r = mid2; 
      g = v; 
      b = m; 
      break; 

      case 2: 
      r = m; 
      g = v; 
      b = mid1; 
      break; 

      case 3: 
      r = m; 
      g = mid2; 
      b = v; 
      break; 

      case 4: 
      r = mid1; 
      g = m; 
      b = v; 
      break; 

      case 5: 
      r = v; 
      g = m; 
      b = mid2; 
      break; 
     } 
     } 

     ColorRGB rgb = new ColorRGB(); 
     rgb.R = Convert.ToByte(r * 255.0f); 
     rgb.G = Convert.ToByte(g * 255.0f); 
     rgb.B = Convert.ToByte(b * 255.0f); 
     rgb.A = Convert.ToByte(A * 255.0f); 
     return rgb; 
    } 

    // Hue in range from 0.0 to 1.0 
    public float H 
    { 
     get 
     { 
     // Use System.Drawing.Color.GetHue, but divide by 360.0F 
     // because System.Drawing.Color returns hue in degrees (0 - 360) 
     // rather than a number between 0 and 1. 
     return ((Color)this).GetHue()/360.0F; 
     } 
    } 

    // Saturation in range 0.0 - 1.0 
    public float S 
    { 
     get 
     { 
     return ((Color)this).GetSaturation(); 
     } 
    } 

    // Lightness in range 0.0 - 1.0 
    public float L 
    { 
     get 
     { 
     return ((Color)this).GetBrightness(); 
     } 
    } 
    } 
} 

Answer 3

除了secretGeek的回答，擺脫HSL值的顏色（反之亦然），您也可以使用這些本地函數調用（在Visual Basic示例代碼）：

Public Declare Sub ColorRGBToHLS Lib "shlwapi.dll" _ 
            (ByVal clrRGB As UInteger, _ 
            ByRef pwHue As Short, _ 
            ByRef pwLuminance As Short, _ 
            ByRef pwSaturation As Short) 
Public Declare Function ColorHLSToRGB Lib "shlwapi.dll" _ 
             (ByVal wHue As Short, _ 
             ByVal wLuminance As Short, _ 
             ByVal wSaturation As Short) As UInteger 

（在傳遞/接收顏色參數/結果時使用ColorTranslator.ToWin32和ColorTranslator.FromWin32）