// 以下是项目中的一段热点代码
// 会调用这个函数很多次，用来计算亚像素的像素值，方法是插值（具体算法可以不用管），里头的具体魔数我改了一下，因为是公司的代码，而且跟优化没有关系
double GetSubPixelValue(const double* preCaculatedParameter, int width, int height, double X, double Y)
{
int xIndex[6], yIndex[6];
xIndex[0] = int(X + 0.5) - 2;
yIndex[0] = int(Y + 0.5) - 2;
for (int i = 1; i < 5; i++)
{
xIndex[i] = xIndex[i - 1] + 1;
yIndex[i] = yIndex[i - 1] + 1;
}
double xWeight[5];
{
double w = X - (double)xIndex[2];
double w2 = w * w;
double w3 = w * w2;
double w4 = w2 * w2;
xWeight[0] = 0.111 * w4 - w3 / 22.0 + 0.233 * w2 - 0.344 * w + 0.345;
xWeight[1] = -0.333 * w4 + 0.333 * w3 + 0.444 * w2 - 0.555 * w + 0.0666;
xWeight[2] = 0.15 *w4 - 0.222 * w2 + 0.0777;
xWeight[3] = -0.333 * w4 - 0.333 * w3 + 0.444 * w2 + 0.555 * w + 0.0666;
xWeight[4] = 0.111 * w4 + w3 / 22.0 + 0.233 * w2 + 0.344 * w + 0.345;
}
// 下面这个计算方法和上面是一样的
double yWeight[5];
{
double w = Y - (double)yIndex[2];
double w2 = w * w;
double w3 = w * w2;
double w4 = w2 * w2;
yWeight[0] = 0.111 * w4 - w3 / 22.0 + 0.233 * w2 - 0.344 * w + 0.345;
yWeight[1] = -0.333 * w4 + 0.333 * w3 + 0.444 * w2 - 0.555 * w + 0.0666;
yWeight[2] = 0.15 *w4 - 0.222 * w2 + 0.0777;
yWeight[3] = -0.333 * w4 - 0.333 * w3 + 0.444 * w2 + 0.555 * w + 0.0666;
yWeight[4] = 0.111 * w4 + w3 / 22.0 + 0.233 * w2 + 0.344 * w + 0.345;
}
int width2 = 2 * width - 2;
int height2 = 2 * height - 2;
for (int i = 0; i < 5; i++)
{
xIndex[i] = (xIndex[i] < 0) ? (-xIndex[i] - width2 * ((-xIndex[i]) / width2)) : (xIndex[i] - width2 * (xIndex[i] / width2));
if (width <= xIndex[i])
xIndex[i] = width2 - xIndex[i];
yIndex[i] = (yIndex[i] < 0) ? (-yIndex[i] - height2 * ((-yIndex[i]) / height2)) : (yIndex[i] - height2 * (yIndex[i] / height2));
if (height <= yIndex[i])
yIndex[i] = height2 - yIndex[i];
}
double result = 0;
for (int i = 0; i < 5; i++)
{
for (int j = 0; j < 5; j++)
{
result += ((*(preCaculatedParameter + width * yIndex[i] + xIndex[j])) * xWeight[j] * yWeight[i]);
}
}
return result;
}
#include <vector>
#include <chrono>
#include <iostream>
#define TICK(x) auto bench_##x = std::chrono::steady_clock::now();
#define TOCK(x) std::cerr<<#x ": "<<std::chrono::duration_cast<std::chrono::duration<double>>(std::chrono::steady_clock::now()-bench_##x).count();std::cerr<<"秒\n";
#define TEST_NUM 10000000
int main() {
int width = 2048;
int height = 2048;
std::vector<double> preCaculatedParameter(width * height, 0.123); // 里面是预计算的数字
std::vector<double> xs(TEST_NUM);
std::vector<double> ys(TEST_NUM);
for (size_t i = 0; i < xs.size(); i++)
{
xs[i] = rand() % 2048;
ys[i] = rand() % 2048;
}
std::vector<double> result(1);
TICK(t);
for (int i = 0; i < TEST_NUM; i++)
{
result[0] = GetSubPixelValue(preCaculatedParameter.data(), width, height, xs[i], ys[i]);
}
TOCK(t);
return 0;
}
