多个控制点的色条取色算法.cpp

#include<Windows.h>
#include<vector>
#include<algorithm>

struct SpectrumPoint
{
	int p;
	union{
		struct
		{
			BYTE r, g, b, a;
		}rgba;
		COLORREF color;
	};
};

template<size_t count>COLORREF GetSpectrumColor(const SpectrumPoint(&points)[count],int v)
{
	std::vector<SpectrumPoint>pointList(points, points + count);
	std::sort(pointList.begin(), pointList.end(), [](SpectrumPoint a, SpectrumPoint b){return a.p < b.p; });
	if (pointList.begin()->p > v)
		return pointList.begin()->color;
	for (std::vector<SpectrumPoint>::iterator itPointList = pointList.begin(); itPointList != pointList.end(); itPointList++)
	{
		if (itPointList->p > v)
		{
			std::vector<SpectrumPoint>::iterator itPointListStart = itPointList - 1;
			return RGB(itPointListStart->rgba.r + (itPointList->rgba.r - itPointListStart->rgba.r)*(v - itPointListStart->p) / (itPointList->p - itPointListStart->p),
				itPointListStart->rgba.g + (itPointList->rgba.g - itPointListStart->rgba.g)*(v - itPointListStart->p) / (itPointList->p - itPointListStart->p),
				itPointListStart->rgba.b + (itPointList->rgba.b - itPointListStart->rgba.b)*(v - itPointListStart->p) / (itPointList->p - itPointListStart->p));
		}
	}
	return pointList.back().color;
}