我需要通过引入反锯齿线来升级一个旧的VCL图形应用程序。为此，我用C编写了https://en.wikipedia.org/wiki/Xiaolin_Wu%27s_line_algorithm页中指出的算法。代码如下。不幸的是，我没有找到任何方法或手段来推导C Builder的“亮度”，不同颜色的亮度如何？

//Antialiased line:
void Observer::aaLine(int x0, int y0, int x1, int y1)
{
    //Draws the pixel point (x,y) with specified brightness, 0 <= br <= 1 :
    auto plot = [&](double X, double Y, double brighness){
        pC->Pixels[X][Y] = brightness; };

    //Fractional part of x:
    auto fpart  = [](double x) { return x - floor(x); };
    auto rfpart = [&](double x) { return 1 - fpart(x); };

    bool steep = abs(y1 - y0) > abs(x1 - x0);

    if(steep) {
        std::swap(x0, y0);
        std::swap(x1, y1);
    }

    if( x0 > x1 ) {
        std::swap(x0, x1);
        std::swap(y0, y1);
    }

    auto dx = x1 - x0;
    auto dy = y1 - y0;
    double gradient;

    if( dx == 0.0 )
        gradient = 1.0;
    else
        gradient = dy / dx;

    //Handle first endpoint
    auto xend = round(x0),
         yend = y0 + gradient * (xend - x0),
         xgap = rfpart(x0 + 0.5),
         xpxl1 = xend, // this will be used in the main loop
         ypxl1 = floor(yend);

    if( steep ) {
        plot(ypxl1,   xpxl1, rfpart(yend) * xgap);
        plot(ypxl1+1, xpxl1,  fpart(yend) * xgap);
    }
    else {
        plot(xpxl1, ypxl1  , rfpart(yend) * xgap);
        plot(xpxl1, ypxl1+1,  fpart(yend) * xgap);
    }
    auto intery = yend + gradient; // first y-intersection for the main loop

    //Handle second endpoint
    xend = round(x1);
    yend = y1 + gradient * (xend - x1);
    xgap = fpart(x1 + 0.5);
    auto xpxl2 = xend, //this will be used in the main loop
         ypxl2 = floor(yend);
    if( steep ){
        plot(ypxl2  , xpxl2, rfpart(yend) * xgap);
        plot(ypxl2+1, xpxl2,  fpart(yend) * xgap);
    }
    else {
        plot(xpxl2, ypxl2,  rfpart(yend) * xgap);
        plot(xpxl2, ypxl2+1, fpart(yend) * xgap);
    }

    //Main loop:
    if( steep )
        for(double x = xpxl1 + 1 ; x <= xpxl2 - 1 ; x += 1)
        {
            plot(floor(intery)  , x, rfpart(intery));
            plot(floor(intery)+1, x,  fpart(intery));
            intery += gradient;
        }
    else
        for(double x = xpxl1 + 1 ; x <= xpxl2 - 1 ; x += 1)
        {
            plot(x, floor(intery),  rfpart(intery));
            plot(x, floor(intery)+1, fpart(intery));
            intery += gradient;
        }
}//Observer::aaLine.

问题位于（我相信）函数的lambda顶部。非常感谢。