Question

我有绘制饼图的中心点，半径和角度，但the Pie function需要4个点作为输入数据。有没有人有任何转换功能或更好的解释？

Answer 1

派对功能中的四点：

边界矩形的左上角。
边界矩形的右下角。
指向标记饼图开头的圆圈。
指向标记饼图末端的圆圈（逆时针）。

转换：

中心点：Cx，Cy 半径：r 角度：a

假设你的馅饼从顶部开始。

X1 = Cx-r，Y1 = Cx + r
X2 = Cx + r，Y2 = Cy-r
X3 = Cx，Y3 = Y1
X4 = Cx + r sin（a），Y4 = Cy + r cos（a）

你可能不得不在某个地方翻转一个标志，但这应该可以解决问题。

有两个不同的天使（a和b）：

X3 = Cx + r sin（a），Y3 = Cy + r cos（a）
X4 = Cx + r sin（b），Y4 = Cy + r cos（b）

Answer 2

这是用（旧）C ++编写的，但大多数应该很容易转换为Delphi（或几乎其他任何东西）。它还假设输入是百分比（整圆是100％）而不是原始角度，但（再次）应该很容易处理。它具有从百分比到角度的弧度转换，因此从其他单位转换应该是非常简单的调整。

class section {
    double percent;
    int color;
public:

    section(double percent_, int color_) :
        percent(percent_), color(color_) {}

    void draw(HDC destination, POINT const &center, int diameter, double &start_angle);
};

void section::draw(HDC destination, POINT const &center, int radius, double &start_angle) {

    double start_x, start_y, end_x, end_y;
    double angle, end_angle;

    int top = center.y - radius;
    int bottom = center.y + radius;
    int left = center.x - radius;
    int right = center.x + radius;

    // now we have to convert a percentage to an angle in radians.
    // there are 100 percent in a circle, and 2*PI radians in a
    // circle, so we figure this percentage of 2*PI radians.
    angle = percent / 100.0 * 2.0 * 3.1416;

    end_angle = start_angle + angle;

    // Now we have to convert these angles into rectangular
    // coordinates in the window, which depend on where we're
    // putting the chart, and how big we're making it.
    start_x = center.x + radius * cos(start_angle);
    start_y = center.y + radius * sin(start_angle);

    end_x = center.x + radius * cos(end_angle);
    end_y = center.y + radius * sin(end_angle);

    // Now we need to actually draw the pie section by selecting
    // the correct color into the DC, drawing the section, then
    // selecting the original brush back, and deleing our brush.
    HBRUSH brush = CreateSolidBrush(color);

    HBRUSH old_brush = (HBRUSH)SelectObject(destination, brush);

    Pie(destination, left, top, right, bottom, 
        (int)start_x, (int)start_y, (int)end_x, (int)end_y);

    SelectObject(destination, old_brush);
    DeleteObject(brush);

    // our sole awareness of other sections: the next section will
    // start wherever we finished.
    start_angle = end_angle;
}

如何调用Pie函数？

2 个答案: