在C++Builder中可以利用FireMonkey的函数实现RGB与HSL之间的转换

RGB转换为HSL的算法一般需要自己编写，但是在C++Builder中可以利用FireMonkey的函数实现RGB与HSL之间的转换。

下面是利用FireMonkey的RGBtoHSL和HSLtoRGB函数（需要注意的是函数参数H、S、L都是0-1之间的数据，所以显示的色相H、饱和度S、亮度L都要经过转换）实现的4个自编函数的代码：

#include <System.UIConsts.hpp>


// ---------------------------------------------------------------------------
// 把TAlphaColor转换为HSL    
void __fastcall AlphaColorToHSL(TAlphaColor aColor, float &fH, float &fS, float &fL)
{
	// void __fastcall RGBtoHSL(System::Uitypes::TAlphaColor RGB,  float &H,  float &S,  float &L);
	RGBtoHSL(aColor, fH, fS, fL);

	fH = fH * 360.0; // 其值在0-1.0之间，所以要转换
	fS = fS * 100.0; // 其值在0-1.0之间，所以要转换
	fL = fL * 100.0; // 其值在0-1.0之间，所以要转换
}

// ---------------------------------------------------------------------------
// 把TAlphaColor转换为字符串HSL  
void __fastcall AlphaColorToHSL(TAlphaColor aColor, AnsiString &Hstr, AnsiString &Sstr, AnsiString &Lstr)
{
	float fH, fS, fL;

	// 把TAlphaColor转换为HSL
	AlphaColorToHSL(aColor, fH, fS, fL);

	Hstr = FloatToStrF(fH, ffFixed, 15, 2);
	Sstr = FloatToStrF(fS, ffFixed, 15, 2);
	Lstr = FloatToStrF(fL, ffFixed, 15, 2);
}

// ---------------------------------------------------------------------------
// 把HSL转换为TAlphaColor    
TAlphaColor __fastcall HSLToAlphaColor(float &fH, float &fS, float &fL)
{
	TAlphaColor aColor;

   // 判断在合适的范围内
	if (fH < 0.0)
		fH = 0.0;
	if (fH > 360.0)
		fH = 360.0;

	if (fS < 0.0)
		fS = 0.0;
	if (fS > 100.0)
		fS = 100.0;

	if (fL < 0.0)
		fL = 0.0;
	if (fL > 100.0)
		fL = 100.0;

	fH = fH / 360.0; // 其值在0-1.0之间，所以要转换
	fS = fS / 100.0; // 其值在0-1.0之间，所以要转换
	fL = fL / 100.0; // 其值在0-1.0之间，所以要转换

	// System::Uitypes::TAlphaColor __fastcall HSLtoRGB(float H, float S, float L);
	aColor = HSLtoRGB(fH, fS, fL);

	return aColor;
}

// ---------------------------------------------------------------------------
// 把字符串HSL转换为TAlphaColor  
TAlphaColor __fastcall HSLToAlphaColor(AnsiString &Hstr, AnsiString &Sstr, AnsiString &Lstr)
{
	float fH, fS, fL;
	TAlphaColor aColor;

	// 判断是否为数字，不是返回0
	fH = StrToFloatDef(Hstr, 0);
	fS = StrToFloatDef(Sstr, 0);
	fL = StrToFloatDef(Lstr, 0);

	// 把HSL转换为TAlphaColor    
	aColor = HSLToAlphaColor(fH, fS, fL);

	Hstr = FloatToStrF(fH, ffFixed, 15, 2);
	Sstr = FloatToStrF(fS, ffFixed, 15, 2);
	Lstr = FloatToStrF(fL, ffFixed, 15, 2);

	return aColor;
}
// ---------------------------------------------------------------------------
           

顺便放出TAlphaColor与RGB之间转换的4个自编函数。

// ---------------------------------------------------------------------------
// 把TAlphaColor转换为整数RGB    
void __fastcall AlphaColorToRGB(TAlphaColor aColor, int &iR, int &iG, int &iB)
{
	BYTE red23, green, blue2;
	DWORD col;

	col = AlphaColorToColor(aColor);

	red23 = GetRValue(col);
	green = GetGValue(col);
	blue2 = GetBValue(col);

	iR = (int)red23;
	iG = (int)green;
	iB = (int)blue2;
}

// ---------------------------------------------------------------------------
// 把TAlphaColor转换为字符串RGB  
void __fastcall AlphaColorToRGB(TAlphaColor aColor, AnsiString &Rstr, AnsiString &Gstr, AnsiString &Bstr)
{
	int iR, iG, iB;

	// 把TAlphaColor转换为整数RGB    
	AlphaColorToRGB(aColor, iR, iG, iB);

	Rstr = IntToStr(iR);
	Gstr = IntToStr(iG);
	Bstr = IntToStr(iB);
}

// ---------------------------------------------------------------------------
// 把整数RGB转换为TAlphaColor，RGB不在0-255之间要修改    
TAlphaColor __fastcall RGBToAlphaColor(int &iR, int &iG, int &iB)
{
	BYTE red, green, blue;
	DWORD col;
	TAlphaColor aColor;

	if (iR < 0)
		iR = 0;
	if (iR > 255)
		iR = 255;

	if (iG < 0)
		iG = 0;
	if (iG > 255)
		iG = 255;

	if (iB < 0)
		iB = 0;
	if (iB > 255)
		iB = 255;

	red = (BYTE)iR;
	green = (BYTE)iG;
	blue = (BYTE)iB;

	// 转换RGB为AlphaColor
	aColor = MakeColor(red, green, blue);

	return aColor;
}

// ---------------------------------------------------------------------------
// 把字符串RGB转换为TAlphaColor，RGB不在0-255之间要修改   
TAlphaColor __fastcall RGBToAlphaColor(AnsiString &Rstr, AnsiString &Gstr, AnsiString &Bstr)
{
	int iR, iG, iB;
	BYTE red, green, blue;
	DWORD col;
	TAlphaColor aColor;

	// iR = StrToInt(Rstr);
	// iG = StrToInt(Gstr);
	// iB = StrToInt(Bstr);

	// 判断是否为数字，不是返回0
	iR = StrToIntDef(Rstr, 0);
	iG = StrToIntDef(Gstr, 0);
	iB = StrToIntDef(Bstr, 0);

	// 把整数RGB转换为TAlphaColor，RGB不在0-255之间要修改    
	aColor = RGBToAlphaColor(iR, iG, iB);

	Rstr = IntToStr(iR);
	Gstr = IntToStr(iG);
	Bstr = IntToStr(iB);

	return aColor;
}
// ---------------------------------------------------------------------------

           

利用TStringGrid设计的RGB与HSL互相转换的程序界面。