Dynamic Color Spectrum

#include <d3d9.h>

class D3DColorSpectrum
{
	LPDIRECT3DDEVICE9 pDevice;
	LPDIRECT3DTEXTURE9 pTex;
	int Width;
	int Height;

	D3DCOLOR HSLToRGB(float H, float S, float L);
public:
	D3DColorSpectrum();
	~D3DColorSpectrum();

	HRESULT Init(LPDIRECT3DDEVICE9 _pDevice, int _Width, int _Height);
	void Destroy();

	LPDIRECT3DTEXTURE9 GetTex();

	D3DCOLOR GetColor(int X, int Y);
};

#include "D3DColorSpectrum.h"

D3DColorSpectrum::D3DColorSpectrum() : pDevice(0), pTex(0), Width(1), Height(1)
{}

D3DColorSpectrum::~D3DColorSpectrum()
{
	Destroy();
}

D3DCOLOR D3DColorSpectrum::HSLToRGB(float H, float S, float L)
{
	float Q;
	if (L < 0.5f)
		Q = L * (S + 1.0f);
	else
		Q = L + S - (L * S);

	float P = 2 * L - Q;

	float RGBs[3];
	RGBs[0] = H + (1.0f / 3.0f);
	RGBs[1] = H;
	RGBs[2] = H - (1.0f / 3.0f);

	for (int i = 0; i < 3; ++i)
	{
		if (RGBs[i] < 0)
			RGBs[i] += 1.0f;
		if (RGBs[i] > 1)
			RGBs[i] -= 1.0f;

		if (RGBs[i] < (1.0f / 6.0f))
			RGBs[i] = P + ((Q - P) * 6 * RGBs[i]);
		else if (RGBs[i] < 0.5f)
			RGBs[i] = Q;
		else if (RGBs[i] < (2.0f / 3.0f))
			RGBs[i] = P + ((Q - P) * 6 * ((2.0f / 3.0f) - RGBs[i]));
		else
			RGBs[i] = P;
	}

	return D3DCOLOR_XRGB(int(RGBs[0] * 255.0f), int(RGBs[1] * 255.0f), int(RGBs[2] * 255.0f));
}

HRESULT D3DColorSpectrum::Init(LPDIRECT3DDEVICE9 _pDevice, int _Width, int _Height)
{
	pDevice = _pDevice;
	Width = _Width;
	Height = _Height;

	bool Bits32 = true;
	HRESULT hr;
	hr = pDevice->CreateTexture(Width, Height, 1, 0, D3DFMT_X8R8G8B8, D3DPOOL_MANAGED, &pTex, 0);
	if (FAILED(hr))
	{
		Bits32 = false;
		hr = pDevice->CreateTexture(Width, Height, 1, 0, D3DFMT_X4R4G4B4, D3DPOOL_MANAGED, &pTex, 0);
		if (FAILED(hr))
			return hr;
	}

	D3DLOCKED_RECT lrc;
	hr = pTex->LockRect(0, &lrc, 0, 0);
	if (FAILED(hr))
	{
		pTex->Release();
		pTex = 0;
		return hr;
	}

	float H = 0;
	float S = 0.99f;
	float L = 1.0f;

	D3DCOLOR Color;

	BYTE R;
	BYTE G;
	BYTE B;

	DWORD* pColors32 = ((DWORD*) lrc.pBits) - 1;
	WORD* pColors = ((WORD*) lrc.pBits) - 1;

	for (int i = 0; i < Width; ++i)
	{
		for (int j = 0; j < Height; ++j)
		{
			Color = HSLToRGB(H, S, L);
			if (Bits32)
			{
				pColors32++;
				*pColors32 = Color;//(0xFF << 24) | (R << 16) | (G << 8) | (B << 0);
			}
			else
			{
				R = ((Color >> 16) & 0xFF) / 0x10;
				G = ((Color >> 8) & 0xFF) / 0x10;
				B = ((Color >> 0) & 0xFF) / 0x10;
				pColors++;
				*pColors = (0xFF << 12) | (R << 8) | (G << 4) | (B << 0);
			}
			H += (1.0f / Width);
		}
		L -= (1.0f / Height);
		H = 0.0f;
	}

	pTex->UnlockRect(0);

	return S_OK;
}

void D3DColorSpectrum::Destroy()
{
	if (pTex != 0)
	{
		pTex->Release();
		pTex = 0;
	}
}

LPDIRECT3DTEXTURE9 D3DColorSpectrum::GetTex()
{
	return pTex;
}

D3DCOLOR D3DColorSpectrum::GetColor(int X, int Y)
{
	float H = X * (1.0f / Width);
	float S = 0.99f;
	float L = 1.0f - Y * (1.0f / Height);
	return HSLToRGB(H, S, L);
}

ColorSpectrum.Init(pDevice, Width, Height);

pSprite->Draw(ColorSpectrum.GetTex(), ...);

POINT pt;
GetCursorPos(&pt);

D3DCOLOR ClickedColor = ColorSpectrum.GetColor(pt.x - SpectrumX, pt.y - SpectrumY);